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PHYSICS (579 journals)

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Journal Cover Physics and Chemistry of the Earth, Parts A/B/C
  [SJR: 0.611]   [H-I: 26]   [6 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1474-7065
   Published by Elsevier Homepage  [3043 journals]
  • Wetland biogeochemistry and ecological risk assessment
    • Authors: Junhong Bai; Laibin Huang; Haifeng Gao; Guangliang Zhang
      Pages: 1 - 2
      Abstract: Publication date: February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 97
      Author(s): Junhong Bai, Laibin Huang, Haifeng Gao, Guangliang Zhang


      PubDate: 2017-03-01T21:11:12Z
      DOI: 10.1016/j.pce.2017.02.004
      Issue No: Vol. 97 (2017)
       
  • Effects of salinity on dynamics of soil carbon in degraded coastal
           wetlands: Implications on wetland restoration
    • Authors: Qingqing Zhao; Junhong Bai; Qiongqiong Lu; Guangliang Zhang
      Pages: 12 - 18
      Abstract: Publication date: February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 97
      Author(s): Qingqing Zhao, Junhong Bai, Qiongqiong Lu, Guangliang Zhang
      To investigate the effects of salinity on dynamics of soil carbon contents and stocks, soil samples were collected at a depth of 30 cm at four sampling sites (Sites B, T, S and P) along a salinity gradient in a drained coastal wetland, the Yellow River Delta, China. The salinity of these four sites ranked in the order: B (8.68 ± 4.25 ms/cm) > T (5.89 ± 3.17 ms/cm) > S (3.19 ± 1.01 ms/cm) > P (2.26 ± 0.39 ms/cm). Soil total carbon (TC), soil organic carbon (SOC), and soil microbial biomass carbon (MBC) were measured. Based on these data, soil organic carbon density (SOCD) and soil microbial biomass carbon density (MBCD) were calculated at four sites. The results showed that the mean concentrations of TC and MBC showed a general deceasing tendency with increasing salinities in the top 30 cm of soils. The values of SOCD and MBCD exhibited similar tendency along the salinity gradient. As for profile distribution pattern, The C/N ratios ranged from 8.28 to 56.51. The microbial quotient values at four sampling sites were quite low, ranging from 0.06 to 0.19. Higher C/N ratios were found in samples with high salinity. Correlation analysis showed that the concentrations of TC and MBC at four sampling sites were significantly negatively correlated with salinity (P < 0.01 or P < 0.05), indicating that salinity could inhibit soil carbon accumulation and microbial activities.

      PubDate: 2017-03-01T21:11:12Z
      DOI: 10.1016/j.pce.2016.08.008
      Issue No: Vol. 97 (2017)
       
  • Seasonal variation in pans in relation to limno-chemistry, size,
           hydroperiod, and river connectivity in a semi-arid subtropical region
    • Authors: Tamuka Nhiwatiwa; Tatenda Dalu
      Pages: 37 - 45
      Abstract: Publication date: February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 97
      Author(s): Tamuka Nhiwatiwa, Tatenda Dalu
      Seasonal pans are hydrologically dynamic, with significant changes in water volume and depth in response to high evaporation, infiltration rates and inundation events. Intra-seasonal and inter-seasonal changes in endorheic and floodplain pans in relation to limnology, size, hydroperiod, and river connectivity were studied over two rainfall seasons across 36 pans at the Save Valley Conservancy. In the study region, floodplain pans were identified as pans that had connectivity with the Save River, while the endorheic pans (large and small) were hydrologically isolated basins. Seasonal trends for physico-chemical variables were initial low and gradual increased for both rainfall seasons. Significant inter-seasonal differences for several physico-chemical variables were observed. No significant differences in physico-chemical variables were observed between large and small endorheic pans, with the except for vegetation cover, which was higher in large pans. Floodplain pans differed from the endorheic systems in pH, conductivity, nutrients and suspended solids. Connectivity was found to be insignificant, as connections between these systems were probably too infrequent. Seasonal pans were uniquely distinguished by their morphometric, physico-chemical and hydrological characteristics. Inevitably, they are vulnerable to climate change with the extent of their resilience currently unknown.

      PubDate: 2017-03-01T21:11:12Z
      DOI: 10.1016/j.pce.2016.11.003
      Issue No: Vol. 97 (2017)
       
  • Heavy metals pollution in soil profiles from seasonal-flooding riparian
           wetlands in a Chinese delta: Levels, distributions and toxic risks
    • Authors: Guangliang Zhang; Junhong Bai; Qingqing Zhao; Jia Jia; Xiaojun Wen
      Pages: 54 - 61
      Abstract: Publication date: February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 97
      Author(s): Guangliang Zhang, Junhong Bai, Qingqing Zhao, Jia Jia, Xiaojun Wen
      Soil profile samples were collected in seasonal-flooding riparian wetlands in the Yellow River Delta (YRD) of China in autumn and spring to investigate the levels, distributions and toxic risks of heavy metals in soil profiles. Total elemental contents of Al, As, Cd, Cr, Cu, Ni, Pb and Zn were determined using inductively coupled plasma atomic absorption spectrometry (ICP-AAS). Results indicated that the contents of determined heavy metals showed non-negligible depth variations (coefficient of variation > 10%), and their distribution patterns were irregular. Compared with other heavy metals, both As and Cd presented higher enrichment factors (EF) based on the classification of EF values (moderate enrichment for As while significant enrichment for Cd). Cluster analysis (CA) and principal components analysis (PCA) revealed that Cr, Cu, Ni, Pb and Zn might derive from the common source, while As and Cd shared another similar source. The toxic unit (TU) values of these heavy metals did not exceed probable effect levels (PEL) except for Ni. Both As and Ni showed higher contributions to the sum of TU (∑TUs), which indicated they were the primary concerns of heavy metals pollution. Generally, As, Cd and Ni should be paid more attention for wetlands managers and policy makers to avoid potential ecotoxicity in the study area. The findings of this study could contribute to the prevention and control of heavy metals pollution in estuarine wetlands.

      PubDate: 2017-03-01T21:11:12Z
      DOI: 10.1016/j.pce.2016.11.004
      Issue No: Vol. 97 (2017)
       
  • Impact of salinity and Pb on enzyme activities of a saline soil from the
           Yellow River delta: A microcosm study
    • Authors: Lidi Zheng; Mingxiang Zhang; Rong Xiao; Jingxiao Chen; Feihai Yu
      Pages: 77 - 87
      Abstract: Publication date: February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 97
      Author(s): Lidi Zheng, Mingxiang Zhang, Rong Xiao, Jingxiao Chen, Feihai Yu
      Soil enzyme activities are sensitive to the changes of soil properties and pollutants. In this study, the influence of salinity and Pb on the soil enzyme (catalase, CAT; invertase, IA; urease, UA) activities regarding the soil aggregate size classes was investigated. We selected a saline soil from the Yellow River delta, and adopted an orthogonal experiment designed with five Pb concentration levels and five salinity levels. The soil was dry sieved into three soil aggregate size classes: >2000 μm, 250–2000 μm, and <250 μm. All three enzyme activities significantly decreased with the increase of soil salinity (P < 0.05). Pb had an inhibition effect on IA and UA activities but a significant promoting effect on CAT activity (P < 0.05) within the concentration range of 0–400 mg kg−1. When Pb concentration exceeded 400 mg kg−1, with the increase of Pb concentration, there were no significant changes of all the enzyme activities under the inhibition or promotion effects of Pb. The Pb concentration which leads to a significant reduction is between 0 and 200 mg kg−1 for IA activity and 200–400 mg kg−1 for UA activity. And the increase of soil salinity led to a higher toxicity of Pb for UA activity. The toxicity range could be a valid reference for the formulation of soil quality standards in estuarine wetlands. We concluded that the effects of Pb on soil enzyme activities depend on the Pb concentration, soil salinity and the enzyme types. IA activity showed a higher activity in the macro-aggregate (250–2000 μm), while there was no significant difference in CAT and UA activities among three particle size classes. Since the IA activity was sensitive to soil salinity, Pb concentration and soil aggregate size, it could be selected as a representative indicator for soil monitoring in the Yellow River delta.

      PubDate: 2017-03-01T21:11:12Z
      DOI: 10.1016/j.pce.2016.11.001
      Issue No: Vol. 97 (2017)
       
  • Exploration of the causality between area changes of green spaces and
           waterlogging frequency in Beijing
    • Authors: Guofeng Wang; Jiancheng Chen; Chunhong Zhao; Xiaoxue Zhou; Xiangzheng Deng
      Abstract: Publication date: Available online 7 March 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Guofeng Wang, Jiancheng Chen, Chunhong Zhao, Xiaoxue Zhou, Xiangzheng Deng


      PubDate: 2017-03-08T21:16:13Z
      DOI: 10.1016/j.pce.2017.03.001
       
  • The study on ecological sustainable development in Chengdu
    • Authors: Yifan Li; Jinyan Zhan; Fan Zhang; Miaolin Zhang; Dongdong Chen
      Abstract: Publication date: Available online 6 March 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Yifan Li, Jinyan Zhan, Fan Zhang, Miaolin Zhang, Dongdong Chen
      Ecological footprint is one of the important methods to study ecological sustainable development, but ecological footprint focuses on only the static calculation of ecological sustainable development and cannot dynamically predict its development. In this study, we combine ecological footprint with system dynamics software STELLA to construct a predictable model of ecological sustainable development. We introduce rate1 and rate2 into the model, which reflects the change in per capita consumption of biological resources and energy due to the socio-economic development, and by changing the values of them to simulate a variety of scenarios. The results show that ecological sustainable development of Chengdu is in the state of ecological deficit, which is 1.43 million hm2 in 2013, and different rate1 and rate2 will lead to different changes in the ecological deficit. When rate1=rate2=0.1, the degree of ecological deficit in Chengdu is reduced from 1.43 million hm2 to 1.24 million hm2 in 2013-2018, and after 2018, it begins to increase, which will reach 1.32 million hm2 in 2021. And when rate1=rate2=0.05, the ecological deficit of Chengdu in 2013-2021 will decrease gradually, which from 1.43 million hm2 to 1.31 million hm2. These results reflect the impact of economic development on ecological sustainable development, and it can provide a reference for the balanced development of economic and ecological protection, which will help decision makers to do something for ecological sustainable development planning of Chengdu.

      PubDate: 2017-03-08T21:16:13Z
      DOI: 10.1016/j.pce.2017.03.002
       
  • Assessment of the content, structure, and source of soil dissolved organic
           matter in the coastal wetlands of Jiaozhou Bay, China
    • Authors: Min Xi; Yuanyuan Zi; Qinggai Wang; Sen Wang; Guolu Cui; Fanlong Kong
      Abstract: Publication date: Available online 6 March 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Min Xi, Yuanyuan Zi, Qinggai Wang, Sen Wang, Guolu Cui, Fanlong Kong
      The contents and structure of dissolved organic matter (DOM) in four typical wetlands, such as naked tidal, suaeda salsa, reed and spartina, were conducted to investigate the content, structure, and source of dissolved organic matter in coastal wetland soil. The soil samples were obtained from Jiaozhou Bay in January, April, July, and October of 2014. Results showed that the DOM contents in soil of four typical wetland were in order of spartina wetland > naked tidal > suaeda salsa wetland > reed wetland in horizontal direction, and decreased with the increase of soil depth on vertical section. In addition, the DOM contents changed with the seasons, in order of spring > summer > autumn > winter. The structural characteristics of DOM in Jiaozhou Bay wetland, such as aromaticity, hydrophobicity, molecular weight, polymerization degree of benzene ring carbon frame structure and so on were in order of spartina wetland > naked tidal > suaeda salsa wetland > reed wetland in the horizontal direction. On the vertical direction, they showed a decreasing trend with the increase of soil depth. The results of three dimensional fluorescence spectra and fluorescence spectrum parameters (FI, HIX, and BIX) indicated that the DOM in Jiaozhou Bay was mainly derived from the biological activities. The contents and structure of DOM had certain relevance, but the contents and source as well as the structure and source of DOM had no significant correlation. The external pollution including domestic sewage, industrial wastewater, and aquaculture sewage affected the correlation among the content, structure and source of DOM by influencing the percentage of non-fluorescent substance in DOM and disturbing the determination of protein-like fluorescence.

      PubDate: 2017-03-08T21:16:13Z
      DOI: 10.1016/j.pce.2017.03.004
       
  • Prediction of non-linear site response using downhole array data and
           numerical modeling: The Belleplaine (Guadeloupe) case study
    • Authors: Luis Fabian Bonilla; Philippe Guéguen; Fernando Lopez-Caballero; E. Diego Mercerat; Céline Gélis
      Abstract: Publication date: Available online 28 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Luis Fabian Bonilla, Philippe Guéguen, Fernando Lopez-Caballero, E. Diego Mercerat, Céline Gélis
      In this study, we analyze the acceleration time histories data at the Belleplaine (Guadeloupe, French West Indies) vertical array, recorded between 2008 and 2014, to evaluate the seismic response of sediments. First, we apply seismic interferometry by deconvolution method to compute the in-situ shear wave velocity between the sensor at the surface and the two shallow sensors located at GL-15m and GL-39m depth. The efficiency of this method is discussed by studying the variability of the velocity profile obtained and comparing with the in-situ geophysical survey of the site. Computed strains between sensors remain very weak, lower than 10-5, meaning that nonlinearities are not expected for these events. Moreover, the small dispersion of shear wave velocities values deduced from seismic interferometry may be related to the elastic behavior of the soil column. Furthermore, the transfer functions between each sensor combination are inverted to obtain a new velocity profile compatible with the geological knowledge of the site. The lag times calculated by seismic interferometry are then used to constrain random perturbations of the inverted velocity profile, allowing to study the variability of the 1D soil response. Since recorded motion has a PGA less than 10 cm/s2 in the dataset, we numerically predict the nonlinear response of the site using strong motion from a worldwide dataset. Furthermore, we study the ratio between the PGV and the medium shear velocity as a proxy showing the development of shear deformation during strong motion. Finally, using strong motion events from a worldwide dataset, we numerically predict the nonlinear response of the site based on shear wave velocity variation and the strain proxy computed by the particle velocity versus shear wave velocity ratio. We conclude that seismic interferometry by deconvolution is a robust and accurate solution to help extracting the shear wave velocity profile and to monitor the soil nonlinear response. This technique can be used when strong earthquakes will be recorded at this experimental site in order to track and assess nonlinear effects in the soil column.

      PubDate: 2017-03-01T21:11:12Z
      DOI: 10.1016/j.pce.2017.02.017
       
  • Green space water use and its impact on water resources in the capital
           region of China
    • Authors: Feng
      Abstract: Publication date: Available online 24 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Mi Feng


      PubDate: 2017-03-01T21:11:12Z
       
  • Remote sensing leaf water stress in coffee (Coffea arabica) using
           secondary effects of water absorption and random forests
    • Authors: Abel Chemura; Onisimo Mutanga; Timothy Dube
      Abstract: Publication date: Available online 23 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Abel Chemura, Onisimo Mutanga, Timothy Dube
      Water management is an important component in agriculture, particularly for perennial tree crops such as coffee. Proper detection and monitoring of water stress therefore plays an important role not only in mitigating the associated adverse impacts on crop growth and productivity but also in reducing expensive and environmentally unsustainable irrigation practices. Current methods for water stress detection in coffee production mainly involve monitoring plant physiological characteristics and soil conditions. In this study, we tested the ability of selected wavebands in the VIS/NIR range to predict plant water content (PWC) in coffee using the random forest algorithm. An experiment was set up such that coffee plants were exposed to different levels of water stress and reflectance and plant water content measured. In selecting appropriate parameters, cross-correlation identified 11 wavebands, reflectance difference identified 16 and reflectance sensitivity identified 22 variables related to PWC. Only three wavebands (485nm, 670nm and 885nm) were identified by at least two methods as significant. The selected wavebands were trained (n=36) and tested on independent data (n=24) after being integrated into the random forest algorithm to predict coffee PWC. The results showed that the reflectance sensitivity selected bands performed the best in water stress detection (r = 0.87, RMSE = 4.91% and pBias = 0.9%), when compared to reflectance difference (r = 0.79, RMSE = 6.19 and pBias=2.5%) and cross-correlation selected wavebands (r = 0.75, RMSE = 6.52 and pBias = 1.6). These results indicate that it is possible to reliably predict PWC using wavebands in the VIS/NIR range that correspond with many of the available multispectral scanners using random forests and further research at field and landscape scale is required to operationalize these findings.

      PubDate: 2017-03-01T21:11:12Z
      DOI: 10.1016/j.pce.2017.02.011
       
  • Evaluating the influence of the Red Edge band from RapidEye sensor in
           quantifying leaf area index for hydrological applications specifically
           focusing on plant canopy interception
    • Authors: Timothy Dube; Onisimo Mutanga; Mbulisi Sibanda; Cletah Shoko; Abel Chemura
      Abstract: Publication date: Available online 22 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Timothy Dube, Onisimo Mutanga, Mbulisi Sibanda, Cletah Shoko, Abel Chemura
      Reliable and accurate quantification of plant Leaf Area Index (LAI) is critical in understanding its role in reducing runoff. The main aim of the present study was to evaluate the ability of the Red Edge (RE) band derived from RapidEye in estimating LAI for applications in quantifying canopy interception at landscape scale. To achieve this objective, the study also compares the predictive power of two machine learning algorithms (Random Forest-RF and Stochastic Gradient Boosting-SGB) in estimating LAI. Comparatively, the results of the study have demonstrated that the inclusion of spectral information derived from the Red Edge band yields high accurate LAI estimates, when compared to the use of traditional traditional Red, Green, Blue and Near Infra-Red (traditional RGBNIR) spectral information. The results indicate that the use of the four traditional RGBNIR bands yielded comparatively lower R2 values and high Root Mean Squares, Mean Absolute Error (Pinus taeda: R2 of 0.60; the lowest RMSE (0.35 m2/m2) and MAE of 28); whereas the use of integration of traditional RGBNIR+RE in more accurate LAI estimates (Pinus taeda: R2 = 0.65; RMSE = 0.30 m2/m2) and the lowest MAE of 0.23). These findings therefore underscores the importance of new generation multispectral sensors with strategically-position bands and machine learning algorithms in estimating LAI for quantifying canopy interception, especially in resource-poor areas.

      PubDate: 2017-02-22T20:52:05Z
      DOI: 10.1016/j.pce.2017.02.016
       
  • Assessment of water availability for competing uses using SWAT and WEAP in
           South Phuthiatsana catchment, Lesotho
    • Authors: Motlatsi Maliehe; Deogratias M.M. Mulungu
      Abstract: Publication date: Available online 21 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Motlatsi Maliehe, Deogratias M.M. Mulungu
      The study assessed the quantity of surface water in the South Phuthiatsana catchment, estimated flows in ungauged catchments using Soil and Water Assessment Tool (SWAT) and allocated the resources in the catchment using Water Evaluation And Planning (WEAP) model. SWAT model was calibrated from 1979 to 2001, the p-factor was 65%, r_factor 0.58, NS 0.59 and R2 0.59 for calibration and for validation from 2002 to 2013, the p-factor was 57%, the r_factor was 1.34, the NS was 0.52, and R2 was 0.66. The results show the water balance as: 26% of precipitation form streamflow, 41% of the total flow comes from baseflow, while surface runoff accounts for 59%, 14% of precipitation percolates to shallow aquifer, 1% percolates to deep aquifer and 68% of precipitation is lost through evapotranspiration. The WEAP model was calibrated using CG024 and CG084 stations and historical demands. For CG024 calibration (1972 – 2002) NS was 0.72 and R2 was 0.84 and for validation (2003 – 2014) the NS was 0.73 and R2 was 0.74. For CG084 calibration (2007 – 2011) NS and R2 were 0.55 and 0.64 and for validation (2012 – 2014) the NS and R2 were 0.63 and 0.89 respectively. Two scenarios were evaluated. First for the reference scenario, the Metolong industrial demands of 1.46 Mm3 and environmental demands of 2.29 Mm3 were both not met. Secondly, for the irrigation expansion scenario, increasing irrigation land by 12.3%, a total of 4.44 Mm3 demands were not met (irrigation accounts for 65.65% of the unmet). Therefore, the study recommends an irrigation plan for the catchment. The irrigation plan has to include: irrigation systems designed for the site, meteorological stations and an irrigator’s association with experts forming part of the board.

      PubDate: 2017-02-22T20:52:05Z
      DOI: 10.1016/j.pce.2017.02.014
       
  • Providing peak river flow statistics and forecasting in the Niger River
           basin
    • Authors: Jafet C.M. Andersson; Abdou Ali; Berit Arheimer; David Gustafsson; Bernard Minoungou
      Abstract: Publication date: Available online 21 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Jafet C.M. Andersson, Abdou Ali, Berit Arheimer, David Gustafsson, Bernard Minoungou
      Flooding is a growing concern in West Africa. Improved quantification of discharge extremes and associated uncertainties is needed to improve infrastructure design, and operational forecasting is needed to provide timely warnings. In this study, we use discharge observations, a hydrological model (Niger-HYPE) and extreme value analysis to estimate peak river flow statistics (e.g. the discharge magnitude with a 100-year return period) across the Niger River basin. To test the model’s capacity of predicting peak flows, we compared 30-year maximum discharge and peak flow statistics derived from the model vs. derived from nine observation stations. The results indicate that the model simulates peak discharge reasonably well (on average +20%). However, the peak flow statistics have a large uncertainty range, which ought to be considered in infrastructure design. We then applied the methodology to derive basin-wide maps of peak flow statistics and their associated uncertainty. The results indicate that the method is applicable across the hydrologically active part of the river basin, and that the uncertainty varies substantially depending on location. Subsequently, we used the most recent bias-corrected climate projections to analyze potential changes in peak flow statistics in a changed climate. The results are generally ambiguous, with consistent changes only in very few areas. To test the forecasting capacity, we ran Niger-HYPE with a combination of meteorological data sets for the 2008 high-flow season and compared with observations. The results indicate reasonable forecasting capacity (on average 17% deviation), but additional years should also be evaluated. We finish by presenting a strategy and pilot project which will develop an operational flood monitoring and forecasting system based in-situ data, earth observations, modelling, and extreme statistics. In this way we aim to build capacity to ultimately improve resilience toward floods, protecting lives and infrastructure in the region.

      PubDate: 2017-02-22T20:52:05Z
      DOI: 10.1016/j.pce.2017.02.010
       
  • Zeolite formation in the presence of cement hydrates and albite
    • Authors: Barbara Lothenbach; Ellina Bernard; Urs Mäder
      Abstract: Publication date: Available online 21 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Barbara Lothenbach, Ellina Bernard, Urs Mäder
      Zeolite formation caused by interactions between cement hydrates and rock forming minerals was investigated by two sets of batch experiments and supported by thermodynamic modelling. The first set of batch experiments investigated the interaction between calcium silicate hydrates (C-S-H) (Ca0.8SiO2.8·32H2O) and ettringite (Ca6Al2(SO4)3(OH)12(H2O)26) as cement hydrate minerals and albite (NaAlSi3O8) as a rock forming mineral at 20, 50 and 80°C. The dissolution of C-S-H, ettringite and albite led to relatively high calcium and low silicon and sodium concentrations and to the formation of zeolite P(Ca) (Ca2Al2Si2O8·4.5H2O) and natrolite (Na2Al2Si3O10·2H2O). The second set of experiments used ettringite and silica fume as cement phases and NaAlO2 to represent a rock forming mineral. High initial sodium, hydroxide and aluminium concentrations were observed leading to the precipitation of zeolite X (Na2Al2Si2.5O9·6.2H2O) and C-S-H gel at 20 and 50°C where only 40 to 60% of the silica had reacted after 3 years. At 80°C where more silica fume had reacted, the formation of SiO2-rich zeolite Y (Na2Al2Si4O12·8H2O) and chabazite (CaAl2Si4O12·6H2O) was observed. Solubility products for the zeolite P(Ca), natrolite, chabazite, zeolite X and zeolite Y were obtained from the measured concentrations. Comparison with values published in the literature shows a high variability due to the flexibility of the Si to Al ratio in zeolite structures and underlines the need for systematic experimental determination of the solubility of different zeolites.

      PubDate: 2017-02-22T20:52:05Z
      DOI: 10.1016/j.pce.2017.02.006
       
  • Evaluation of Satellite and simulated rainfall products for hydrological
           applications in the Notwane Catchment, Botswana
    • Authors: P.K. Kenabatho; B.P. Parida; D.B. Moalafhi
      Abstract: Publication date: Available online 21 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): P.K. Kenabatho, B.P. Parida, D.B. Moalafhi
      In semi-arid catchments, hydrological modelling, water resources planning and management are hampered by insufficient spatial rainfall data which is usually derived from limited rain gauge networks. Satellite products are potential candidates to augment the limited spatial rainfall data in these areas. In this paper, the utility of the Tropical Rainfall Measuring Mission (TRMM) product (3B42 v7) is evaluated using data from the Notwane catchment in Botswana. In addition, rainfall simulations obtained from a multi-site stochastic rainfall model based on the generalised linear models (GLMs) were used as additional spatial rainfall estimates. These rainfall products were compared to the observed rainfall data obtained from six (6) rainfall stations available in the catchment for the period 1998-2012. The results show that in general the two approaches produce reasonable spatial rainfall estimates. However, the TRMM products provided better spatial rainfall estimates compared to the GLM rainfall outputs on an average, as more than 90% of the monthly rainfall variations were explained by the TRMM compared to 80% from the GLMs. However, there is still uncertainty associated mainly with limited rainfall stations, and the inability of the two products to capture unusually high rainfall values in the data sets. Despite this observation, rainfall indices computed to further assess the daily rainfall products (i.e. rainfall occurrence and amounts, length of dry spells) were adequately represented by the TRMM data compared to the GLMs. Performance from the GLMs is expected to improve with addition of further rainfall predictors. A combination of these rainfall products allows for reasonable spatial rainfall estimates and temporal (short term future) rainfall simulations from the TRMM and GLMs, respectively. The results have significant implications on water resources planning and management in the catchment which has, for the past three years, been experiencing prolonged droughts as shown by the drying of Gaborone dam (currently at a record low of 1.6% full), which is the main source of water supply to the city of Gaborone and neighbouring townships in Botswana.

      PubDate: 2017-02-22T20:52:05Z
      DOI: 10.1016/j.pce.2017.02.009
       
  • Evaluation of drought using SPEI drought class transitions and log-linear
           models for different agro-ecological regions of India
    • Authors: N.M. Alam; G.C. Sharma; Elsa Moreira; C. Jana; P.K. Mishra; N.K. Sharma; D. Mandal
      Abstract: Publication date: Available online 21 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): N.M. Alam, G.C. Sharma, Elsa Moreira, C. Jana, P.K. Mishra, N.K. Sharma, D. Mandal
      Markov chain and 3-dimensional log-linear models were attempted to model drought class transitions derived from the newly developed drought index the Standardized Precipitation Evapotranspiration Index (SPEI) at a 12 month time scale for six major drought prone areas of India. Log-linear modelling approach has been used to investigate differences relative to drought class transitions for last 48 years of standardized precipitation evapotranspiration index (SPEI) data sets were divided into two periods. In this study, the probabilities of drought class transition, the mean residence time, the 1, 2 or 3 months ahead prediction of average transition time between drought classes and the drought severity class have been derived. The seasonality of precipitation has been derived for non-homogeneous Markov chains which could be used to explain the effect of the potential retreat of drought. Quasi-association and Quasi-symmetry log-linear models have been fitted to the drought class transitions derived from SPEI-12 time series. The estimates of odds along with their confidence intervals were obtained to explain the progression of drought and estimation of drought class transition probabilities. For initial months as the drought severity increases the calculated odds shows lower value and the odds decreases for the succeeding months. This indicates that the ratio of expected frequencies of occurrence of transition to the non-drought class decreases as compared to transition to any drought class when the drought severity of the present class increases. From 3-dimensional log-linear model it is clear that during the last 24 years the drought probability has increased for almost all the six regions. The findings from the present study will immensely help to assess the impact of drought on the gross primary production and to develop future contingent planning in similar region worldwide.

      PubDate: 2017-02-22T20:52:05Z
      DOI: 10.1016/j.pce.2017.02.008
       
  • Designing local solutions for emptying pit latrines in low-income urban
           settlements (Malawi)
    • Authors: W.C. Chipeta; R.H. Holm; J.F. Kamanula; W.E. Mtonga; F.L. de los Reyes
      Abstract: Publication date: Available online 21 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): W.C. Chipeta, R.H. Holm, J.F. Kamanula, W.E. Mtonga, F.L. de los Reyes
      A lack of effective options in local technology poses challenges when onsite household sanitation facilities are eventually filled to capacity in unplanned settlement areas within Mzuzu City, located in northern Malawi. Vacuum tankers currently dominate the market but focus on emptying septic tanks in the more easily accessible planned settlement areas, rather than servicing the pit latrines common in unplanned settlement areas. As a result, households in the unplanned settlement areas within Mzuzu rely primarily on manual pit emptying (i.e., shoveling by hand) or digging a new pit latrine. These practices have associated health risks and are limited by space constraints. This research focused on filling the technological gap through the design, development and testing of a pedal powered modified Gulper pump using locally available materials and fabrication. A modified pedal powered Gulper technology was developed and demonstrated to be capable of lifting fecal sludge from a depth of 1.5 m with a mean flow rate of 0.00058 m3/s. If the trash content was low, a typical pit latrine with a volume of 1 to 4 m3 could be emptied within 1 to 2 hours. Based on the findings in our research Phase IV, the pedal powered Gulper modification is promising as a potential emptying technology for pit latrines in unplanned settlement areas. The success rate of the technology is about 17% (5 out 30 sampled lined pit latrines were successful) and reflects the difficulty in finding a single technology that can work well in all types of pit latrines with varying contents. Innovative local solutions for pit emptying in low-income urban settlements of countries such as Malawi are possible when using the highest capacity fabricators available in the area. We note that cost should not be the only design criteria and acknowledge the challenge of handling trash in pit latrines.

      PubDate: 2017-02-22T20:52:05Z
      DOI: 10.1016/j.pce.2017.02.012
       
  • Modelling of cementitious backfill interactions with vitrified
           intermediate-level waste
    • Authors: Graham Baston; Timothy Heath; Fiona Hunter; Stephen Swanton
      Abstract: Publication date: Available online 21 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Graham Baston, Timothy Heath, Fiona Hunter, Stephen Swanton
      New types of wasteform are being considered for the geological disposal of radioactive intermediate-level waste (ILW) in the UK. These include vitrified ILW products arising from the application of thermal treatment processes. For disposal of such wasteforms in a geological disposal facility, a range of concepts are under consideration, including those with a high-pH cementitious backfill (the NRVB, Nirex Reference Vault Backfill). Alternatively, a cement-based material that buffers to a less alkaline pH could be used (an LPB, Low-pH Backfill). To assess the compatibility of these potential new wasteforms with cement-based disposal concepts, it is necessary to understand their impacts on the long-term evolution of the backfill. A scoping thermodynamic modelling study was undertaken to help understand the possible effects of these wasteforms on the performance of the backfill. The model primarily considers the interactions occurring between the vitirified waste, the porewater and the backfill, within a static and (in most cases) totally closed system. The approach was simplified by assuming equilibrium between the backfill and the corroded glass available at selected times, rather than involving detailed, reactive transport modelling. The aim was to provide an understanding of whether the impacts of the vitrified wastes on backfill performance are sufficient to compromise disposal in such environments. The calculations indicated that for NRVB, the overall alkaline buffering capacity of the backfill is not expected to be impaired by interactions with vitrified waste; rather the buffering will be to less alkaline pH values (above pH 9) but for a longer period. For the LPB, slightly lower pH values were predicted in some cases. The sorption capacities of the backfills are unlikely to be impaired by interactions with vitrified ILW. Indeed they may be increased, due to the additional C-S-H phase formation. The results of this study suggest that disposal of vitrified ILW in a cement-based disposal system with a high-pH backfill is a potentially viable disposal option.

      PubDate: 2017-02-22T20:52:05Z
      DOI: 10.1016/j.pce.2017.02.007
       
  • Formation of magnesium silicate hydrates (M-S-H)
    • Authors: Ellina Bernard; Barbara Lothenbach; Daniel Rentsch; Isabelle Pochard; Alexandre Dauzères
      Abstract: Publication date: Available online 21 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Ellina Bernard, Barbara Lothenbach, Daniel Rentsch, Isabelle Pochard, Alexandre Dauzères
      The formation of magnesium silicate hydrates (M-S-H) with MgO to SiO2 ratios from 0.7 to 1.6 has been studied at 20, 50 and 70°C. TGA and XRD data reveal that initially brucite and M-S-H are formed while amorphous silica is still present as indicated by FT-IR and 29Si MAS NMR experiments. In this first step M-S-H with Mg/Si ∼ 1 with pH values ∼ 9.4 is formed independently of the total Mg/Si. Investigations by FT-IR and 29Si MAS NMR detail that the structure of that initial M-S-H evolved with time and M-S-H formed with Mg/Si ranging from ∼ 0.8 to ∼ 1.3 after 2 years at 20°C and after 1 year at 50 and 70°C. This implies that the composition of synthetic M-S-H depends strongly on temperature and equilibration time. At 50 and 70°C the M-S-H formation occurs faster although it is thermodynamically slightly less stable. The solubility of M-S-H, talc and antigorite after 1 year or longer shows comparable trends.

      PubDate: 2017-02-22T20:52:05Z
      DOI: 10.1016/j.pce.2017.02.005
       
  • Evaluating the performance of the newly-launched Landsat 8 sensor in
           detecting and mapping the spatial configuration of water hyacinth
           (Eichhornia crassipes) in inland lakes, Zimbabwe
    • Authors: Timothy Dube; Onisimo Mutanga; Mbulisi Sibanda; Victor Bangamwabo; Cletah Shoko
      Abstract: Publication date: Available online 21 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Timothy Dube, Onisimo Mutanga, Mbulisi Sibanda, Victor Bangamwabo, Cletah Shoko
      The remote sensing of freshwater resources is increasingly becoming important, due to increased patterns of water use and the current or projected impacts of climate change and the rapid invasion by lethal water weeds. This study therefore sought to explore the potential of the recently-launched Landsat 8 OLI/TIRS sensor in mapping invasive species in inland lakes. Specifically, the study compares the performance of the newly-launched Landsat 8 sensor, with more advanced sensor design and image acquisition approach to the traditional Landsat-7 ETM+ in detecting and mapping the water hyacinth (Eichhornia crassipes) invasive species across Lake Chivero, in Zimbabwe. The analysis of variance test was used to identify windows of spectral separability between water hyacinth and other land cover types. The results showed that portions of the visible (B3), NIR (B4), as well as the shortwave bands (Band 8, 9 and 10) of both Landsat 8 OLI and Landsat 7 ETM, exhibited windows of separability between water hyacinth and other land cover types. It was also observed that on the use of Landsat 8 OLI produced high overall classification accuracy of 72 %, when compared Landsat 7 ETM, which yielded lower accuracy of 57 %. Water hyacinth had optimal accuracies (i.e. 92 %), when compared to other land cover types, based on Landsat 8 OLI data. However, when using Landsat 7 ETM data, classification accuracies of water hyacinth were relatively lower (i.e. 67%), when compared to other land cover types (i.e. water with accuracy of 100%). Spectral curves of the old, intermediate and the young water hyacinth in Lake Chivero based on: (a) Landsat 8 OLI, and (b) Landsat 7 ETM were derived. Overall, the findings of this study underscores the relevance of the new generation multispectral sensors in providing primary data-source required for mapping the spatial distribution, and even configuration of water weeds at lower or no cost over time and space.

      PubDate: 2017-02-22T20:52:05Z
      DOI: 10.1016/j.pce.2017.02.015
       
  • Remote sensing of surface water quality in relation to catchment condition
           in Zimbabwe
    • Authors: Mhosisi Masocha; Amon Murwira; Christopher H.D. Magadza; Rafik Hirji; Timothy Dube
      Abstract: Publication date: Available online 21 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Mhosisi Masocha, Amon Murwira, Christopher H.D. Magadza, Rafik Hirji, Timothy Dube
      The degradation of river catchments is one of the most important contemporary environmental problems affecting water quality in tropical countries. In this study, we used remotely sensed Normalised Difference Vegetation Index (NDVI) to assess how catchment condition varies within and across river catchments in Zimbabwe. We then used non-linear regression to test whether catchment condition assessed using the NDVI is significantly (α = 0.05) related with levels of Total Suspended Solids (TSS) measured at different sampling points in thirty-two sub-catchments in Zimbabwe. The results showed a consistent negative curvilinear relationship between Landsat 8 derived NDVI and TSS measured across the catchments under study. In the drier catchments of the country, 98% of the variation in TSS is explained by NDVI, while in wetter catchments, 64% of the variation in TSS is explained by NDVI. Our results suggest that NDVI derived from free and readily available multispectral Landsat series data (Landsat 8) is a potential valuable tool for the rapid assessment of physical water quality in data poor catchments. Overall, the finding of this study underscores the usefulness of readily available satellite data for near-real time monitoring of the physical water quality at river catchment scale, especially in resource-constrained areas, such as the sub-Saharan Africa.

      PubDate: 2017-02-22T20:52:05Z
      DOI: 10.1016/j.pce.2017.02.013
       
  • Interaction processes at the concrete-bentonite interface after 13 years
           of FEBEX-Plug operation. Part II: Bentonite contact
    • Authors: Raúl Fernández; Elena Torres; Ana I. Ruiz; Jaime Cuevas; María Cruz Alonso; José Luis García Calvo; Enrique Rodríguez; María Jesús Turrero
      Abstract: Publication date: Available online 20 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Raúl Fernández, Elena Torres, Ana I. Ruiz, Jaime Cuevas, María Cruz Alonso, José Luis García Calvo, Enrique Rodríguez, María Jesús Turrero
      The in situ FEBEX experiment performed at the URL in Grimsel (Swizerland) was dismantled after 18 years of operation. Interface samples between bentonite and a shotcreted concrete plug that was constructed in a second operational phase have been studied after 13 years of interaction. Mineralogical and geochemical characterization of samples have been performed by XRD, SEM-EDX, TG and FTIR techniques in addition to determinations of major ions by chemical analysis of aqueous extracts, δ18O and δ13C stable isotopes both in concrete paste and bentonite, and exchangeable cations in bentonite. Low mineralogical alteration impact was observed in bentonite that is only affected by a few millimeters. A large accumulation of Mg was observed at the bentonite side of the interface precipitating as silicates in various forms. In addition, heterogeneous carbonation was observed at the interface, but mostly affecting the concrete side. Migration of aqueous species occurred, being the most relevant the diffusion of chloride and sulfate from bentonite to concrete, in agreement with Part I of this study. Chloride advanced more into the concrete, while sulfates reacted to form ettringite, which has an evident alteration impact at the very interface (<0.5 mm rim) within the concrete. The ionic mobility has also redistributed the exchangeable cations in bentonite, increasing the content in Ca2+ and Na+, compensated by a decrease in Mg2+. The results presented in this paper complement those presented in Part I, focusing on the alteration of concrete by the bentonite and the granite groundwater.

      PubDate: 2017-02-22T20:52:05Z
      DOI: 10.1016/j.pce.2017.01.009
       
  • Simulation of the effect of an oil refining project on the water
           environment using the MIKE 21 model
    • Authors: Peng Jia; Qinggai Wang; Xuchuan Lu; Beibei Zhang; Chen Li; Sa Li; Shibei Li; Yaping Wang
      Abstract: Publication date: Available online 13 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Peng Jia, Qinggai Wang, Xuchuan Lu, Beibei Zhang, Chen Li, Sa Li, Shibei Li, Yaping Wang
      A case study of the Caofeidian oil refining project is conducted. A two-dimensional convective dispersion mathematical model is established to simulate the increase in the concentration of pollutants resulting from the wastewater discharge from the Caofeidian oil refining project and to analyze the characteristics of the dispersion of pollutants after wastewater is discharged and the effect of the wastewater discharge on the surrounding sea areas. The results demonstrate the following: (1) The Caofeidian sea area has strong tidal currents, which are significantly affected by the terrain. There are significant differences in the tidal current velocity and the direction between the deep-water areas and the shoals. The direction of the tidal currents in the deep-water areas is essentially parallel to the contour lines of the sea areas. Onshore currents and rip currents submerging the shoals are the dominant currents in the shoals. (2) The pollutant concentration field in the offshore areas changes periodically with the movement of the tidal current. The dilution and dispersion of pollutants are affected by the ocean currents in different tidal periods. The turbulent dispersion of pollutants is the most intense when a neap tide ebbs, followed by when a neap tide rises, when a spring tide ebbs and when a spring tide rises. (3) There are relatively good hydrodynamic conditions near the project's wastewater discharge outlet. Wastewater is well diluted after being discharged. Areas with high concentrations of pollutants are concentrated near the wastewater discharge outlet and the offshore areas. These pollutants migrate southwestward with the flood tidal current and northeastward with the ebb tidal current and have no significant impact on the protection targets in the open sea areas and nearby sea areas.

      PubDate: 2017-02-15T20:46:42Z
      DOI: 10.1016/j.pce.2017.02.003
       
  • Distribution and source identification of trace metals in the sediment of
           Yellow River Estuary and the adjacent Laizhou Bay
    • Authors: Yan Wang; Min Ling; Ru-hai Liu; Ping Yu; Ai-kun Tang; Xian-xiang Luo; Qimin Ma
      Abstract: Publication date: Available online 11 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Yan Wang, Min Ling, Ru-hai Liu, Ping Yu, Ai-kun Tang, Xian-xiang Luo, Qimin Ma
      Rapid economic development in the Yellow River basin has inevitably resulted in increase of pollutions in the estuary, and concern for both the environment and protection against pollutants is increasing. Contents of trace metals (Cu, Pb Zn, Cr, Cd, As, Hg), Fe, Al, total organic carbon (TOC), and their granulometry were determined in surface sediment samples from the Yellow River estuary and its adjacent areas. Metal contents were significantly correlated each other. Clay, TOC and heavy metal contents showed similar distribution characteristics, with concentrations increased from the land to the sea. The distribution of grain size plays an important role in influencing the distribution of trace metals. Heavy metal concentrations showed a significant relationship with Fe and Al content, while most heavy metals were not enriched. These results were also confirmed by the analysis of enrichment factors and principal component analysis of the metals. The metal content of the Yellow River Estuary sediments was similar to the content observed 20 years ago, but the concentrations of most metals in Laizhou Bay decreased. The decrease in the carrying sediment of the Yellow River might be responsible for this pattern.

      PubDate: 2017-02-15T20:46:42Z
      DOI: 10.1016/j.pce.2017.02.002
       
  • Reactive transport models of a high–pH infiltration test in concrete
    • Authors: M. Carme Chaparro; Josep M. Soler; Maarten W. Saaltink; Urs K. Mäder
      Abstract: Publication date: Available online 4 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): M. Carme Chaparro, Josep M. Soler, Maarten W. Saaltink, Urs K. Mäder
      A laboratory-scale tracer test was carried out to characterize the transport properties of concrete from the Radioactive Waste Disposal Facility at El Cabril (Spain). A hyperalkaline solution (K-Ca-OH, pH = 13.2) was injected into a concrete sample under a high entry pressure in order to perform the experiment within a reasonable time span, obtaining a decrease of permeability by a factor of 1000. The concentrations of the tracers, major elements (Ca2+, SO4 2−, K+ and Na+) and pH were measured at the outlet of the concrete sample. A reactive transport model was built based on a double porosity conceptual model, which considers diffusion between a mobile zone, where water can flow, and an immobile zone without any advective transport. The numerical model assumed that all reactions took place in the immobile zone. The cement paste consists of C-S-H gel, portlandite, ettringite, calcite and gypsum, together with residual alite and belite. Two different models were compared, one with portlandite in equilibrium (high initial surface area) and another one with portlandite reaction controlled by kinetics (low initial surface area). Overall the results show dissolution of alite, belite, gypsum and quartz and precipitation of C-S-H gel, portlandite, ettringite and calcite. Permeability could have decreased due to mineral precipitation.

      PubDate: 2017-02-09T20:42:20Z
      DOI: 10.1016/j.pce.2017.01.010
       
  • Use of Landsat series data to analyse the spatial and temporal variations
           of land degradation in a dispersive soil environment: A case of King
           Sabata Dalindyebo local municipality in the Eastern Cape Province, South
           Africa
    • Authors: Timothy Dube; Onisimo Mutanga; Mbulisi Sibanda; Khoboso Seutloali; Cletah Shoko
      Abstract: Publication date: Available online 4 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Timothy Dube, Onisimo Mutanga, Mbulisi Sibanda, Khoboso Seutloali, Cletah Shoko
      Land degradation as a result of inappropriate land use practices, such as overgrazing and cultivation on steep slopes, etc. is one of the major global environmental challenges. Specifically, land degradation threatens the productivity and sustainability of the natural environment, agriculture, and most importantly rural economies in most developing countries, particularly the sub-Saharan region. The main aim of this study was therefore, to assess the potential and strength of using the free or readily available Landsat series data in mapping degraded land areas at the King Sabata Dalindyebo local municipality in the Eastern Cape, South Africa (1984–2010). Data analysis was done using a robust non-parametric classification ensemble; Discriminant Analysis (DA). The results show that degraded areas vary over the years. For example, the results show that the year 1994 and 2004 incurred high degradation levels, when compared to the year 1984 and 2010. Moreover, the observed degradation significantly (α = 0.05) varies with soil type. The chromic acrisols have the highest levels of erosion (approx. 80% in 1984), when compared to humic-umbric acrisols (less than 10% for the entire period under study). It can also be observed that considerable part of degradation occurred in the northern part of the municipal district. Overall, the findings of this research underlines the importance and efficacy of multispectral Landsat series data-set in mapping and monitoring levels of land degradation in data-scarce catchments.

      PubDate: 2017-02-09T20:42:20Z
      DOI: 10.1016/j.pce.2017.01.023
       
  • Potential application of synthesized ferrocenylimines compounds for the
           elimination of bacteria in water
    • Authors: M.I. Ikhile; T.G. Barnard; J.C. Ngila
      Abstract: Publication date: Available online 4 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): M.I. Ikhile, T.G. Barnard, J.C. Ngila
      This work reports a study towards a search for environmentally friendly water disinfectant. The most common method for water treatment is based on chlorine which had a wide application over the years as a water disinfectant, but suffer the disadvantage of reacting with natural organic matter to form disinfection by products. In this study, the potential application of novel ferrocenylimines compounds, namely 4-ferrocenylaniline (1), N-(3-bromo-2-hydroxylbenzylidene)-4-ferrocenylimine (2) and N-(3-bromo-5-chlorosalicyl)-4-ferrocenylimine (3) for the elimination of bacteria in water was investigated by evaluating their antibacterial properties against twelve different bacterial strains using microdilution method in sterile 96 well micro titer plates. The in vitro antibacterial activity revealed that the ferrocenylimines compound exhibit higher antibacterial activity than ferrocene, which is one of the starting materials towards the synthesis of this novel ferrocenylimines compounds. The most active ferrocenylimines compound was compound 3 with a minimal inhibitory concentration (MIC) value of 0.30 mg/ml against S. sonnei. In addition, all the ferrocenylimines compounds possessed excellent antibacterial activity against B. cereus with the same MIC value of 0.31 mg/ml. The results obtained so far show great potential in the three tested ferrocenylimines compounds for use in water treatment in killing bacteria in water.

      PubDate: 2017-02-09T20:42:20Z
      DOI: 10.1016/j.pce.2017.01.022
       
  • Denitrification of soil nitrogen in coastal and inland salt marshes with
           different flooding frequencies
    • Authors: Junhong Bai; Xin Wang; Jia Jia; Guangliang Zhang; Wei Wang; Shuai Zhang
      Abstract: Publication date: Available online 3 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Junhong Bai, Xin Wang, Jia Jia, Guangliang Zhang, Wei Wang, Shuai Zhang
      Denitrification is an important process for removing nitrogen in wetlands, and it is influenced by many environmental factors. However, little information is available on the relationship between hydrologic conditions and denitrification. In this study three typical sampling sites with different flooding frequencies, including short-term flooding wetlands (STFW), seasonal-flooding wetlands (SFW) and tidal flooding wetlands (TFW) were chosen as the study sites in the Yellow River Delta. In contrast, five typical sampling sites with different flooding frequencies, including 100-year floodplain (H), 10-year floodplain (T), 5-year floodplain (F), 1-year floodplain (O) and permanently flooded floodplain (B) were chosen as the study sites in Xianghai wetlands. This study reflected that the denitrification rates decreased with depth along soil profiles in both inland and coastal salt marsh soils. Flooding periods, soil depth and their interaction showed significant effects on the denitrification processes. Generally, higher flooding frequencies will cause higher denitrification rates in salt marshes. Moreover, the denitrification rates were significantly positively correlated with soil moisture content in both wetlands. Additionally, the denitrification rates were significantly positively correlated with organic matter and NO3 -_N content while negatively correlated with soil pH and salinity in inland salt marshes. Therefore, the changes in soil properties (e.g. SOM, TN, pH and salinity) can become an important way to control NO3 - levels in inland salt marshes.

      PubDate: 2017-02-03T20:37:49Z
      DOI: 10.1016/j.pce.2017.01.015
       
  • Effect of incorporating graphene oxide and surface imprinting on
           polysulfone membranes on flux, hydrophilicity and rejection of salt and
           polycyclic aromatic hydrocarbons from water
    • Authors: Rose Waithiegeni Kibechu; Derek Dinteh; Titus Alfred Makudali Msagati; Bhekie Briliance Mamba
      Abstract: Publication date: Available online 3 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Rose Waithiegeni Kibechu, Derek Dinteh, Titus Alfred Makudali Msagati, Bhekie Briliance Mamba
      We report a significant enhancement of hydrophillity of polysulfone (Psf) membranes after modification with graphene oxide (GO) as a filler followed by surface imprinting on the surface of GO/Psf composite imprinted membranes (CIMs). The surface imprinting on the GO-Psf membrane was employed in order to enhance its selectivity towards polycyclic aromatic hydrocarbons (PAHs) in water. The CIMs were prepared through a process of phase inversion of a mixture of graphene oxide and polysulfone (Psf) in N-methylpyrrolidone (NMP). Fourier-transform spectroscopy (FT-IR) of the imprinted showed new peaks at 935 cm−1 and 1638 cm−1 indicating success in surface imprinting on the GO-Psf membrane. The CIM also showed improvement in flux from 8.56 LM−2 h−1 of unmodified polysulfone membrane to 15.3 LM−2 h−1 in the CIM, salt rejection increased from 57.2 ± 4.2% of polysulfone membrane to 76 ± 4.5%. The results obtained from the contact angle measurements showed a decrease with increase in GO content from 72 ± 2.7% of neat polysulfone membrane to 62.3 ± 2.1% of CIM indicating an improvement in surface hydrophilicity. The results from this study shows that, it is possible to improve the hydrophilicity of the membranes without affecting the performance of the membranes.

      PubDate: 2017-02-03T20:37:49Z
      DOI: 10.1016/j.pce.2017.01.021
       
  • Scenario simulation of land exploitation and risk assessment of soil
           erosion in the low-slope hilly area of the Erhai basin
    • Authors: Gui Jin; Xiangzheng Deng; Yongwei Yuan; Sai Ma; Zhaohua Li; Saiya Shi
      Abstract: Publication date: Available online 3 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Gui Jin, Xiangzheng Deng, Yongwei Yuan, Sai Ma, Zhaohua Li, Saiya Shi
      Risk assessment of soil erosion is an important prerequisite to develop the low-slope hilly in basin-scale. Using Dynamics of Land System model (DLS), we design the scenario simulation of land exploitation of Dali city which is located in the Erhai basin and typical as low-slope hilly area. Then we bring in Universal Soil Loss Equation (USLE) to assess the risks of soil erosion under different scenarios. In two simulating scenarios, baseline scenario and planning scenario respectively, the spatial distribution pattern of land use of the study area in 2020 shows an overall consistency and a partial difference. The cultivated resources of Dali has been protected since the cultivated land located in dam area has not changed, while construction land has expanded more or less on the basis of existing built-up areas. Specifically, the expansion of construction land in planning scenario is concentrated on Haidong town and Fengyi town where there are rich in low-slope hilly resources. In two scenarios mentioned above, both the value-at-risk of soil erosion and its risk level have no significant rise or drop from 2008 to 2020. As the risk index of soil erosion in baseline scenario is 0.003 taller than in planning scenario, one conclusion can be drawn that the planning scenario will lower the overall risk of soil erosion and should be used to develop gentle hillside area in Erhai basin. The risk evaluation of soil erosion under different scenarios is valuable for land management decisions because the results provide fundamental information for optimal utilization of land use and prevention of ecological risks in the low-slope hilly regions.

      PubDate: 2017-02-03T20:37:49Z
      DOI: 10.1016/j.pce.2017.01.020
       
  • Estimating groundwater levels using system identification models in
           Nzhelele and Luvuvhu areas, Limpopo Province, South Africa
    • Authors: Rachel Makungo; John O. Odiyo
      Abstract: Publication date: Available online 3 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Rachel Makungo, John O. Odiyo
      This study was focused on testing the ability of a coupled linear and non-linear system identification model in estimating groundwater levels. System identification provides an alternative approach for estimating groundwater levels in areas that lack data required by physically-based models. It also overcomes the limitations of physically-based models due to approximations, assumptions and simplifications. Daily groundwater levels for 4 boreholes, rainfall and evaporation data covering the period 2005–2014 were used in the study. Seventy and thirty percent of the data were used to calibrate and validate the model, respectively. Correlation coefficient (R), coefficient of determination (R2), root mean square error (RMSE), percent bias (PBIAS), Nash Sutcliffe coefficient of efficiency (NSE) and graphical fits were used to evaluate the model performance. Values for R, R2, RMSE, PBIAS and NSE ranged from 0.8 to 0.99, 0.63 to 0.99, 0.01–2.06 m, −7.18 to 1.16 and 0.68 to 0.99, respectively. Comparisons of observed and simulated groundwater levels for calibration and validation runs showed close agreements. The model performance mostly varied from satisfactory, good, very good and excellent. Thus, the model is able to estimate groundwater levels. The calibrated models can reasonably capture description between input and output variables and can, thus be used to estimate long term groundwater levels.

      PubDate: 2017-02-03T20:37:49Z
      DOI: 10.1016/j.pce.2017.01.019
       
  • Effect of coastal eutrophication on growth and physiology of Spartina
           alterniflora Loisel
    • Authors: Yu Zhang; Baoshan Cui; Tian Xie; Qing Wang; Jiaguo Yan
      Abstract: Publication date: Available online 3 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Yu Zhang, Baoshan Cui, Tian Xie, Qing Wang, Jiaguo Yan
      Coastal eutrophication has become a driver of coastal wetlands loss. Eutrophication caused by the increase of nitrogen content was one of the most main reasons. We analyzed that exogenous ammonium nitrogen (EAN) of different concentration influenced on the growth and physiology of Spartina alterniflora Loisel (S. alterniflora) through simulated conditions. The results showed that growth of the root system largely depended on the environment conditions around S. alterniflora. Higher nitrogen concentration promoted aboveground biomass and increased plant height. On the other hand, as the increase of growth period, higher nitrogen concentration could inhibit the elongation growth of root and reduce the underground biomass. We showed that activity of POD, SOD and MDA content changed in an upward trend along with the increased nitrogen level. There was a significant positive correlation between H+ flux and NO3 - flux (r = 0.601, P < 0.01), and a significant negative correlation between H+ flux and NH4 + flux (r = –0.713, P < 0.01) within 1.5 mm from the root tip of S. alterniflora. Efflux and influx of ions were associated with changes of nitrogen levels. This research will provide data supporting for coastal wetland restoration of biodiversity reduction caused by coastal eutrophication.

      PubDate: 2017-02-03T20:37:49Z
      DOI: 10.1016/j.pce.2017.01.016
       
  • Land-use-change induced dynamics of carbon stocks of the terrestrial
           ecosystem in Pakistan
    • Authors: Dongdong Chen; Xiangzheng Deng; Gui Jin; Abdus Samie; Zhaohua Li
      Abstract: Publication date: Available online 3 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Dongdong Chen, Xiangzheng Deng, Gui Jin, Abdus Samie, Zhaohua Li
      In recent years, dramatic decline of ecosystem service due to large scale human induced land use change activities, which has received much attention of researchers as diminishing of ecosystem function affects the sustainability of human society, economy and environmental protection. The study aims to analyze the impact of land use change on ecosystem service of carbon sequestration in Pakistan. This study, based on Dynamics of Land System (DLS) model, simulating the future land use changes, combing with Integrated Valuation of Environmental Services and Trade-offs (InVEST) model, has analyzed the changes in quantity and distribution of carbon stock in Pakistan under alternative land use scenarios for 2020 using historical land use data from 2006 to 2009. The results indicate that comparing the carbon stocks in 2009, only the Business-as-usual scenario of carbon stocks continue to decrease; the other two scenarios of carbon stocks show the increasing trend. Moreover, the Ecological protection scenario has the highest carbon storage, but it is not feasible to the current conditions of Pakistan, whereas Investment priority oriented scenario could be ideal one. The advances in research underpin scientific efforts to connect dynamic land use change with ecosystem service of carbon storage in Pakistan.

      PubDate: 2017-02-03T20:37:49Z
      DOI: 10.1016/j.pce.2017.01.018
       
  • Traditional Portland cement and MgO-based cement: a promising
           combination?
    • Authors: Monica Tonelli; Francesca Martini; Lucia Calucci; Marco Geppi; Silvia Borsacchi; Francesca Ridi
      Abstract: Publication date: Available online 2 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Monica Tonelli, Francesca Martini, Lucia Calucci, Marco Geppi, Silvia Borsacchi, Francesca Ridi
      MgO/SiO2 cements are materials potentially very useful for radioactive waste disposal, but knowledge about their physico-chemical properties is still lacking. In this paper we investigated the hydration kinetics of cementitious formulations prepared by mixing MgO/SiO2 and Portland cement in different proportions and the structural properties of the hydrated phases formed in the first month of hydration. In particular, the hydration kinetics was investigated by measuring the free water index on pastes by means of differential scanning calorimetry, while the structural characterization was carried out by combining thermal (DTA), diffractometric (XRD), and spectroscopic (FT-IR, 29Si solid state NMR) techniques. It was found that calcium silicate hydrate (C-S-H) and magnesium silicate hydrate (M-S-H) gels mainly form as separate phases, their relative amount and structural characteristics depending on the composition of the hydrated mixture. Moreover, the composition of the mixtures strongly affects the kinetics of hydration and the pH of the aqueous phase in contact with the cementitious materials. The results here reported show that suitable mixtures of Portland cement and MgO/SiO2 could be used to modify the properties of hydrated phases with potential application in the storage of nuclear waste in clayey disposal.

      PubDate: 2017-02-03T20:37:49Z
      DOI: 10.1016/j.pce.2017.01.011
       
  • Effect of particulate air pollution on coronary heart disease in China:
           Evidence from threshold GAM and Bayesian hierarchical model
    • Authors: Xiaoyu Chen
      Abstract: Publication date: Available online 2 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Xiaoyu Chen
      There are few multicity studies to address the effect of short-term effect of particulate matter air pollution on daily Coronary Heart Disease (CHD) mortality in developing countries, much fewer to further discuss its threshold and seasonal effect. This study investigates the season-varying association between particulate matter less than or equal to 10 μm in aerodynamic diameter (PM10) and daily CHD mortality in seven cities of China. Time series threshold Poisson regression model is specified to estimate the health effect for four cities with the threshold effect, and conventional linear Poisson model is used to analyze the effect for three cities without threshold. We apply the Bayesian hierarchical model to pool the city-specific estimates into overall level. On average, a 10 μg/m3 increase of the moving average concentrations of current-day and previous-day PM10 is associated with an increase of 0.81% (95% Posterior Interval, PI: −0.04%, 1.67%) in daily CHD mortality for all the cities as a whole. The associations are smaller than reported in developed countries or regions with lower polluted level, which is consistent to the findings in the literature. The hazardous effect are higher in hot summer and cold winter (1.15% and 0.89%) but lower in relative warm spring and fall (0.85% and 0.69%). In summary, we found significant associations between short-term exposure to PM10 and CHD mortality in China. The sensitivity analyses in the study support the robustness of our results.

      PubDate: 2017-02-03T20:37:49Z
      DOI: 10.1016/j.pce.2017.01.013
       
  • Understanding land use change impacts on microclimate using Weather
           Research and Forecasting (WRF) Model
    • Authors: Xia Li; Chandana Mitra; Li Dong; Qichun Yang
      Abstract: Publication date: Available online 2 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Xia Li, Chandana Mitra, Li Dong, Qichun Yang
      To explore potential climatic consequences of land cover change in the Kolkata Metropolitan Development area, we projected microclimate conditions in this area using the Weather Research and Forecasting (WRF) Model driven by future land use scenarios. Specifically, we considered two land conversion scenarios including an urbanization scenario that all the wetlands and croplands would be converted to built-up areas, and an irrigation expansion scenario in which all wetlands and dry croplands would be replaced by irrigated croplands. Results indicated that land use and land cover (LULC) change would dramatically increase regional temperature in this area under the urbanization scenario, but expanded irrigation tended to have a cooling effect. In the urbanization scenario, precipitation center tended to move eastward and lead to increased rainfall in eastern parts of this region. Increased irrigation stimulated rainfall in central and eastern areas but reduced rainfall in southwestern and northwestern parts of the study area. This study also demonstrated that urbanization significantly reduced latent heat fluxes and albedo of land surface; while increased sensible heat flux changes following urbanization suggested that developed land surfaces mainly acted as heat sources. In this study, climate change projection not only predicts future spatiotemporal patterns of multiple climate factors, but also provides valuable insights into policy making related to land use management, water resource management, and agriculture management to adapt and mitigate future climate changes in this populous region.

      PubDate: 2017-02-03T20:37:49Z
      DOI: 10.1016/j.pce.2017.01.017
       
  • Salinity-driven shifts in the activity, diversity, and abundance of
           anammox bacteria of estuarine and coastal wetlands
    • Authors: Xiaofen Jiang; Lijun Hou; Yanling Zheng; Min Liu; Guoyu Yin; Juan Gao; Xiaofei Li; Rong Wang; Chendi Yu; Xianbiao Lin
      Abstract: Publication date: Available online 2 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Xiaofen Jiang, Lijun Hou, Yanling Zheng, Min Liu, Guoyu Yin, Juan Gao, Xiaofei Li, Rong Wang, Chendi Yu, Xianbiao Lin
      Anaerobic ammonium oxidation (anammox) plays a significant role in nitrogen removal in estuarine and coastal wetlands. However, the effects of changing salinity on anammox activity and anammox bacterial dynamics in these environments are not well understood. In this study, serial incubation experiments with a salinity gradient (0-40) were conducted to explore the responses of anammox bacterial activity, diversity and abundance to the changing salinity in the intertidal wetland of the Yangtze Estuary. Results show that activity and abundance of anammox bacteria firstly increased with the increase of salinity, but they were physiologically stressed by high-level salinity (>30) in a short-term incubation (<10 days). However, the treatment with salinity of 5 showed the maximal anammox activity and anammox bacterial abundance after a long-term incubation (60-120 days). In addition, Kuenenia (Kuenenia stuttgartiensis), Scalindua (Scalindua wagner, marina, and brodae), and three unknown anammox-like groups were observed, and anammox bacterial diversity increased along the salinity gradient. Anammox community structure varied slightly within the first 10-day incubation, but the dominant anammox bacterial group shifted from Kuenenia to Scalindua with increasing salinity after the long-term incubation. Overall, this study demonstrates the effects of salinity on anammox bacterial community and anammox activity, and suggests the importance of salinity in regulating the anammox process in estuarine and coastal wetlands with frequent salinity fluctuation.

      PubDate: 2017-02-03T20:37:49Z
      DOI: 10.1016/j.pce.2017.01.012
       
  • Impact assessments of water allocation on water environment of river
           network: Method and application
    • Authors: Qinggai Wang; Yaping Wang; Xuchuan Lu; Peng Jia; Beibei Zhang; Chen Li; Sa Li; Shibei Li
      Abstract: Publication date: Available online 2 February 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Qinggai Wang, Yaping Wang, Xuchuan Lu, Peng Jia, Beibei Zhang, Chen Li, Sa Li, Shibei Li
      Two types of water allocation senarioes were proposed for reasonably utilizing water resources and improving water quality in a two-river network in Tongzhou District. Water circulation and quality were selected as two important indexes to evaluate the two senarioe. Meanwhile, one-dimensional water amount and quality model was set up on the basis of the MIKE11 model to compare the two senarioes in terms of improving water environment. The results showed that both senarioes changed the hydrodynamic conditions, and consequently the river flow reached 0.05 m/s or higher in the central part of river stream. In addition, we also found that the two plans have similar effects on water quality, with first senarioe producing larger area of water class III and IV than the second senarioe.

      PubDate: 2017-02-03T20:37:49Z
      DOI: 10.1016/j.pce.2017.01.014
       
  • Articulating the history and major departure points evident in
           post-apartheid South African national water policy and law
    • Authors: C. Chikozho; L. Danga; D. Saruchera
      Abstract: Publication date: Available online 28 January 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): C. Chikozho, L. Danga, D. Saruchera
      Governance of the water sector in South Africa has reflected the political changes taking place in society. For instance, due to apartheid policies of segregation, inequality of access to water resources marks South Africa's history in a very profound way and redistribution of rights to water to redress the results of past discrimination became an explicit purpose of the post-apartheid water governance policy and legislative regime. In this paper, we articulate the history and major departure points evident in post-apartheid South African national water policy and law. This includes documenting and reflecting on most of the available information that shows how the new water policy and law were developed. Findings from the study show that the key players active in the water law review process deliberately took into account the political goals and dynamics of power asymmetry within which the law was being articulated. Therefore, the water law as it stands today and in the past must be understood within the context of the socio-economic and political landscape that has prevailed in South Africa at different historical junctures. We contend that a detailed examination and articulation of the history and major departure points evident in post-apartheid South African national water policy and law enables practitioners and scholars to better understand the main motivations behind the water sector reforms and the then prevailing thinking behind the policy and legislation eventually promulgated. The present water law must be understood in the context of these reforms and the objectives they sought to achieve.

      PubDate: 2017-02-03T20:37:49Z
      DOI: 10.1016/j.pce.2017.01.006
       
  • Site - building resonance response in a complex geological setting: Ground
           motions recorded in the centre of Paleohora Basin and at a rock fractured
           outcrop site close to the basin edge (SW Crete, Greece)
    • Authors: Margarita Moisidi
      Abstract: Publication date: Available online 27 January 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Margarita Moisidi
      Seismic site characterization is an important parameter in earthquake hazard assessment for risk mitigation studies, which are essential in engineering design practices and urban planning providing useful information to governmental or private civil protection authorities. Recent advances from site effect studies envisage for the future the importance of incorporating microzonation as a tool for determining resonance prone buildings especially for the most earthquake hazardous municipalities. This study aims to assess the frequencies of vibration of selected masonry and reinforced concrete buildings and to examine potential soil - building resonance in a complex geological setting of the small scale Paleohora Basin (southwest Crete). Ambient noise survey was performed in masonry and reinforced concrete buildings, on soil foundation and on soil at several distances from the base of the selected buildings. The selected public and private (masonry and RC) building constructions are located in the centre of the Basin which is characterized by heterogeneities induced by large scale E-W fault and at rock fractured (of complex orientation and opening of fractures and joints) outcrop site close to the margins of the Basin in the southeast bordered by an NNE-SSW fault. The spatial horizontal to vertical spectral ratio (HVSR) technique using ambient noise reveals that soil-building resonance phenomena could be inferred in the small scale alluvial Paleohora Basin. Two amplified peaks in the centre of the Basin and one amplified peak at the rock fractured outcrop site close to the Basin margins are observed from the data sets. In the centre of the Basin, the amplified peak at medium frequency (3.85–7.11 Hz) is related to the near subsurface irregularities locally induced by E-W faulting, while the low frequency (0.75 Hz) is related to the overlain Quaternary deposits. At the rock fractured outcrop site close to the margins of the Basin the one amplified peak at medium frequencies (2.5 Hz) is related to the fractured limestone outcrop. Weak motion earthquake data following the main earthquake event that occurred near to the southwest coast of Paleohora are recorded in the centre of the Basin (at the schoolyard) and on rock fractured outcrop close to the margins of the Basin. The HVSR of the weak motion earthquake data present in the center of the Basin two amplified peaks at low (0.75 Hz) and medium frequencies (6.56 Hz) and at the rock fractured outcrop site close to the Basin edge one amplified peak at medium frequencies (2.58 Hz). This study conducted in the complex small scale and dense populated Basin, highlights the necessity of incorporating the determination of prone resonance buildings into urban planning for risk mitigation studies, specifically in this earthquake hazardous municipality.

      PubDate: 2017-01-27T19:58:10Z
      DOI: 10.1016/j.pce.2017.01.007
       
  • Detecting CO2 anomalies in a spring on Mt. Amiata volcano (Italy)
    • Authors: L. Pierotti; F. Gherardi; G. Facca; L. Piccardi; G. Moratti
      Abstract: Publication date: Available online 27 January 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): L. Pierotti, F. Gherardi, G. Facca, L. Piccardi, G. Moratti
      Located at the south-western slope of the Mt. Amiata volcano (Tuscany, Central Italy), the Bagnore spring has been investigated for geochemical precursors of earthquakes from 2004 to 2015. Over this period, several parameters of the spring have been monitored by discrete and continuous sampling. An automatic continuous monitoring station, equipped with sensors for the measurement of temperature, pH, redox potential, electrical conductivity, CO2 and CH4 dissolved concentration, is transmitting the registered signals to the remote server in Pisa 150 km northwest of Mt. Amiata. The Bagnore spring drains a shallow, short-circuiting aquifer hosted in the volcanic rocks of the volcano. Its emergence point is located in proximity of the intersection of two major fault systems that are supposed to provide a preferential ascent path to hydrothermal gases, mainly represented by C O 2 ( g ) and H 2 S ( g ) , locally rising from depth. The most evident change occurred in the registered signals over the period is represented by the sudden increase in CO2 concentration measured starting from April 2010. Along with this increase in CO2, a slight increase in water temperature and in S O 4 concentration, associated to a decrease in pH, was also recorded. This trend has been interpreted as an evidence for the augmented inflow of deep gases into the shallow aquifer. The CO2 continuous signal recorded by the Bagnore automatic station has been then processed by applying multiple statistical techniques (i.e. artificial neural network analysis and Census I method) in the search for anomalies possibly related to local seismic activity. Anomalous signals have been detected starting from April 24, 2010, and the correlation with the most energetic seismic events has been tentatively proposed.

      PubDate: 2017-01-27T19:58:10Z
      DOI: 10.1016/j.pce.2017.01.008
       
  • In situ interactions between Opalinus Clay and Low Alkali Concrete
    • Authors: Catherine Lerouge; Stéphane Gaboreau; Sylvain Grangeon; Francis Claret; Fabienne Warmont; Andreas Jenni; Veerle Cloet; Urs Mäder
      Abstract: Publication date: Available online 18 January 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Catherine Lerouge, Stéphane Gaboreau, Sylvain Grangeon, Francis Claret, Fabienne Warmont, Andreas Jenni, Veerle Cloet, Urs Mäder
      A five-year-old interface between a Low Alkali Concrete (LAC) formulation (CEM III/B containing 66% slag and 10% nano-silica) and Opalinus Clay (OPA) from a field experiment at Mont Terri Underground Rock Laboratory in Switzerland (Jenni et al., 2014) has been studied to decipher the textural, mineralogical and chemical changes that occurred between the two reacting materials. Reactivity between LAC concrete and OPA is found to be limited to a ∼1mm thick highly porous (ca. 75% porosity) white crust developed on the concrete side. Quantitative mineralogical mapping of the white crust using an electron microprobe and infrared spectroscopy on the cement matrix provides evidence of a Mg-rich phase accounting for approximatively 25 weight % of the matrix associated with 11 weight % of calcite, calcium silicate hydrate (C-S-H) and other cement phases. EDX analyses and electron diffraction combined with transmission electron microscopy of the Mg-rich phase provide evidence for a tri-octahedral 2:1 phyllosilicate with mean composition: (Ca0.5±0.2) (Mg2.0±0.4, Fe0.2±0.1, Al0.5±03, □0.3±0.3) (Al0.9±0.2, Si3.1±0.2) O10 (OH)2, where □ represents vacancies in the octahedral site Apart from this reactive contact, textural, mineralogical and chemical modifications at the contact with the LAC concrete are limited. OPA mineralogy remains largely unmodified. X-ray micro-fluorescence and EPMA mapping of major elements on the OPA side also provides evidence for a Mg-enriched 300 to 400μm thick layer. The cation exchange capacity (CEC) values measured in the OPA in contact with the LAC concrete range between 153 and 175 meq kg−1 of dry OPA, close to the reference value of 170 ± 10 meq kg−1 of dry OPA (Pearson et al., 2003). Changing cation occupancies at the interface with LAC concrete are mainly marked by increased Ca, Mg and K, and decreased Na. Leaching tests performed on OPA with deionized water and at different solid to water ratios strongly suggest that Cl and SO4 have either conservative behaviour or are constrained by the solubility of a precipitated sulfate phase. The Cl and SO4 concentrations measured at 2 cm from the interface are close to concentrations of undisturbed OPA pore waters (SO4: 4.5 ± 1.5 mmol kg−1 of dry OPA; Cl: 7.5 ± 2.1 mmol kg−1of dry OPA), and increase towards the interface with the concrete. The SO4 to Cl ratio also increases towards the interface, suggesting that the increasing anion concentrations are not related to porosity variations but rather to a concentration gradient and sulfate phase precipitation near the interface.

      PubDate: 2017-01-21T19:21:49Z
      DOI: 10.1016/j.pce.2017.01.005
       
  • Interaction of ordinary Portland cement and Opalinus Clay: dual porosity
           modelling compared to experimental data
    • Authors: A. Jenni; T. Gimmi; P. Alt-Epping; U. Mäder; V. Cloet
      Abstract: Publication date: Available online 18 January 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): A. Jenni, T. Gimmi, P. Alt-Epping, U. Mäder, V. Cloet
      Interactions between concrete and clays are driven by the strong chemical gradients in pore water and involve mineral reactions in both materials. In the context of a radioactive waste repository, these reactions may influence safety-relevant clay properties such as swelling pressure, permeability or radionuclide retention. Interfaces between ordinary Portland cement and Opalinus Clay show weaker, but more extensive chemical disturbance compared to a contact between low-pH cement and Opalinus Clay. As a consequence of chemical reactions porosity changes occur at cement-clay interfaces. These changes are stronger and may lead to complete pore clogging in the case of low-pH cements. The prediction of pore clogging by reactive transport simulations is very sensitive to the magnitude of diffusive solute fluxes, cement clinker chemistry, and phase reaction kinetics. For instance, the consideration of anion-depleted porosity in clays substantially influences overall diffusion and pore clogging at interfaces. A new concept of dual porosity modelling approximating Donnan equilibrium is developed and applied to an ordinary Portland cement – Opalinus Clay interface. The model predictions are compared with data from the cement-clay interaction (CI) field experiment in the Mt Terri underground rock laboratory (Switzerland), which represent 5 y of interaction. The main observations such as the decalcification of the cement at the interface, the Mg enrichment in the clay detached from the interface, and the S enrichment in the cement detached from the interface, are qualitatively predicted by the new model approach. The model results reveal multiple coupled processes that create the observed features. The quantitative agreement of modelled and measured data can be improved if uncertainties of key input parameters (tortuosities, reaction kinetics, especially of clay minerals) can be reduced.

      PubDate: 2017-01-21T19:21:49Z
      DOI: 10.1016/j.pce.2017.01.004
       
  • Carbon nanotube embedded PVDF membranes: Effect of solvent composition on
           the structural morphology for membrane distillation
    • Authors: Edgar C. Mapunda; Bhekie B. Mamba; Titus A.M. Msagati
      Abstract: Publication date: Available online 12 January 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Edgar C. Mapunda, Bhekie B. Mamba, Titus A.M. Msagati
      Rapid population increase, growth in industrial and agricultural sectors and global climate change have added significant pressure on conventional freshwater resources. Tapping freshwater from non-conventional water sources such as desalination and waste water recycling is considered as sustainable alternative to the fundamental challenges of water scarcity. However, affordable and sustainable technologies need to be applied for the communities to benefit from the treatment of non-conventional water source. Membrane distillation is a potential desalination technology which can be used sustainably for this purpose. In this work multi-walled carbon nanotube embedded polyvinylidene fluoride membranes for application in membrane distillation desalination were prepared via non-solvent induced phase separation method. The casting solution was prepared using mixed solvents (N, N-dimethylacetamide and triethyl phosphate) at varying ratios to study the effect of solvent composition on membrane morphological structures. Membrane morphological features were studied using a number of techniques including scanning electron microscope, atomic force microscope, SAXSpace tensile strength analysis and membrane thickness, porosity and contact angle measurements. It was revealed that membrane hydrophobicity, thickness, tensile strength and surface roughness were increasing as the composition of N, N-dimethylacetamide in the solvent was increasing with maximum values obtained between 40 – 60 % N, N-dimethylacetamide. Internal morphological structures were changing from cellular structures to short finger-like and sponge-like pores and finally to large macro void type of pores when the amount of N, N-dimethylacetamide in the solvent was changed from low to high respectively. Multi-walled carbon nanotube embedded polyvinylidene fluoride membranes of desired morphological structures and physical properties can be synthesized by regulating the composition of solvents used to prepare the casting solution.

      PubDate: 2017-01-13T18:19:22Z
      DOI: 10.1016/j.pce.2017.01.003
       
  • The potential vulnerability of the Namib and Nama Aquifers due to low
           recharge levels in the area surrounding the Naukluft Mountains, SW Namibia
           
    • Authors: Winnie N. Kambinda; Benjamin Mapani
      Abstract: Publication date: Available online 11 January 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Winnie N. Kambinda, Benjamin Mapani
      The Naukluft Mountains in the Namib Desert are a high rainfall-high discharge area. It sees increased stream-, spring- flow as well as waterfalls during the rainy season. The mountains are a major resource for additional recharge to the Namib and Nama aquifers that are adjacent to the mountains. This paper aimed to highlight the potential vulnerability of the aquifers that surround the Naukluft Mountain area; if the strategic importance of the Naukluft Karst Aquifer (NKA) for bulk water supply becomes necessary. Chloride Mass Balance Method (CMBM) was applied to estimate rainfall available for recharge as well as actual recharge thereof. This was applied using chloride concentration in precipitation, borehole and spring samples collected from the study area. Groundwater flow patterns were mapped from hydraulic head values. A 2D digital elevation model was developed using Arc-GIS. Results highlighted the influence of the NKA on regional groundwater flow. This paper found that groundwater flow was controlled by structural dip and elevation. Groundwater was observed to flow predominantly from the NKA to the south west towards the Namib Aquifer in two distinct flow patterns that separate at the centre of the NKA. A distinct groundwater divide was defined between the two flow patterns. A minor flow pattern from the northern parts of the NKA to the north east towards the Nama Aquifer was validated. Due to the substantial water losses, the NKA is not a typical karst aquifer. While the project area receives an average rainfall of 170.36 mm/a, it was estimated that 1-14.24 % (maximum 24.43 mm/a) rainfall was available for recharge to the NKA. Actual recharge to the NKA was estimated to be less than 1-18.21 % (maximum 4.45 mm/a) reflecting the vast losses incurred by the NKA via discharge. This paper concluded that groundwater resources of the NKA were potentially finite. The possibility of developing the aquifer for bulk water supply would therefore drastically lower recharge to surrounding aquifers that sustain local populations because all received rainfall will be utilized to maximise recharge to the NKA instead of surrounding aquifers.

      PubDate: 2017-01-13T18:19:22Z
      DOI: 10.1016/j.pce.2016.12.002
       
  • Changes in ecosystem services associated with planting structures of
           cropland: a case study in Minle County in China
    • Authors: Yaqun Liu; Wei Song; Fengyun Mu
      Abstract: Publication date: Available online 11 January 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Yaqun Liu, Wei Song, Fengyun Mu
      The cropland ecosystem provides essential direct and indirect products and services to mankind such as food, fiber, biodiversity and soil conservation. A change of crop planting structure can change the ecosystem services of cropland by affecting land use type. In recent years, under the influence of regional comparative advantage and consumer demand changes, the crop planting structure in China has changed rapidly. However, there is still a lack of deep understanding on the effect of such a change in planting structure on the ecosystem services of cropland. Therefore, this research selected Minle County in the Heihe River Basin, which has small scattered croplands and a complex planting structure, as a study area. Based on the key time phase and optimal threshold of the normalized difference vegetation index (NDVI) data of the Thematic Mapper and Enhanced Thematic Mapper Plus (TM/ETM+) images, this study used the decision tree algorithm to classify and extract the crop planting structure in Minle County in 2007 and 2012 and to analyze the changes in its temporal and spatial patterns. Then, the market value method was adopted to estimate the effect of the change in crop planting structure on the ecosystem services of the cropland. From 2007–2012, the planting area of corn and rapeseed in Minle County increased by 5.86×103 ha and 5.10×103 ha, respectively. Conversely, the planting area of wheat and barley was reduced by 3.26×103 ha and 6.34×103 ha, respectively. These changes directly caused the increase of the ecosystem services value of corn and rapeseed by 1,062.82×104 USD and 842.54×104 USD, respectively. The resulting reduction in the ecosystem services value of wheat and barley was 488.24×104 USD and 828.29×104 USD, respectively. Besides, the total ecosystem services value of cropland increased by 1,564.98×104 USD. Further analysis found that the change in the crop planting structure caused an increase in the ecosystem services value of cropland of 359.44×104 USD, with a contribution rate of 22.97% to the total increase. The expansion of corn caused the increase of the ecosystem services value of cropland by 151.65×104 USD, with a contribution rate of 9.69% to the total increase. The change in crop planting structure in Minle County increased not only the economic benefits of crop planting, but also the ecosystem services of cropland.

      PubDate: 2017-01-13T18:19:22Z
      DOI: 10.1016/j.pce.2016.09.003
       
  • Assessment of heavy metals contamination in soil profiles of roadside
           Suaeda salsa wetlands in the Yellow River Delta, China
    • Authors: Xiaojun Wen; Qinggai Wang; Guangliang Zhang; Junhong Bai; Wei Wang; Shui Zhang
      Abstract: Publication date: Available online 4 January 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Xiaojun Wen, Qinggai Wang, Guangliang Zhang, Junhong Bai, Wei Wang, Shui Zhang
      Five sampling sites (Sites A, B, C, D, and E) were selected along a 250m sampling zone covered by Suaeda salsa, which was perpendicular to a road, in the Yellow River Delta of China. Soil profile samples were collected in these five sampling sites to investigate the profile distributions and toxic risks of heavy metals. Concentrations of heavy metals (As, Cd, Cr, Cu, Ni, Pb and Zn) were determined using inductively coupled plasma atomic absorption spectrometry (ICP-AAS). The results showed that in each sampling site, Cd, Cu, Pb and Zn have approximately constant concentrations along four soil layers and did not show high contamination compared with the values of probable effect levels (PELs). All soils exhibited As and Ni pollution at all sampling sites compared with other heavy metals. The index of geo-accumulation (Igeo) values for As in the 20-30cm soil layer at Site B was grouped into Class Ⅳ(2<Igeo≤3), indicating that the soil was moderately to strongly contaminated. Forty percent of Igeo values for all soil samples for Cd were grouped into Class Ⅳ(2<Igeo≤3) and 75% samples of Site C showed moderately to strongly polluted level. The Enrichment factor (EF) values of As at Sites B, C, D, and E reached significant enrichment level and EF values of Cd at five sampling sites all reached significant enrichment level. The sum of toxic units (∑TUs) values for surface soils of Sites B and C beyond 4 indicated that Sites B and C have severer toxicity compared with other three sampling sites. As and Ni should be paid more attention to avoid potential ecotoxicity due to their high contribution ratios to the ∑TUs in this Suaeda salsa wetland. Correlation analysis (CA) and principal components analysis (PCA) revealed that Cr, Cu, Ni, Pb and Zn might derive from the common sources, Cd might originate from another, while As might have more complex sources in this study area.

      PubDate: 2017-01-05T08:18:03Z
      DOI: 10.1016/j.pce.2017.01.001
       
  • Stimulation of nitrogen turnover due to nutrients release from aggregates
           affected by freeze-thaw in wetland soils
    • Authors: Yang Song; Yuanchun Zou; Guoping Wang; Xiaofei Yu
      Abstract: Publication date: Available online 29 December 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Yang Song, Yuanchun Zou, Guoping Wang, Xiaofei Yu
      The freeze-thaw phenomenon will occur more frequently in mid-high latitude ecosystems under climate change which has a remarkable effect on biogeochemical processes in wetland soils. Here, we used a wet sieving procedure and a barometric process separation (BaPS) technique to examine the responses of wetland soil aggregates and related carbon and nitrogen turnover affected by the freeze-thaw treatment. Wetland soil samples were divided into a treatment group and a control group. The treatment group was incubated at temperatures fluctuating from 10 °C to −10 °C, whereas the control group was incubated at the constant temperature of 10 °C. A 24 h process was set as the total freeze-thaw cycle, and the experiment had 20 continuous freeze-thaw cycles. In our results, the freeze-thaw process caused great destruction to the >2 mm water-stable aggregates (WSA) fraction and increased the <0.053 mm WSA fraction. The dissolved organic carbon (DOC) content was stimulated during the initial freeze-thaw cycles followed by a rapid decline, and then still increased during subsequent freeze-thaw cycles, which was mainly determined by the soil organic carbon (SOC). The NH4 + and NO3 − content, respiration rate and gross nitrification rate were all significantly improved by the freeze-thaw effect. Because the amount of NH4 + and NO3 − expressed prominent negative responses to the content of >2 mm WSA fraction and the gross nitrification rate can be stimulated at the initial freeze-thaw cycles, nutrients and substrates may play a leading role in the freeze-thaw treatment regardless of the minimal influences on microbial biomass pools.

      PubDate: 2017-01-05T08:18:03Z
      DOI: 10.1016/j.pce.2016.12.005
       
  • Impacts of sea cucumber farming on biogeochemical characteristics in the
           Yellow River estuary, Northern China
    • Authors: Jing Fu; Hisashi Yokoyama; Baoshan Cui; Jin Zhou; Jiaguo Yan; Xu Ma; Shozo Shibata
      Abstract: Publication date: Available online 28 December 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Jing Fu, Hisashi Yokoyama, Baoshan Cui, Jin Zhou, Jiaguo Yan, Xu Ma, Shozo Shibata
      To investigate the potential environmental effects of pond farming for Apostichopus japonicas in Yellow River estuary, we examined discrepancies of distance-based typical pollution indicators (TOC, TN, NO3 -, NH4 +, NO2 - and PO4 3-) and biochemical tracers (δ13C and δ15N) in water column and sediment, as well as dietary characteristics of dominant macrobenthos between farming and non-farming areas. The results revealed that studied variables in water column showed no uniform spatial differences. Meanwhile, those in sediments displayed similar decrease tendencies from farming pond to the adjacent tidal flat, which was considered to represent the environmental effects of farming. Biochemical tracers (δ13C and δ15N) in both water column and sediment confirmed the origin of organic matters from the aquaculture waste. The detectable dispersion distance of aquaculture waste was restricted to an area within 50 m distance as determined by most variables in sediment (TOC, TN, NO3 - and NH4 +), particularly by C/N ratio and δ13C with which origins of the wastes were traced. Bayesian mixing models indicated that in the farming area BMA had a larger contribution, while POM(marine) showed a smaller contribution to the diets of Helice tridens and Macrophthalmus abbreviates compared to those in the non-farming area. The overall results showed that pond farming for Apostichopus japonicus in the Yellow River estuary altered the local environment to a certain extent. For methodological consideration, sediment biogeochemical characteristics as a historical recorder much more effectively reflected aquaculture waste accumulation, and stable isotope approaches are efficient in tracing the origin and extent of various allogenous sources.

      PubDate: 2017-01-05T08:18:03Z
      DOI: 10.1016/j.pce.2016.12.006
       
 
 
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