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PHYSICS (581 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  [3040 journals]
  • 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
       
  • 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
       
  • 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
       
  • Detrimental effects of commercial zinc oxide and silver nanomaterials on
           bacterial populations and performance of wastewater systems
    • Authors: Anza-vhudziki Mboyi; Ilunga Kamika; MaggyN.B. Momba
      Abstract: Publication date: Available online 26 December 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Anza-vhudziki Mboyi, Ilunga Kamika, MaggyN.B. Momba
      The widespread use of commercial nanomaterials (NMs) in consumer products has raised environmental concerns as they can enter and affect the efficiency of the wastewater treatment plants. In this study the effect of various concentrations of zinc oxide NMs (nZnO) and silver NMs (nAg) on the selected wastewater bacterial species (Bacillus licheniformis, Brevibacillus laterosporus and Pseudomonas putida) was ascertained at different pH levels (pH 2, 7 and 10). Lethal concentrations (LC) of NMs and parameters such as chemical oxygen demand (COD) and dissolved oxygen (DO) were taken into consideration to assess the performance of a wastewater batch reactor. Bacterial isolates were susceptible to varying concentrations of both nZnO and nAg at pH 2, 7 and 10. It was found that a change in pH did not significantly affect the toxicity of test NMs towards target bacterial isolates. All bacterial species were significantly inhibited (p < 0.05) in the presence of 0.65 g/L of nZnO and nAg. In contrast, there was no significant difference (p > 0.05) in COD removal in the presence of increasing concentrations of NMs, which resulted in increasing releases of COD. Noticeably, there was no significant difference (p > 0.05) in the decrease in DO uptake in the presence of increasing NM concentrations for all bacterial isolates. The toxic effects of the target NMs on bacterial populations in wastewater may negatively impact the performance of biological treatment processes and may thus affect the efficiency of wastewater treatment plants in producing effluent of high quality.

      PubDate: 2017-01-05T08:18:03Z
      DOI: 10.1016/j.pce.2016.12.003
       
  • Hydrochemical modelling of water quality in terms of emerging
           micropollutants in Mpumalanga, Gauteng and North West Provinces
    • Authors: Elijah M.M. Wanda; Bhekie B. Mamba; Titus A.M. Msagati
      Abstract: Publication date: Available online 26 December 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Elijah M.M. Wanda, Bhekie B. Mamba, Titus A.M. Msagati
      Emerging micropollutants (EMPs) are ubiquitous in aquatic systems and are associated with a wide range of eco-toxicological effects worldwide. There remains a lack of scientific understanding of the major underlying hydrochemical factors behind variations in concentration heterogeneities of EMPs in time and space. This study was therefore conducted to determine major hydrochemical processes controlling water quality and the occurrence of EMPs mainly, carbamazepine (CBZ), tonalide (AHTN), galaxolide (HHCB), caffeine (CAF), technical 4-nonylphenol (NP) and bisphenol A (BPA) in water from Mpumalanga, Gauteng and North West Provinces in South Africa. Grab water samples were collected bi-monthly between June 2014 and April 2016 from 44 water sources using standard sampling procedures. BPA, NP, CAF, HHCB, AHTN, CBZ were extracted, cleaned and enriched using autotrace-SPE at neutral pH and analyzed using GC × GC-TOFMS. Kruskal Wallis-test was used to test for temporal variations in occurrence of the analytes. The Geochemist's Workbench® Release 11 software, Surfer Golden Graphics for surface mapping, PHREEQC software and bivariate ion plots were used determine the major hydrogeochemical processes. The mean concentrations of EMPs varied from 3.48 μg/L for CAF to 421.53 μg/L for HHCB. Although the Kruskal Wallis test revealed no any statistically significant temporal variations in concentrations of the analytes in water samples at 95% confidence level, their occurrence and distribution vary spatially with BPA being the most widely distributed EMP and was present in 62% of the sampled sites. Municipal waste water inputs, agricultural pollution, ion-exchange reactions, carbonate and silicate weathering were the major processes controlling water quality in the study area. This study may assist water resource managers to ably address and manage water pollution resulting from a number of natural and anthropogenic hydrochemical processes in the study area.

      PubDate: 2017-01-05T08:18:03Z
      DOI: 10.1016/j.pce.2016.12.004
       
  • Measuring environmental performance of industrial sub-sectors in China: a
           stochastic metafrontier approach
    • Authors: Yuping Bai; Xiangzheng Deng; Qian Zhang; Zhan Wang
      Abstract: Publication date: Available online 28 December 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Yuping Bai, Xiangzheng Deng, Qian Zhang, Zhan Wang
      In this paper, we quantitatively measure the environmental performance and potential capacities of carbon emission mitigation of 39 industrial sectors in China during 2005-2011 by adopting a stochastic metafrontier approach. We also analyze the differences of environmental performance and technology gap ratios (TGRs) across three categorized industrial groups. Cluster analysis of carbon intensity provides the categorized groups. The results show that due to neglect of technology gaps among the categorized groups, the environmental performance measured by a stochastic frontier approach (SFA) is underestimated. Comparison analysis infers that, relative to the metafrontier, the industrial sectors in Group 1 achieve the highest environmental performance and TGRs, while environmental performance and TGRs of industrial sectors in Group 3 is still at a low level for lack of advanced production technology. Industrial sectors also perform significant differences on potential capacities of carbon emission mitigation. We suggest that policies and regulations on industrial technology innovation and control of carbon emissions should be strengthened for eco-efficient and sustainable development.

      PubDate: 2017-01-05T08:18:03Z
      DOI: 10.1016/j.pce.2016.12.007
       
  • 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
       
  • 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
       
  • 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
       
  • Effects of drought and salt stresses on growth characteristics of
           Euhalophyte Suaeda salsa in coastal wetlands
    • Authors: Jia Jia; Chen Huang; Junhong Bai; Guangliang Zhang; Qingqing Zhao; Xiaojun Wen
      Abstract: Publication date: Available online 4 January 2017
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Jia Jia, Chen Huang, Junhong Bai, Guangliang Zhang, Qingqing Zhao, Xiaojun Wen
      The pot experiment was carried out in the Yellow River Delta to investigate the effects of drought and salt stresses on growth characteristics of Suaeda salsa, and to reveal the role of nitrogen (N) application in alleviation effects of drought and salt stresses on Suaeda salsa in coastal wetlands. In this study, plants were exposed to two water contents treatments (i.e., 14 % and 26 % water content), four salinity treatments (i.e., 2 g/kg, 4 g/kg, 6 g/kg, and 8 g/kg NaCl) and two N application treatments (i.e., 0 and 200 N mg/kg) in field conditions. Growth characteristics of Suaeda salsa were assessed as fresh weight, dry weight, height, total nitrogen (TN) and total carbon (TC). Our results showed that fresh weight, dry weight and height of Suaeda salsa promoted at lower salinity treatments but reduced at higher salinity treatments, while TN and TC contents kept stable with increasing salinity levels. Drought stress diminished the fresh weight, dry weight and height of Suaeda salsa, whereas enhanced TN contents. Under the interactive stresses of drought and salt, fresh weight and dry weight showed slight increases at lower salinity treatments, whereas decreases at higher salinity treatments. N application promoted the fresh weight, dry weight and TN contents other than the height and TC contents of Suaeda salsa. The interaction between N application and salt stress exhibited a significant influence on the fresh weight and dry weight of Suaeda salsa, whereas no significant interaction between N application and drought stress was observed. These findings of this study suggested that higher salinity, drought and the interaction of drought and higher salt stresses would retard the growth of Suaeda salsa, whereas N application could only mitigate the deleterious effects of salt stress on Suaeda salsa.

      PubDate: 2017-01-05T08:18:03Z
      DOI: 10.1016/j.pce.2017.01.002
       
  • Water productivity and integrated water resources management
    • Authors: Xiangzheng Deng; R.B. Singh; Junguo Liu; Burak Güneralp
      First page: 1
      Abstract: Publication date: December 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 96
      Author(s): Xiangzheng Deng, R.B. Singh, Junguo Liu, Burak Güneralp


      PubDate: 2016-12-04T02:21:53Z
      DOI: 10.1016/j.pce.2016.11.002
      Issue No: Vol. 96 (2016)
       
  • Strategy for management of lake-catchment system integrated with natural
           and anthropogenic factors in China
    • Authors: Zhandong Yang; Feng Wu; Xing Gao
      Pages: 26 - 33
      Abstract: Publication date: December 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 96
      Author(s): Zhandong Yang, Feng Wu, Xing Gao
      Lake eutrophication that has caused severe damages to aquatic ecosystems is a hot issue in the field of water pollution control, so analyzing its process and driving mechanism is of great significance. In this study, we detected its major driving factors based on an observed dataset and assessed the impacts of these factors. Firstly, empirical econometric models were used to ascertain the Per capita GDP and the percentage of impervious surface, which are significantly related with the eutrophication level. Eutrophication is slightly affected by anthropogenic disturbance, but is negatively related to the supply coefficient. Secondly, all driving factors are divided into two categories, including the stresses caused by human activities and the comprehensive health status, which are expressed as the two coordinate axes of an indicator-matrix. Thirdly, lake classification, which is a decision-making tool for management and control of eutrophication, suggests a breakdown in communication between researchers and water managers. Finally, corresponding management strategies are recommended, and the classification system can be used to simplify management by grouping lakes that may be managed by similar strategies. The classification management may enlighten and guide the appropriate policy implementation for lake eutrophication management.

      PubDate: 2016-12-04T02:21:53Z
      DOI: 10.1016/j.pce.2016.06.006
      Issue No: Vol. 96 (2016)
       
  • The sustainability of drinking water supply in rural China: Does the
           provision of drinking water investment mismatch the demand of residents?
    • Authors: Ying Liu; Tang Yao; Yunli Bai; Yu Liu
      Pages: 34 - 40
      Abstract: Publication date: December 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 96
      Author(s): Ying Liu, Tang Yao, Yunli Bai, Yu Liu
      It is doubted that the top down nature of investment planning may lead to mismatches between drinking water investment and the demands of local residents in rural China. Statistical and econometric analysis based on data of 2020 rural households from five Chinese provinces from 1998 to 2011 are used to illustrate the linkage between demand for drinking water investment and construction of drinking water projects. Household's demand significantly affects drinking water projects implemented by upper level governments and implemented jointly, but is not significant in explaining the projects implemented by village. There is evidence to suggest that the demands of local leaders override those of households in the implementation of drinking water projects provided by village in the early stage of 2005–2008. The situation improves in the latter stage of 2008–2011when the village level participatory bodies begin to provide opportunities for households to voice their preferences on public goods investment. The results of this study imply that it is important to explore appropriate regulations and policies that enabling local cadres to better meet local demands of their communities to ensure the sustainability of rural drinking water supply.

      PubDate: 2016-12-04T02:21:53Z
      DOI: 10.1016/j.pce.2016.07.002
      Issue No: Vol. 96 (2016)
       
  • Long time-series spatiotemporal variations of NPP and water use efficiency
           in the lower Heihe River Basin with serious water scarcity
    • Authors: Haiming Yan; Jinyan Zhan; Huicai Yang; Fan Zhang; Guofeng Wang; Wenjie He
      Pages: 41 - 49
      Abstract: Publication date: December 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 96
      Author(s): Haiming Yan, Jinyan Zhan, Huicai Yang, Fan Zhang, Guofeng Wang, Wenjie He
      It is of great significance to analyze the long time-series spatiotemporal dynamics of water use efficiency (WUE) to formulating appropriate management measures in response to the growing water scarcity in arid and semi-arid regions. This study analyzed the long time-series variations of WUE in the Lower Heihe River Basin, a typical arid and semi-arid region in China. The net primary productivity (NPP) was first estimated with the C-fix model, then WUE during 2001–2010 was calculated with the NPP and evapotranspiration (ET) data, and the accumulative WUE was further calculated. The results showed that the annual NPP and WUE in the study area ranged from zero to 448.70 gC/(m2 a) and from zero to 2.20 gC kg−1 H2O, respectively, both of which showed an overall increasing trend during 2001–2010. Besides, the spatial pattern of WUE kept overall unchanged during 2001–2010, but with remarkable change in some part of the study area. In addition, the accumulative WUE of the whole study area showed a first sharply decreasing and then gradually increasing trend, but there was still some scope to improve the WUE, and it is necessary to carry out some more specific policies to further improve the water allocation and WUE within the Lower Heihe River Basin. Although with some uncertainties, these results still can provide valuable reference information for improving the water resource management and ecological conservation to guarantee provision of essential ecosystem services in arid and semi-arid regions.

      PubDate: 2016-12-04T02:21:53Z
      DOI: 10.1016/j.pce.2016.06.003
      Issue No: Vol. 96 (2016)
       
  • Allocating agricultural production factors: A scenario-based modeling of
           wheat production in Shandong Province, China
    • Authors: Fan Zhang; Jinyan Zhan; Qian Zhang; Haiming Yan; Zhongxiao Sun
      Pages: 55 - 63
      Abstract: Publication date: December 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 96
      Author(s): Fan Zhang, Jinyan Zhan, Qian Zhang, Haiming Yan, Zhongxiao Sun
      We aim to determine the effects of agricultural factors input per hectare on wheat production, and to optimize the allocation of wheat production factors under three scenarios and in different operating modes. Data were collected from 204 farming households using a face-to-face questionnaire. The sampled farms were selected through a stratified random sampling technique. We find fertilizer cost, irrigation cost and machinery cost all positively and significantly affect the per-unit-area wheat production, indicating the labor cost is not the major driving factor on wheat yield increment. Multi-object optimization model is used to allocate the production factors per hectare. We find under the Business as usual (BAU) scenario, the irrigation cost per-hectare wheat production after optimization in 2014 grows at a rate of 24.31% and accounts for 14.9% of total input. Under the Cooperate Environmental Sustainability (CES) scenario, the fertilizer and pesticide costs after optimization drop significantly by 42.83% and 21.41%, respectively. Under the Rapid Benefit Growth (RBG) scenario, the irrigation cost after optimization increase by 2.56% and the fertilizer cost increases by 4.69% compared with the surveyed data. Comparison of optimized data among three operating modes shows that the labor costs at household farm and cooperative farm both increase significantly. Cooperative farms are more successful in production factor use efficiency and economic performance. In conclusion, wheat production at different operating modes could be improved so as to constitute more efficient and economic use of production factors.

      PubDate: 2016-12-04T02:21:53Z
      DOI: 10.1016/j.pce.2016.06.002
      Issue No: Vol. 96 (2016)
       
  • The impact of land use change on water balance in Zhangye city, China
    • Authors: Zhongxiao Sun; Feng Wu; Chenchen Shi; Jinyan Zhan
      Pages: 64 - 73
      Abstract: Publication date: December 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 96
      Author(s): Zhongxiao Sun, Feng Wu, Chenchen Shi, Jinyan Zhan
      Land use change has a significant effect on water balance, especially in arid region, such as Northwest China. In this paper, we analyze the effect of land use change on water balance in terms of the amount of water supply and demand from economic perspective. It's the first time to extend the basic 48 sectors input-output table to include water and land accounts that involved into multiple production processes for Zhangye city. We then perform the improved ORANI-G model, a single region Computable General Equilibrium (CGE) model, to analyze the effect of land use change on water balance under three scenarios. Subsequently, scenario-based simulation results are interpreted through selected sectors from agricultural, industrial, and service sectors respectively. Finally, the effect of land use change on water balance is analyzed through the difference between business-as-usual and land use unchanged scenarios. The results show that the extent of effect on water balance is different among sectors. Specifically, from the perspective of absolute value, service sectors are the largest, followed by industrial sectors, and the agricultural sectors are the least. Conversely, in terms of percentage change of land use, the largest extent of effect occurs in agricultural sectors. Additionally, with the rapid urbanization and the development of social economy, water balance in industrial sectors and service sectors will be stricken and reconstructed to a new high level. Simulation results also show that agricultural land shrinking will mitigate water scarcity distinctly, which indicates that balance the relationship among different stakeholders is imperative to guarantee water transformation from agricultural sectors to industrial and service sectors.

      PubDate: 2016-12-04T02:21:53Z
      DOI: 10.1016/j.pce.2016.06.004
      Issue No: Vol. 96 (2016)
       
  • Retraction notice to “Status of groundwater arsenic pollution in
           Holocene aquifers from parts of the Ghaghara Basin, India: Its relation to
           geomorphology and hydrogeological setting”[Phys. Chem. Earth 58–60C
           (2013) 68–76]
    • Authors: Babar Ali Shah
      First page: 84
      Abstract: Publication date: December 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 96
      Author(s): Babar Ali Shah


      PubDate: 2016-12-04T02:21:53Z
      DOI: 10.1016/j.pce.2015.02.001
      Issue No: Vol. 96 (2016)
       
  • Studying seismic sources: Theory, methods and applications
    • Authors: Seabstiano D'Amico; Christos Evangelidis; Efthimios Sokos
      First page: 1
      Abstract: Publication date: October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 95
      Author(s): Seabstiano D'Amico, Christos Evangelidis, Efthimios Sokos


      PubDate: 2016-11-06T15:24:23Z
      DOI: 10.1016/j.pce.2016.10.009
      Issue No: Vol. 95 (2016)
       
  • A ten year Moment Tensor database for Western Greece
    • Authors: Anna Serpetsidaki; Efthimios Sokos; G-Akis Tselentis
      Pages: 2 - 9
      Abstract: Publication date: October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 95
      Author(s): Anna Serpetsidaki, Efthimios Sokos, G-Akis Tselentis
      Moment Tensors (MTs) provide important information for seismotectonic, stress distribution and source studies. It is also important as a real time or near real time information in shakemaps, tsunami warning, and stress transfer. Therefore a reliable and rapid MT computation is a routine task for modern seismic networks with broadband sensors and real-time digital telemetry. In this paper we present the database of Moment Tensor solutions computed during the last ten years in Western Greece by the University of Patras, Seismological Laboratory (UPSL). The data from UPSL broad band network were used together with the ISOLA Moment Tensor inversion package for routine MT calculation. The procedures followed and the comparison of UPSL derived solutions with the ones provided by other agencies for Western Greece region are presented as well. The Moment Tensor database includes solutions for events in the magnitude range 2.8–6.8 and provides a unique insight into the faulting characteristics of Western Greece. Moreover it paves the way for detailed studies of stress tensor and stress transfer. The weak events' Moment Tensor included in UPSL's database are important for the comprehension of local seismotectonics and reveal the role of minor faults, which may be critical in seismic hazard estimation.

      PubDate: 2016-11-06T15:24:23Z
      DOI: 10.1016/j.pce.2016.04.007
      Issue No: Vol. 95 (2016)
       
  • Seismic moment tensor inversion using 3D velocity model and its
           application to the 2013 Lushan earthquake sequence
    • Authors: Lupei Zhu; Xiaofeng Zhou
      Pages: 10 - 18
      Abstract: Publication date: October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 95
      Author(s): Lupei Zhu, Xiaofeng Zhou
      Source inversion of small-magnitude events such as aftershocks or mine collapses requires use of relatively high frequency seismic waveforms which are strongly affected by small-scale heterogeneities in the crust. In this study, we developed a new inversion method called gCAP3D for determining general moment tensor of a seismic source using Green's functions of 3D models. It inherits the advantageous features of the “Cut-and-Paste” (CAP) method to break a full seismogram into the Pnl and surface-wave segments and to allow time shift between observed and predicted waveforms. It uses grid search for 5 source parameters (relative strengths of the isotropic and compensated-linear-vector-dipole components and the strike, dip, and rake of the double-couple component) that minimize the waveform misfit. The scalar moment is estimated using the ratio of L 2 norms of the data and synthetics. Focal depth can also be determined by repeating the inversion at different depths. We applied gCAP3D to the 2013 M s 7.0 Lushan earthquake and its aftershocks using a 3D crustal-upper mantle velocity model derived from ambient noise tomography in the region. We first relocated the events using the double-difference method. We then used the finite-differences method and reciprocity principle to calculate Green's functions of the 3D model for 20 permanent broadband seismic stations within 200 km from the source region. We obtained moment tensors of the mainshock and 74 aftershocks ranging from M w 5.2 to 3.4. The results show that the Lushan earthquake is a reverse faulting at a depth of 13–15 km on a plane dipping 40–47° to N46° W. Most of the aftershocks occurred off the main rupture plane and have similar focal mechanisms to the mainshock's, except in the proximity of the mainshock where the aftershocks' focal mechanisms display some variations.

      PubDate: 2016-11-06T15:24:23Z
      DOI: 10.1016/j.pce.2016.01.002
      Issue No: Vol. 95 (2016)
       
  • Moment tensors, state of stress and their relation to faulting processes
           in Gujarat, western India
    • Authors: Sandeep Kumar Aggarwal; Prosanta Kumar Khan; Sarada Prasad Mohanty; Zafeiria Roumelioti
      Pages: 19 - 35
      Abstract: Publication date: October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 95
      Author(s): Sandeep Kumar Aggarwal, Prosanta Kumar Khan, Sarada Prasad Mohanty, Zafeiria Roumelioti
      Time domain moment tensor analysis of 145 earthquakes (Mw 3.2 to 5.1), occurring during the period 2006–2014 in Gujarat region, has been performed. The events are mainly confined in the Kachchh area demarcated by the Island belt and Kachchh Mainland faults to its north and south, and two transverse faults to its east and west. Libraries of Green's functions were established using the 1D velocity model of Kachchh, Saurashtra and Mainland Gujarat. Green's functions and broadband displacement waveforms filtered at low frequency (0.5–0.8 Hz) were inverted to determine the moment tensor solutions. The estimated solutions were rigorously tested through number of iterations at different source depths for finding reliable source locations. The identified heterogeneous nature of the stress fields in the Kachchh area allowed us to divide this into four Zones 1–4. The stress inversion results indicate that the Zone 1 is dominated with radial compression, Zone 2 with strike-slip compression, and Zones 3 and 4 with strike-slip extensions. The analysis further shows that the epicentral region of 2001MW 7.7 Bhuj mainshock, located at the junction of Zones 2, 3 and 4, was associated with predominant compressional stress and strike-slip motion along ∼ NNE-SSW striking fault on the western margin of the Wagad uplift. Other tectonically active parts of Gujarat (e.g. Jamnagar, Talala and Mainland) show earthquake activities are dominantly associated with strike-slip extension/compression faulting. Stress inversion analysis shows that the maximum compressive stress axes (σ1) are vertical for both the Jamnagar and Talala regions and horizontal for the Mainland Gujarat. These stress regimes are distinctly different from those of the Kachchh region.

      PubDate: 2016-11-06T15:24:23Z
      DOI: 10.1016/j.pce.2016.01.004
      Issue No: Vol. 95 (2016)
       
  • State of tectonic stress in Shillong Plateau of northeast India
    • Authors: Santanu Baruah; Saurabh Baruah; Sowrav Saikia; Mahesh N. Shrivastava; Antara Sharma; C.D. Reddy; J.R. Kayal
      Pages: 36 - 49
      Abstract: Publication date: October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 95
      Author(s): Santanu Baruah, Saurabh Baruah, Sowrav Saikia, Mahesh N. Shrivastava, Antara Sharma, C.D. Reddy, J.R. Kayal
      Tectonic stress regime in the Shillong plateau, northeast region of India, is examined by stress tensor inversion. Some 97 reliable fault plane solutions are used for stress inversion by the Michael and Gauss methods. Although an overall NNW-SSE compressional stress is observed in the area, the stress regime varies from western part to eastern part of the plateau. The eastern part of the plateau is dominated by NNE-SSW compression and the western part by NNW-SSE compression. The NNW-SSE compression in the western part may be due to the tectonic loading induced by the Himalayan orogeny in the north, and the NNE-SSW compression in the eastern part may be attributed to the influence of oblique convergence of the Indian plate beneath the Indo-Burma ranges. Further, Gravitational Potential Energy (GPE) derived stress also indicates a variation from west to east.

      PubDate: 2016-11-06T15:24:23Z
      DOI: 10.1016/j.pce.2015.11.009
      Issue No: Vol. 95 (2016)
       
  • On the spatial distribution of seismicity and the 3D tectonic stress field
           in western Greece
    • Authors: Ioannis Kassaras; Vasilis Kapetanidis; Andreas Karakonstantis
      Pages: 50 - 72
      Abstract: Publication date: October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 95
      Author(s): Ioannis Kassaras, Vasilis Kapetanidis, Andreas Karakonstantis
      We analyzed a large number of focal mechanisms and relocated earthquake hypocenters to investigate the geodynamics of western Greece, the most seismically active part of the Aegean plate-boundary zone. This region was seismically activated multiple times during the last decade, providing a large amount of enhanced quality new information that was obtained by the Hellenic Unified Seismological Network (HUSN). Relocated seismicity using a double-difference method appears to be concentrated above ∼35 km depth, exhibiting spatial continuity along the convergence boundary and being clustered elsewhere. Earthquakes are confined within the accreted sediments escarpment of the down-going African plate against the un-deformed Eurasian hinterland. The data arrangement shows that Pindos constitutes a seismic boundary along which large stress heterogeneities occur. In Cephalonia no seismicity is found to be related with the offshore Cephalonia Transform Fault (CTF). Onshore, NS crustal extension dominates, while in central and south Peloponnesus the stress field appears rotated by 90°. Shearing-stress obliquity by 30° is indicated along the major strike-slip faults, consistent with clockwise crustal rotation. Within the lower crust, the stress field appears affected by plate kinematics and distributed deformation of the lower crust and upper mantle, which guide the regional geodynamics.

      PubDate: 2016-11-06T15:24:23Z
      DOI: 10.1016/j.pce.2016.03.012
      Issue No: Vol. 95 (2016)
       
  • The typical seismic behavior in the vicinity of a large earthquake
    • Authors: M.V. Rodkin; I.N. Tikhonov
      Pages: 73 - 84
      Abstract: Publication date: October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 95
      Author(s): M.V. Rodkin, I.N. Tikhonov
      The Global Centroid Moment Tensor catalog (GCMT) was used to construct the spatio-temporal generalized vicinity of a large earthquake (GVLE) and to investigate the behavior of seismicity in GVLE. The vicinity is made of earthquakes falling into the zone of influence of a large number (100, 300, or 1000) of largest earthquakes. The GVLE construction aims at enlarging the available statistics, diminishing a strong random component, and revealing typical features of pre- and post-shock seismic activity in more detail. As a result of the GVLE construction, the character of fore- and aftershock cascades was examined in more detail than was possible without of the use of the GVLE approach. As well, several anomalies in the behavior exhibited by a variety of earthquake parameters were identified. The amplitudes of all these anomalies increase with the approaching time of the generalized large earthquake (GLE) as the logarithm of the time interval from the GLE occurrence. Most of the discussed anomalies agree with common features well expected in the evolution of instability. In addition to these common type precursors, one earthquake-specific precursor was found. The decrease in mean earthquake depth presumably occurring in a smaller GVLE probably provides evidence of a deep fluid being involved in the process. The typical features in the evolution of shear instability as revealed in GVLE agree with results obtained in laboratory studies of acoustic emission (AE). The majority of the anomalies in earthquake parameters appear to have a secondary character, largely connected with an increase in mean magnitude and decreasing fraction of moderate size events (mw5.0–6.0) in the immediate GLE vicinity. This deficit of moderate size events could hardly be caused entirely by their incomplete reporting and can presumably reflect some features in the evolution of seismic instability.

      PubDate: 2016-11-06T15:24:23Z
      DOI: 10.1016/j.pce.2016.04.001
      Issue No: Vol. 95 (2016)
       
  • Analysis of the 2012–2013 Torreperogil-Sabiote seismic swarm
    • Authors: M. Hamdache; J.A. Peláez; J. Henares; Y. Damerdji; R. Sawires
      Pages: 101 - 112
      Abstract: Publication date: October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 95
      Author(s): M. Hamdache, J.A. Peláez, J. Henares, Y. Damerdji, R. Sawires
      This study analyses the temporal clustering, spatial clustering, and statistics of the 2012–2013 Torreperogil-Sabiote (southern Spain) seismic swarm. During the swarm, more than 2200 events were located, mostly at depths of 2–5 km, with magnitude event up to m bLg 3.9 (M w 3.7). On the basis of daily activity rate, three main temporal phases are identified and analysed. The analysis combines different seismological relationships to improve our understanding of the physical processes related to the swarm's occurrence. Each temporal phase is characterized by its cumulative seismic moment. Using several different approaches, we estimate a catalog completeness magnitude of m c ≅ 1.5. The maximum likelihood b-value estimates for each swarm phase are 1.11 ± 0.09, 1.04 ± 0.04, and 0.90 ± 0.04, respectively. To test the hypothesis that a b-value decrease is a precursor to a large event, we study temporal variations in b-value using overlapping moving windows. A relationship can be inferred between change in b-value and the regime style of the rupture. b-values are indicators of the stress regime, and influence the size of ruptures. The fractal dimension D 2 is used to perform spatial analysis. Cumulative gamma and beta functions are used to analyse the behaviour of inter-event distances during the earthquake sequence.

      PubDate: 2016-11-06T15:24:23Z
      DOI: 10.1016/j.pce.2016.01.003
      Issue No: Vol. 95 (2016)
       
  • Rethinking the role of edaphic condition in halophyte vegetation
           degradation on salt marshes due to coastal defense structure
    • Authors: Tian Xie; Baoshan Cui; Junhong Bai; Shanze Li; Shuyan Zhang
      Abstract: Publication date: Available online 9 December 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Tian Xie, Baoshan Cui, Junhong Bai, Shanze Li, Shuyan Zhang
      Determining how human disturbance affects plant community persistence and species conservation is one of the most pressing ecological challenges. The large-scale disturbance form defense structures usually have a long-term and potential effect on phytocommunity in coastal saltmarshes. Coastal defense structures usually remove the effect of tidal wave on tidal salt marshes. As a consequence, edaphic factors such as the salinity and moisture contents are disturbed by tidal action blocking. However, few previous studies have explicitly addressed the response of halophyte species persistence and dynamics to the changing edaphic conditions. The understanding of the response of species composition in seed banks and aboveground vegetation to the stress is important to identify ecological effect of coastal defense structures and provide usefully insight into restoration. Here, we conducted a field study to distinguish the density, species composition and relationships of seed bank with aboveground vegetation between tidal flat wetlands with and without coastal defense structures. We also addressed the role of edaphic condition in vegetation degradation caused by coastal defense structures in combination with field monitor and greenhouse experiments. Our results showed the density of the seed bank and aboveground vegetation in the tidal flat without coastal defense structures was significantly lower than the surrounded flat with coastal defense structures. A total of 14 species were founded in the surrounded flat seed bank and 11 species in the tidal flat, but three species were only recorded in aboveground vegetation of the tidal flat which was much lower than 24 aboveground species in the surrounded flat. The absent of species in aboveground vegetation contributed to low germination rate which depend on the edaphic condition. The germination of seeds in the seed bank were inhabited by high soil salinity in the tidal flat and low soil moisture in the surrounded flat. Our study supported the hypothesis that the change of edaphic condition caused by coastal defense structures was the main reason for the difference of the species composition similarity between aboveground vegetation and the soil seed bank between the tidal and surrounded flats. Therefore, mitigating the hydrological disturbance and maintaining the original state of edaphic factors would be useful implications for reducing the ecological effect of defense structure to vegetation communities in coastal salt marshes.

      PubDate: 2016-12-11T03:02:56Z
      DOI: 10.1016/j.pce.2016.12.001
       
  • 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
      Abstract: Publication date: Available online 29 November 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      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: 2016-12-04T02:21:53Z
      DOI: 10.1016/j.pce.2016.11.004
       
  • 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
      Abstract: Publication date: Available online 24 November 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      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: 2016-11-27T15:42:03Z
      DOI: 10.1016/j.pce.2016.11.003
       
  • Living with floods – household perception and satellite observations in
           the Barotse Floodplain, Zambia
    • Authors: Xueliang Cai; Alemseged Haile; James Magidi; Everisto Mapedza; Luxon Nhamo
      Abstract: Publication date: Available online 11 November 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Xueliang Cai, Alemseged Haile, James Magidi, Everisto Mapedza, Luxon Nhamo
      The Barotse Floodplain, a designated Ramsar site, is home to thousands of indigenous people along with an extensive wetland ecosystem and food production system. Increasingly it is also a popular tourist destination with its annual Kuomboka festival which celebrates the relocation of the king and the Lozi people to higher ground before the onset of the flood season. This paper presents an integrated approach which cross validates and combines the floodplain residents’ perceptions about recent floods with information on flood inundation levels derived from satellite observations. Local residents’ surveys were conducted to assess farmers’ perception on the flooding patterns and the impact on their livelihoods. Further, a series of flood inundation maps from 1989 to 2014 generated from remotely sensed Landsat imagery were used to assess the recent patterns of floods. Results show that the floodplain has a population of 33 thousand living in 10849 small permeant or temporary buildings with a total cropland area of 4976 ha. The floodplain hydrology and flooding patterns have changed, confirmed by both surveys and satellite image analysis, due to catchment development and changing climate. The average annual inundated areas have increased from about 316 thousand ha in 1989-1998 to 488 thousand ha in 2005-2014. As a result the inundated cropland and houses increased from 9% and 6% in 1989 to 73% and 47% in 2014, respectively. The timing of the floods has also changed with both delaying and early onset happening more frequently. These changes cause increasing difficulties in flood forecast and preparation using indigenous knowledge, therefore creating greater damages to crops, livestock, and houses. Current floodplain management system is inadequate and new interventions are needed to help manage the floods at a systematic manner.

      PubDate: 2016-11-13T15:32:01Z
      DOI: 10.1016/j.pce.2016.10.011
       
  • 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
      Abstract: Publication date: Available online 11 November 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      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: 2016-11-13T15:32:01Z
      DOI: 10.1016/j.pce.2016.11.001
       
  • Modelling phytoremediation of nitrogen-polluted water using water hyacinth
           (Eichhornia crassipes)
    • Authors: Aloyce W. Mayo; Emmanuel E. Hanai
      Abstract: Publication date: Available online 30 October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Aloyce W. Mayo, Emmanuel E. Hanai
      Water hyacinth (Eichhornia crassipes) has a great potential for purification of wastewater through physical, chemical and biological mechanisms. In an attempt to improve the quality of effluents discharged from waste stabilization ponds at the University of Dar es Salaam, a pilot plant was constructed to experiment the effectiveness of this plants for transformation and removal of nitrogen. Samples of wastewater were collected and examined for water quality parameters, including pH, temperature, dissolved oxygen, and various forms of nitrogen, which were used as input parameters in a kinetic mathematical model. A conceptual model was then developed to model various processes in the system using STELLA 6.0.1 software. The results show that total nitrogen was removed by 63.9%. Denitrification contributed 73.8% of the removed nitrogen. Other dominant nitrogen removal mechanisms are net sedimentation and uptake by water hyacinth, which contributed 16.7% and 9.5% of the removed nitrogen, respectively. The model indicated that in presence of water hyacinth biofilm about 1.26 g Nm-2day-1 of nitrogen was removed. However, in the absence of biofilm in water hyacinth pond, the permanent nitrogen removal was only 0.89 g Nm-2day-1. This suggests that in absence of water hyacinth, the efficiency of nitrogen removal would decrease by 29.4%.

      PubDate: 2016-11-06T15:24:23Z
      DOI: 10.1016/j.pce.2016.10.016
       
  • Development of probabilistic operating rules for Hluhluwe Dam, South
           Africa
    • Authors: J. Ndiritu; J. Odiyo; R. Makungo; B. Mwaka; N. Mthethwa; C. Ntuli; A. Andanje
      Abstract: Publication date: Available online 30 October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): J. Ndiritu, J. Odiyo, R. Makungo, B. Mwaka, N. Mthethwa, C. Ntuli, A. Andanje
      Hluhluwe Dam, with a 30 million m3 reservoir that supplies water for irrigation and Hluhluwe municipality in Kwa-Zulu Natal Province, South Africa, was consistently experiencing low storage levels over several non-drought years since 2001. The dam was operated by rules of thumb and there were no records of water releases for irrigation - the main user of the dam. This paper describes an assessment of the historic behaviour of the reservoir since its completion in 1964 and the development of operating rules that accounted for: i) the multiple and different levels of reliability at which municipal and irrigation demands need to be supplied, and ii) inter-annual and inter-decadal variability of climate and inflows into the dam. The assessment of the behaviour of the reservoir was done by simulation assuming trigonometric rule curves that were optimized to maximize both yield and storage state using the SCE-UA method. The resulting reservoir behaviour matched the observed historic trajectory reasonably well and indicated that the dam has mainly been operated at a demand of 10 million m3/year until 2000 when the demand suddenly rose to 25 million m3/year. Operating rules were developed from a statistical analysis of the base yields from 500 simulations of the reservoir each using 5 year-long stochastically generated sequences of inflows, rainfall and evaporation. After the implementation of the operating rules in 2009, the storage state of the dam improved and matched those of other reservoirs in the region that had established operating rules.

      PubDate: 2016-11-06T15:24:23Z
      DOI: 10.1016/j.pce.2016.10.017
       
  • Electrospun polyacrylonitrile nanofibers functionalized with EDTA for
           adsorption of ionic dyes
    • Authors: E.F.C. Chaúque; J.C. Ngila; Adedeji A. Adelodun; C.J. Greyling; L.N. Dlamini
      Abstract: Publication date: Available online 1 November 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): E.F.C. Chaúque, J.C. Ngila, Adedeji A. Adelodun, C.J. Greyling, L.N. Dlamini
      The manipulation of nanofibers’ surface chemistry could enhance their potential application toward the removal of ionic dyes in wastewater. For this purpose, surface modification of electrospun polyacrylonitrile (PAN) nanofibers with ethylenediaminetetraacetic acid (EDTA) and ethylenediamine (EDA) crosslinker was experimented. The functionalized EDTA-EDA-PAN nanofibers were characterized using Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) technique. The impregnation of EDA and EDTA chelating agents on the surface of PAN changed the distribution of nanofibers as proximity is increased (accompanied by reduced softness), but the nanofibrous structure of the pristine PAN nanofibers was not substantially altered. Adsorption equilibrium studies were performed with Freundlich, Langmuir and Temkin isotherm models with the former providing better correlation to the experimental data. The modified PAN nanofibers showed efficient sorption of methyl orange (MO) and reactive red (RR) from aqueous synthetic samples, evinced by the maximum adsorption capacities (at 25 ºC) of 99.15 and 110.0 mg g-1, respectively. The fabricated nanofibers showed appreciable removal efficiency of the target dye sorptives from wastewater. However, the presence of high metal ions content affected the overall extraction of dyes from wastewater due to the depletion of the adsorbent´s active adsorptive sites.

      PubDate: 2016-11-06T15:24:23Z
      DOI: 10.1016/j.pce.2016.10.008
       
  • H/V measurements as an effective tool for the reliable detection of
           landslide slip surfaces: Case studies of Castagnola (La Spezia, Italy) and
           Roccalbegna (Grosseto, Italy)
    • Authors: Veronica Pazzi; Luca Tanteri; Gabriele Bicocchi; Michele D'Ambrosio; Andrea Caselli; Riccardo Fanti
      Abstract: Publication date: Available online 25 October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Veronica Pazzi, Luca Tanteri, Gabriele Bicocchi, Michele D'Ambrosio, Andrea Caselli, Riccardo Fanti
      A variety of methods (detailed geomorphological surveys, geotechnical investigations, local instrumentation, satellite data, and radar interferometry) along with geophysical techniques may be used to investigate slope instabilities and to detect the inhomogeneities of materials as well as their properties, boundaries, and sliding surfaces. Of these techniques, the method based on seismic noise measurements allows abrupt changes in seismic impedance at landslide boundaries resulting from varying levels of seismic velocity and material density to be detected. Peaks of the Horizontal to Vertical Spectral Ratio have proven to serve as effective indicators of the resonance frequency of low-impedance surface layers. In this work, horizontal to vertical spectral ratio surveys of the Castagnola (La Spezia, Italy) and Roccalbegna (Grosseto, Italy) landslides were carried out. From roughly 100 single-station measurements made inside and outside the landslides at each site, we define a threshold number of single-station seismic noise measures beyond which information is redundant because the variation in reconstructed impedance contrast surfaces is not significant. This approach allows one to reliably retrieve the geometry of a landslide body, ultimately generating useful information for determining whether further measurements are needed to improve landslide body reconstruction.

      PubDate: 2016-10-30T14:59:47Z
      DOI: 10.1016/j.pce.2016.10.014
       
  • A multidisciplinary approach to the seismic characterization of a mountain
           top (Monteluco, central Italy)
    • Authors: F. Durante; G. Di Giulio; M. Tallini; G. Milana; L. Macerola
      Abstract: Publication date: Available online 25 October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): F. Durante, G. Di Giulio, M. Tallini, G. Milana, L. Macerola
      This study provides a seismic characterization of the flat top area of Monteluco carbonate mountain using a multidisciplinary approach. Recordings of ambient vibrations and local earthquakes, geophysical and borehole data, detailed geological surveys and rock mass characterizations were used to investigate the ground-motion amplification observed on the flat top of Monteluco. Weak motion measurements carried out on the top area gave resonance frequency (f0) in the range of 2–4 Hz, likely due to the occurrence of fractured rocks, tens of meters thick. In this frequency range and in the same target area, it was also possible to observe a nearly NW-SE polarization of the seismic signal, which we have tentatively correlated with the main mapped fault systems. Nevertheless, a topographic effect on noise polarization cannot be excluded.

      PubDate: 2016-10-30T14:59:47Z
      DOI: 10.1016/j.pce.2016.10.015
       
  • Results from shallow geophysical investigations in the northwestern sector
           of the island of Malta
    • Authors: M. Pischiutta; F. Villani; S. D’Amico; M. Vassallo; F. Cara; D. Di Naccio; D. Farrugia; G. Di Giulio; S. Amoroso; L. Cantore; A. Mercuri; D. Famiani; P. Galea; A. Akinci; A. Rovelli
      Abstract: Publication date: Available online 25 October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): M. Pischiutta, F. Villani, S. D’Amico, M. Vassallo, F. Cara, D. Di Naccio, D. Farrugia, G. Di Giulio, S. Amoroso, L. Cantore, A. Mercuri, D. Famiani, P. Galea, A. Akinci, A. Rovelli
      We performed geophysical investigations in the northwestern sector of the island of Malta to reconstruct velocity-depth models and provide shear-wave velocity profiles. We have chosen two sites, one located in Rabat (Malta) and another in the Golden Bay area. We used both active (seismic and electrical 2D-tomography, Multichanel Analysis of Surface Waves – MASW) and passive (2D arrays and single-station measurements using ambient noise) geophysical methods. Consistently with previous studies performed in this part of Malta, we have found that both sites are characterised by site resonance in the frequency range 1-2 Hz as an effect of the local lithostratigraphic succession that shows an impedance contrast at about 60-90 m depth. This resonance effect can have important implications on both seismic hazard as well as seismic risk evaluation of the region since the amplified frequency range coincides with the resonance frequencies typical of 5–10 storey buildings which are very diffuse in the Maltese Islands, especially after intense recent urbanization. We also highlight the importance of performing seismic velocity measurements even at rock sites. As an example, the Golden Bay site would be classified as class “A” following the EuroCode EC8 when considering only the outcropping lithology represented by limestone rocks. Conversely the subsoil characterization provided by this study has revealed that this site falls in the EC8 class “B”, stressing the importance of direct geophysical measurements since the a-priori assignment to A-class could lead to wrong estimates in evaluating the site response.

      PubDate: 2016-10-30T14:59:47Z
      DOI: 10.1016/j.pce.2016.10.013
       
  • The Effects of Material Loading and Flow Rate on the Disinfection of
           Pathogenic Microorganisms Using Cation Resin-Silver Nanoparticle Filter
           System
    • Authors: L. Mpenyana-Monyatsi; N.H. Mthombeni; M.S. Onyango; M.N.B. Momba
      Abstract: Publication date: Available online 21 October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): L. Mpenyana-Monyatsi, N.H. Mthombeni, M.S. Onyango, M.N.B. Momba
      Waterborne diseases have a negative impact on public health in instances where the available drinking water is of a poor quality. Decentralised systems are needed to provide safe drinking water to rural communities. Therefore, the present study aimed to develop and investigate the point-of-use (POU) water treatment filter packed with resin-coated silver nanoparticles. The filter performance was evaluated by investigating the effects of various bed masses (10 g, 15 g, 20 g) and flow rates (2 mL/min, 5mL/min, 10 mL/min) by means of breakthrough curves for the removal efficiency of presumptive Escherichia coli, Shigella dysenteriae, Salmonella typhimurium and Vibrio cholerae from spiked groundwater samples. The results revealed that, as the bed mass increases the breakthrough time also increases with regards to all targeted microorganisms. However, when the flow rate increases the breakthrough time decreased. These tests demonstrated that resin-coated silver nanoparticle can be an effective material in removing all targeted microorganisms at 100 % removal efficiency before breakthrough points are achieved. Moreover the filter system demonstrated that it is capable of producing 15 L/day of treated water at an operating condition of 10 mL/min flow rate and 15g bed mass, which is sufficient to provide for seven individuals in the household if they consume 2 L/person/day for drinking purpose. Therefore, the bed mass of the filter system should be increased in order for it to produce sufficient water that will conform to the daily needs of an individual.

      PubDate: 2016-10-23T18:25:56Z
      DOI: 10.1016/j.pce.2016.10.012
       
  • Development of a Silicone-membrane Passive Sampler for Monitoring
           Cylindrospermopsin and Microcystin LR-YR-RR in Natural Waters
    • Authors: Hlengilizwe Nyoni; Bhekie B. Mamba; Titus A.M. Msagati
      Abstract: Publication date: Available online 21 October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Hlengilizwe Nyoni, Bhekie B. Mamba, Titus A.M. Msagati
      Silicone membrane tubes were functionalised by filling them with synthesised γ-Fe2O3 nanoparticles and used as a passive sampling device for monitoring microcystins and cylindrospermopsin in aquatic environments. This novel device was calibrated for the measurement of microcystin and cylindrospermopsin concentrations in water. The effect of temperature and hydrodynamics on the sampler performance was studied in a flow-through system under controlled conditions. The chemical uptake of microcystins (MCs) and cylindrospermopsin (CYN) into the passive sampler remained linear and integrative throughout the exposure period. The rate of accumulation of most of the MC compounds tested was dependent on temperature and flow velocity. The use of 13C labelled polychlorinated biphenyls as performance reference compounds (PRCs) in silicone membrane/γ-Fe2O3 nanoparticle passive sampler, Chemcatcher and polar organic chemical integrative sampler (POCIS) was evaluated. The majority of PRCs improved the semi quantitative nature of water concentration estimated by the three samplers. The corrected sampling rate values of model biotoxin compounds were used to estimate the time-weighted average concentrations in natural cyanobacterial water blooms of the Hartbeespoort dam. The corrected sampling rates R Scorr values varied from 0.1140 to 0.5628 Ld-1 between samplers with silicone membrane having the least R Scorr values compared to the Chemcatcher and POCIS. The three passive sampling devises provided a more relevant picture of the biotoxin concentration in the Hartbeespoort dam. The results suggested that the three sampling devices are suitable for use in monitoring microcystins and cylindrospermopsin concentrations in aquatic environments.

      PubDate: 2016-10-23T18:25:56Z
      DOI: 10.1016/j.pce.2016.10.010
       
  • Economic accounting of water: The Botswana experience
    • Authors: T. Setlhogile; J. Arntzen; O.B. Pule
      Abstract: Publication date: Available online 10 October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): T. Setlhogile, J. Arntzen, O.B. Pule
      Water accounts aim to capture the value of water resources and their use within the economy. The accounts complement the National Accounts as the latter's main indicator (GDP) does not reflect changes in natural capital. Botswana developed water accounts for the period 2010/11–2014/15 using the UN's standard System of Environmental Economic Accounting for water (SEEA-water). The article focuses both on the construction of physical flow accounts as well as on the policy implications for development planning and water resource management through the use of policy indicators. It also shows long-term trends in water abstraction and water use efficiency linking the SEEA water accounts with results of earlier (non-SEEA) water accounting projects in Botswana. The water accounts results show that water abstraction and consumption have been largely stable since 2010/11 despite population (1.9% p.a.) and economic growth (around 5% p.a.) likely due to a combination of water sector reforms and drought conditions in south eastern Botswana; the latter led to the drying up of several dams and the imposition of severe water restrictions. While public attention focuses mostly on water service providers, self-providers (mines and the agricultural sector) account for more than 50% of total water abstracted from the environment of water, demonstrating the need to pay more attention to self-providers in IWRM implementation. Water consumption is highest for the agricultural sector (70.2 Mm3) followed by households and mines at 41.2 and 39 Mm3 respectively in 2014/15. In terms of water use efficiency, value added per m3 has increased in time, showing (some) decoupling of water consumption and economic growth. This positive trend needs to be enhanced in the pursuit of economic diversification, which should focus on growth of water-efficient economic sectors. Finally, per capita water consumption has decreased over time; while this may indicate that people conserve water, it may also point at delivery problems associated with water sector reforms. This requires further analysis.

      PubDate: 2016-10-17T02:34:10Z
      DOI: 10.1016/j.pce.2016.10.007
       
  • Generation of climate change scenarios for precipitation and temperature
           at local scales using SDSM in Wami-Ruvu river basin Tanzania
    • Authors: Metekiya M. Gulacha; Deogratias M.M. Mulungu
      Abstract: Publication date: Available online 8 October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Metekiya M. Gulacha, Deogratias M.M. Mulungu
      The Wami-Ruvu River Basin is important for socio-economic activities in country such as water supply for Dar es Salaam and Morogoro cities, and major agricultural activities such as sugarcane irrigation at Mtibwa and Bagamoyo. Due to projected climate change and its impacts at global scale, it is important to understand future climate change impacts on water resources of Wami-Ruvu River basin. Rainfall and temeparature are key variables for analysis of water resources and were used in this study. The statistical downscaling model (SDSM) was used to downscale the coarse global circulation model (GCM) to local scales by involving predictor predictand relationship. The predictor variables were selected based on partial correlation value (partial r) and significance value (p-value). For assessment of climate change, the baseline period was 30 years during 1961-1990. The baseline period was partitioned into two periods for SDSM calibration and validation: 1961-1975 and 1976-1990 respectively. In this case, ground stations and the U.S. National Center for Environmental Prediction (NCEP) reanalysis atmospheric data were used. During validation, the inbuilt scenario generator was used to generate simulated time series for five stations: Morogoro Maji, Ulaya, Ukaguru, Morogoro Airport, Dodoma Airport and Ruvu at Morogoro Rd. Brd. For precipitation, the SDSM’s R2 (-) for the two periods ranged 0.07 - 0.20 and 0.21 - 0.63 respectively. The respective coefficient of correlation, r (-) ranged 0.03 - 0.05 and 0.46 - 0.80, indicating low to high performance of the SDSM. The respective R2 (-) values for temperature ranged: 0.42 – 0.5 and 0.6 – 0.98 respectively. The calibrated SDSM model was then used to downscale Global Circulation Model (GCM) scenario data to the local scales. The GCM used was HadCM3 where A2 and B2 scenarios were used. The climate change scenarios were determined using change factors. Results showed that for Wami-Ruvu basin the mean rainfall will change by -44-107%, -69-328% and 68-648% during 2020s, 2050s and 2080s for A2 scenario while by -37-117%, -56-199 and -76-346% respectively for B2 scenario as compared to the baseline period. In all cases, Ulaya and Morogoro Maji stations presented the lowest and highest extremes in the ranges. The downscaled and projected average monthly maximum temperature indicated increasing trend from 0.2 to 7.5 oC in 2020s to 2080s time period. The minimum temperature showed decreasing trend from -0.4 to -1.5oC during the same periods. These results indicate potential for floods or droughts occurrence in the basin, accordingly adaptation measures will be necessary.

      PubDate: 2016-10-10T01:55:52Z
      DOI: 10.1016/j.pce.2016.10.003
       
  • Assessing and mapping the severity of soil erosion using the 30-m Landsat
           multispectral satellite data in the former South African homelands of
           Transkei
    • Authors: Khoboso Seutloali; Timothy Dube; Onisimo Mutanga
      Abstract: Publication date: Available online 4 October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Khoboso Seutloali, Timothy Dube, Onisimo Mutanga
      Soil erosion is increasingly recognised as the principal cause of land degradation, loss of agricultural land area and siltation of surrounding water waterbodies. Accurate and up-to-date soil erosion mapping is key in understanding its severity if these negative impacts are to be minimised and affected areas rehabilitated. The aim of this work was to investigate map the severity of soil erosion, based on the 30-m Landsat series multispectral satellite data in the former South African homelands of Transkei between the year 1994 and 2010. Further, the study assessed if the observed soil erosion trends and morphology that existed in this area could be explained by biophysical factors (i.e. slope, stream erosivity, topographic wetness index) retrieved from the 30-m ASTER Digital Elevation Model (DEM). The results of this study indicate that the Transkei region experience varying erosion levels from moderate to very `severe. The large portion of the land area under the former homelands was largely affected by rill erosion with approximately 74% occurring in the year 1984 and 54% in 2010. The results also revealed specific thresholds of soil erosion drivers. These include steeper areas (≥30°), high stream power index greater than 2.0 (stream erosivity), relatively lower vegetation cover (≤15%) and low topographic wetness index (≤5%). The results of this work demonstrate the severity of soil erosion in the Southern African former homelands of Transkei for the year 1984 and 2010. Additionally, this work has demonstrated the significance of the 30-m Landsat multispectral sensor in examining soil erosion occurrence at a regional scale where in depth field work still remain a challenging task.

      PubDate: 2016-10-10T01:55:52Z
      DOI: 10.1016/j.pce.2016.10.001
       
  • Chitosan-based nanocomposites for de-nitrification of water
    • Authors: Monaheng L. Masheane; Lebea N. Nthunya; Soraya P. Malinga; Edward N. Nxumalo; Sabelo D. Mhlanga
      Abstract: Publication date: Available online 4 October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Monaheng L. Masheane, Lebea N. Nthunya, Soraya P. Malinga, Edward N. Nxumalo, Sabelo D. Mhlanga
      Novel chitosan (CTs) nanocomposite beads containing alumina (Al2O3, denoted as Al in the nanocomposites) and functionalized multiwalled carbon nanotubes (f-MWCNTs) (CTsAl/f-MWCNTs) were prepared using an environmentally benign phase inversion method and subsequently used for the removal of nitrates (NO3 -) in water. The ellipsoidal beads with an average size of 3 mm were readily formed at room temperature and contained a small amount of Al (20 wt%) and f-MWCNTs (5%). The beads were found to adsorb nitrates effectively over a wide range of pH (pH 2 – pH 6) and showed maximum nitrates removal of 96.8% from a 50 mg/L nitrate water solution. Pure CTs beads on the other hand removed only 23% at pH 4. Kinetic studies suggested that the particle diffusion was rate controlling step for the adsorption of nitrates on CTsAl/f-MWCNT nanocomposite beads. Langmuir-Freundlich isotherms revealed that the adsorption of nitrates was on the heterogeneous surface of CTsAl/f-MWCNT beads. The Dubinin–Radushkevich (D-R) isotherm further revealed that the adsorption of nitrates was by electrostatic interaction. Thermodynamic studies suggested that the adsorption was spontaneous and exothermic. More than 70% recovery was achieved for 5 cycles of desorption-degeneration studies. Al and f-MWCNTs have shown to improve swelling and solubility of CTs.

      PubDate: 2016-10-10T01:55:52Z
      DOI: 10.1016/j.pce.2016.10.004
       
  • Assessment of Drinking Water Quality and Rural Household Water Treatment
           in Balaka District, Malawi
    • Authors: Raphael C. Mkwate; Russel C.G. Chidya; Elijah M.M. Wanda
      Abstract: Publication date: Available online 6 October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Raphael C. Mkwate, Russel C.G. Chidya, Elijah M.M. Wanda
      Access to drinking water from unsafe sources is widespread amongst communities in rural areas such as Balaka District in Malawi. This situation puts many individuals and communities at risk of waterborne diseases despite some households adopting household water treatment to improve the quality of the water. However, there still remains data gaps regarding the quality of drinking water from such sources and the household water treatment methods used to improve public health. This study was, therefore, conducted to help bridge the knowledge gap by evaluating drinking water quality and adoption rate of household water treatment and storage (HWTS) practices in Nkaya, Balaka District. Water samples were collected from eleven systematically selected sites and analyzed for physico-chemical and microbiological parameters: pH, TDS, electrical conductivity (EC), turbidity, F-, Cl-, NO3 -, Na, K, Fe, Faecal Coliform (FC) and Faecal Streptococcus (FS) bacteria using standard methods. The mean results were compared to the World Health Organization (WHO) and Malawi Bureau of Standards (MBS) (MS 733:2005) to ascertain the water quality for drinking purposes. A total of 204 randomly selected households were interviewed to determine their access to drinking water, water quality perception and HWTS among others. The majority of households (72%, n=83) in Njerenje accessed water from shallow wells and rivers whilst in Phimbi boreholes were commonly used. The majority of household (>95%, n=204) were observed to be practicing HWST techniques by boiling or chlorination and water storage in closed containers. The levels of pH (7.10-7.64), F- (0.89-1.46 mg/L), Cl- (5.45-89.84 mg/L), NO3 - (0-0.16 mg/L), Na (20-490 mg/L), K (2.40-14 mg/L) and Fe (0.10-0.40 mg/L) for most sites were within the standard limits. The EC (358-2220 μS/cm), turbidity (0.54-14.60 NTU), FC (0-56 cfu/100 mL) and FS (0-120 cfu/100 mL) - mainly in shallow wells, were found to be above the WHO and MBS water quality specifications. The majority of the water samples (73%, n=11) were classified as of “Intermediate risk” (FC 11-100 cfu/100 mL), hence not suitable for human consumption without prior treatment. This calls for large scale adoption of HWTS and continued monitoring of the water sources used in the study areas.

      PubDate: 2016-10-10T01:55:52Z
      DOI: 10.1016/j.pce.2016.10.006
       
  • Managing water supply systems using free-market economy approaches: A
           detailed review of the implications for developing countries
    • Authors: C. Chikozho; K. Kujinga
      Abstract: Publication date: Available online 4 October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): C. Chikozho, K. Kujinga
      Decision makers in developing countries are often confronted by difficult choices regarding the selection and deployment of appropriate water supply governance regimes that sufficiently take into account national socio-economic and political realities. Indeed, scholars and practitioners alike continue to grapple with the need to create the optimum water supply and allocation decision-making space applicable to specific developing countries. In this paper, we review documented case studies from various parts of the world to explore the utility of free-market economics approaches in water supply governance. This is one of the major paradigms that have emerged in the face of enduring questions regarding how best to govern water supply systems in developing countries. In the paper, we postulate that increasing pressure on available natural resources may have already rendered obsolete some of the water supply governance regimes that have served human societies very well for many decades. Our main findings show that national and municipal water supply governance paradigms tend to change in tandem with emerging national development frameworks and priorities. While many developing countries have adopted water management and governance policy prescriptions from the international arena, national and local socio-economic and political realities ultimately determine what works and what does not work on the ground. We thus, conclude that the choice of what constitutes an appropriate water supply governance regime in context is never simple. Indeed, the majority of case studies reviewed in the paper tend to rely on a mix of market economics and developmental statism to make their water governance regimes more realistic and workable on the ground.

      PubDate: 2016-10-10T01:55:52Z
      DOI: 10.1016/j.pce.2016.10.002
       
  • Effect of monthly areal rainfall uncertainty on streamflow simulation
    • Authors: J.G. Ndiritu; N. Mkhize
      Abstract: Publication date: Available online 4 October 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): J.G. Ndiritu, N. Mkhize
      Areal rainfall is mostly obtained from point rainfall measurements that are sparsely located and several studies have shown that this results in large areal rainfall uncertainties at the daily time step. However, water resources assessment is often carried out a monthly time step and streamflow simulation is usually an essential component of this assessment. This study set out to quantify monthly areal rainfall uncertainties and assess their effect on streamflow simulation. This was achieved by; i) quantifying areal rainfall uncertainties and using these to generate stochastic monthly areal rainfalls, and ii) finding out how the quality of monthly streamflow simulation and streamflow variability change if stochastic areal rainfalls are used instead of historic areal rainfalls. Tests on monthly rainfall uncertainty were carried out using data from two South African catchments while streamflow simulation was confined to one of them. A non-parametric model that had been applied at a daily time step was used for stochastic areal rainfall generation and the Pitman catchment model calibrated using the SCE-UA optimizer was used for streamflow simulation. 100 randomly-initialised calibration-validation runs using 100 stochastic areal rainfalls were compared with 100 runs obtained using the single historic areal rainfall series. By using 4 rain gauges alternately to obtain areal rainfall, the resulting differences in areal rainfall averaged to 20% of the mean monthly areal rainfall and rainfall uncertainty was therefore highly significant. Pitman model simulations obtained coefficient of efficiencies averaging 0.66 and 0.64 in calibration and validation using historic rainfalls while the respective values using stochastic areal rainfalls were 0.59 and 0.57. Average bias was less than 5% in all cases. The streamflow ranges using historic rainfalls averaged to 29% of the mean naturalized flow in calibration and validation and the respective average ranges using stochastic monthly rainfalls were 86 and 90% of the mean naturalised streamflow. In calibration, 33% of the naturalized flow located within the streamflow ranges with historic rainfall simulations and using stochastic rainfalls increased this to 66%. In validation the respective percentages of naturalised flows located within the simulated streamflow ranges were 32 and 72% respectively. The analysis reveals that monthly areal rainfall uncertainty is significant and incorporating it into streamflow simulation would add validity to the results.

      PubDate: 2016-10-10T01:55:52Z
      DOI: 10.1016/j.pce.2016.10.005
       
  • Modelling analysis of water-use efficiency of Maize in Heihe river basin
    • Authors: Guofeng Wang; Jiancheng Chen; Qing Zhou; Xi Chu; Xiaoxue Zhou
      Abstract: Publication date: Available online 6 September 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Guofeng Wang, Jiancheng Chen, Qing Zhou, Xi Chu, Xiaoxue Zhou


      PubDate: 2016-09-08T13:56:03Z
      DOI: 10.1016/j.pce.2016.08.010
       
  • Water Ecological Function Zoning in Heihe River Basin, Northwest China
    • Authors: Dongdong Chen; Gui Jin; Qian Zhang; Aisha Olushola Arowolo; Yifan Li
      Abstract: Publication date: Available online 7 September 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Dongdong Chen, Gui Jin, Qian Zhang, Aisha Olushola Arowolo, Yifan Li
      Rapid urbanization coupled with increase in population growth rate in recent years has accelerated economic pressure on the ecological environment leading to a gradual deterioration of global and regional environment. This has particularly resulted into water contamination and shortage of water resources thus posing a great threat to human survival. How to guaranteeing sustainable use of basin water resources has attracted more and more attentions. The Heihe River Basin is the secondary longest river inland China and the significantly water source of Hexi Corridor, the problem of water pollution, ecological environment deterioration and the shortage of water has seriously threatened the ecological system of the Heihe River Basin. In this study, through depicting the characteristics of natural environment, human activities, water ecosystem services and other factors in Heihe River Basin we delineated the water ecological function in Heihe River using the principal components analysis and the K-means clustering method. In the study, Heihe river Basin is divided into 3 primary level areas and 8 secondary level sub-areas. Water ecological characteristics analysis showed that the spatial distribution of the water ecological function of Heihe River Basin was not uniform, which are mainly showed in three aspects, function of windproof and sand fixation, function of soil erosion prevention and function of water sources conservation. The results of this study can provide effective and scientific theoretical references for the integrated water sources management and the ecological function optimization of the Heihe River Basin.

      PubDate: 2016-09-08T13:56:03Z
      DOI: 10.1016/j.pce.2016.08.005
       
  • A Method to Correct Eddy Covariance Flux Underestimates under an Advective
           Environment for Arid or Semi-arid Regions
    • Authors: Hongbo Su; Yongmin Yang; Lina Xu; José L. Chávez; Steven R. Evett; Terry A. Howell; Jing Tian; Shaohui Chen; Jinyan Zhan
      Abstract: Publication date: Available online 31 August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Hongbo Su, Yongmin Yang, Lina Xu, José L. Chávez, Steven R. Evett, Terry A. Howell, Jing Tian, Shaohui Chen, Jinyan Zhan
      Water scarcity is one of the main factors limiting agricultural development in arid or semi-arid areas. Accurate Evapotranspiration (ET) observations and estimations are crucial in water cycle studies to estimate water losses from the terrestrial surfaces to the atmosphere to close the regional water budget. The eddy covariance (EC) method is an important technique measure ET and other land surface energy fluxes. However, the underestimation of energy fluxes and the problem of EC energy balance non-closure are far from solved. In this study, a new method is proposed to account for advection in order to correct EC data under advective environments. This advection based method was applied to data from Bushland, TX, which is subject to dry air and strong winds. Observations from two identical EC systems as well as two precision monolithic weighing lysimeters were used in this analysis. Both EC sites showed significant underestimates of evapotranspiration (ET) compared with lysimeter measurements. The daily energy balance closure for NE01 and SE02 sites were 0.78 and 0.74 respectively. The advection correction method provided improved performance in daytime, and it is more suitable for ET estimate than forcing closure under the advective environment. For nighttime, two methods (NCM1 and NCM2) were proposed to correct EC underestimates. Finally, all the corrected ET values were compared with the lysimeter measurements. For NE01 site, the MAD (mean absolute deviation) and the RMSD (root mean square deviation) were 47.72 W/m2 and 67.66 W/m2, respectively; and the r2 (coefficient of determination) was 0.85. For SE02 site, the MAD and RMSD were 30.59 W/m2 and 44.43 W/m2; and the r2 was 0.93. The statistical measures illustrated that the proposed methods are functional and appropriate under an advective environment. The accurate estimate of actual evapotranspiration will benefit both the strategic planning of optimal water uses and the improved understanding the environmental and hydrological processes.

      PubDate: 2016-09-03T13:21:07Z
      DOI: 10.1016/j.pce.2016.08.009
       
  • The 24 May 2014 (Mw6.8) earthquake (North Aegean Trough): spatiotemporal
           evolution, source and slip model from teleseismic data
    • Authors: Anastasia Kiratzi; Eva Tsakiroudi; Christoforos Benetatos; George Karakaisis
      Abstract: Publication date: Available online 28 August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Anastasia Kiratzi, Eva Tsakiroudi, Christoforos Benetatos, George Karakaisis
      We use teleseismic data to calculate the source model of the 24 May 2014 earthquake and regional catalogues to examine the spatial-temporal characteristics of the sequence. The sequence started in Saros Basin but almost simultaneously aftershocks spread along a ∼200 km zone, activating the entire North Aegean Trough. The aftershock sequence was rich in moderate (M<4) size events, but very deficient in strong events – only two Mw4.9 aftershocks-a characteristic observed in previous sequences in the region. The teleseismic waveforms were best fit by two sub-events, which were lagged by 18s in time and by a 50 km jump in space, along the same fault line. The centroid depth of the first sub-event is 22km, at the base of the lower crust, and for the second is 14 km. The resolved total source time function is ∼30s. The finite-fault slip model is characterized by an asymmetric bilateral rupture propagation, to the west and east of the hypocentre. The major slip is confined downdip from the hypocentre, within the deeper 12-25km part. This deep slip migrated updip from the hypocentre to form the second slip patch, in the eastward segment. In all our models the maximum dislocation was of the order of 1m. For our preferred model parametrization, the rupture speed is 3km/s, and the scalar moment equal to 1.76×1019 Nm (Mw6.8). This earthquake highlighted the fact that strike-slip faulting in the North Aegean Sea, can attain large lengths and activate very wide zones, reaching densely populated regions.

      PubDate: 2016-08-29T12:34:54Z
      DOI: 10.1016/j.pce.2016.08.003
       
  • Forecast and optimal allocation of production, living and ecology water
           consumption in Zhangye, China
    • Authors: Qian Xu; Wei Song; Ying Zhang
      Abstract: Publication date: Available online 6 August 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Qian Xu, Wei Song, Ying Zhang
      The water crisis is one of three crises that are persecuting the world. China is among the countries that face severe water shortages. Water scarcity and water pollution have seriously affected China's sustainable development in terms of the economy and society. Water resources per capita of China is only one quarter of the world's average. In addition, about 70 percent of China’s rivers, lakes, and reservoirs are affected by pollution. Due to limited water resources, a crucial issue for the sustainable development of the watershed is how to resolve the human/nature competition for water and how to achieve the coordinated development of the economy, society and ecology. On the basis of defining water consumption for production, living and ecology (WPLE), this paper proposes a framework for forecasting and optimally allocating WPLE. Using Zhangye, in the middle reaches of the Heihe River Basin as the case study area, we forecasted and optimally allocated WPLE under three development scenarios, i.e. the conventional development scenario (CDS), the economy-priority development scenario (EPDS) and the environmentally sustainable development scenario (ESDS). In 2010, the proportions of WPLE in Zhangye were 87.73%, 2.74% and 9.53%, respectively. In 2020, the proportions of WPLE will be 74.80%, 4.50% and 20.70% under the CDS, 76.16%, 5.27% and 18.57% under the EPDS, and 74.99%, 4.51% and 20.50% under the ESDS. In the future, the proportion of production water consumption of Zhangye will drastically decrease, while the proportion of ecological water consumption will significantly increase. The main contradiction of the co-evolution of WPLE of Zhangye is the competitiveness of production and living water consumption with ecological water consumption.

      PubDate: 2016-08-10T11:13:00Z
      DOI: 10.1016/j.pce.2016.07.003
       
 
 
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