for Journals by Title or ISSN
for Articles by Keywords
help
  Subjects -> PHYSICS (Total: 798 journals)
    - ELECTRICITY AND MAGNETISM (9 journals)
    - MECHANICS (20 journals)
    - NUCLEAR PHYSICS (49 journals)
    - OPTICS (88 journals)
    - PHYSICS (579 journals)
    - SOUND (22 journals)
    - THERMODYNAMICS (31 journals)

PHYSICS (579 journals)

The end of the list has been reached or no journals were found for your choice.
Journal Cover Physics and Chemistry of the Earth, Parts A/B/C
  [SJR: 0.624]   [H-I: 42]   [2 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1474-7065
   Published by Elsevier Homepage  [2970 journals]
  • Effect of iron salt counter ion in dose–response curves for
           inactivation of Fusarium solani in water through solar driven Fenton-like
           processes
    • Abstract: Publication date: February 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 91
      Author(s): Verónica Aurioles-López, M. Inmaculada Polo-López, Pilar Fernández-Ibáñez, Aurelio López-Malo, Erick R. Bandala
      The inactivation of Fusarium solani in water was assessed by solar driven Fenton-like processes using three different iron salts: ferric acetylacetonate (Fe(acac)3), ferric chloride (FeCl3) and ferrous sulfate (FeSO4). The experimental conditions tested were [Fe] ≈ 5 mg L−1, [H2O2] ≈ 10 mg L−1 and [Fe] ≈ 10 mg L−1; [H2O2] ≈ 20 mg L−1 mild and high, respectively, and pH 3.0 and 5.0, under solar radiation. The highest inactivation rates were observed at high reaction conditions for the three iron salts tested at pH 5.0 with less than 3.0 kJ L−1 of accumulate energy (Q UV ) to achieve over 99.9% of F. solani inactivation. Fe(acac)3 was the best iron salt to accomplishing F. solani inactivation. The modified Fermi equation was used to fix the experimental inactivation, data showed it was helpful for modeling the process, adequately describing dose–response curves. Inactivation process using FeSO4 at pH 3.0 was modeled fairly with r 2  = 0.98 and 0.99 (mild and high concentration, respectively). Fe(acac)3, FeCl3 and FeSO4 at high concentration (i.e. [Fe] ≈ 10 mg L−1; [H2O2] ≈ 20 mg L−1) and pH 5.0 showed the highest fitting values (r 2  = 0.99). Iron salt type showed a remarkable influence on the Fenton-like inactivation process.


      PubDate: 2016-04-24T13:42:01Z
       
  • Possible climate change evidence in ten Mexican watersheds
    • Abstract: Publication date: February 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 91
      Author(s): Efrain Mateos, Julio-Sergio Santana, Martin J. Montero-Martínez, Alejandro Deeb, Alfred Grunwaldt
      This paper suggests possible evidence of climate change in Mexico at the watershed level, based solely on historical data. The official Mexican climate dataset was used to find the best set of stations for each watershed. Maximum and minimum temperatures and rainfall in ten watersheds are analyzed from 1970 to 2009. Maximum temperature trends show a significant increment in most of these watersheds. Furthermore, Daily Temperature Range (DTR) exhibits a positive trend (increments), thus implying an increase in temperature extremes. This study also shows that the difference between maximum and minimum monthly temperature trends is negatively correlated with monthly precipitation trends. As a result, land-use and land-cover changes could be the main drivers of climate change in the region.


      PubDate: 2016-04-24T13:42:01Z
       
  • Temperature and heat wave trends in northwest Mexico
    • Abstract: Publication date: February 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 91
      Author(s): Polioptro F. Martínez-Austria, Erick R. Bandala, Carlos Patiño-Gómez
      Increase in temperature extremes is one of the main expected impacts of climate change, as well as one of the first signs of its occurrence. Nevertheless, results emerging from General Circulation Models, while sufficient for large scales, are not enough for forecasting local trends and, hence, the IPCC has called for local studies based on on-site data. Indeed, it is expected that climate extremes will be detected much earlier than changes in climate averages. Heat waves are among the most important and least studied climate extremes, however its occurrence has been only barely studied and even its very definition remains controversial. This paper discusses the observed changes in temperature trends and heat waves in Northwestern Mexico, one of the most vulnerable regions of the country. The climate records in two locations of the region are analyzed, including one of the cities with extreme climate in Mexico, Mexicali City in the state of Baja California and the Yaqui River basin at Sonora State using three different methodologies. Results showed clear trends on temperature increase and occurrence of heat waves in both of the study zones using the three methodologies proposed. As result, some policy making suggestion are included in order to increase the adaptability of the studied regions to climate change, particularly related with heat wave occurrence.


      PubDate: 2016-04-24T13:42:01Z
       
  • Climate threats, water supply vulnerability and the risk of a water crisis
           in the Monterrey Metropolitan Area (Northeastern Mexico)
    • Abstract: Publication date: February 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 91
      Author(s): Nicholas P. Sisto, Aldo I. Ramírez, Ismael Aguilar-Barajas, Víctor Magaña-Rueda
      This paper evaluates the risk of a water crisis – a substantial, sudden reduction in water supply – in the Monterrey Metropolitan Area (MMA), posed by climate threats and the vulnerability of its water supply system. Our analysis of long-term precipitation, water supply and water availability data reveals that the MMA is highly vulnerable to recurring periods of exceptionally low precipitation and scarce surface water availability. We identify two episodes in the recent past (1998 and 2013) when the MMA water supply system almost collapsed as reservoirs neared depletion in the face of abnormally dry weather. Furthermore our climate projections point to warmer and drier future conditions for the region and consequently, heightened climate threats. We conclude that the risk of a water crisis in the MMA is substantial and probably will increase due to climate change. This establishes a clear and pressing need for a comprehensive package of adaptation measures to mitigate the consequences of a water crisis should one occur as well as to reduce the likelihood of such an event.


      PubDate: 2016-04-24T13:42:01Z
       
  • Appropriate technology and climate change adaptation
    • Abstract: Publication date: February 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C, Volume 91
      Author(s): Erick R. Bandala, Carlos Patiño-Gomez



      PubDate: 2016-04-24T13:42:01Z
       
  • A new approach for computing a flood vulnerability index using cluster
           analysis
    • Abstract: Publication date: Available online 22 April 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Paulo Fernandez, Sandra Mourato, Madalena Moreira, Luísa Pereira
      A Flood Vulnerability Index (FloodVI) was developed using Principal Component Analysis (PCA) and a new aggregation method based on Cluster Analysis (CA). PCA simplifies a large number of variables into a few uncorrelated factors representing the social, economic, physical and environmental dimensions of vulnerability. CA groups areas that have the same characteristics in terms of vulnerability into vulnerability classes. The grouping of the areas determines their classification contrary to other aggregation methods in which the areas’ classification determines their grouping. While other aggregation methods distribute the areas into classes, in an artificial manner, by imposing a certain probability for an area to belong to a certain class, as determined by the assumption that the aggregation measure used is normally distributed, CA does not constrain the distribution of the areas by the classes. FloodVI was designed at the neighbourhood level and was applied to the Portuguese municipality of Vila Nova de Gaia where several flood events have taken place in the recent past. The FloodVI sensitivity was assessed using three different aggregation methods: the sum of component scores, the first component score and the weighted sum of component scores. The results highlight the sensitivity of the FloodVI to different aggregation methods. Both sum of component scores and weighted sum of component scores have shown similar results. The first component score aggregation method classifies almost all areas as having medium vulnerability and finally the results obtained using the CA show a distinct differentiation of the vulnerability where hot spots can be clearly identified. The information provided by records of previous flood events corroborate the results obtained with CA, because the inundated areas with greater damages are those that are identified as high and very high vulnerability areas by CA. This supports the fact that CA provides a reliable FloodVI.


      PubDate: 2016-04-24T13:42:01Z
       
  • Assessing the feasibility of integrating remote sensing and in-situ
           
    • Abstract: Publication date: Available online 22 April 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): S. Dlamini, I. Nhapi, W. Gumindoga, T. Nhiwatiwa, T. Dube
      This work investigates the likelihood of integrating the cheap and readily-available broadband multispectral MODIS data and in-situ measurements in quantifying and monitoring water quality status of an inland lake within Upper Manyame Catchment in Zimbabwe. Specifically we used MODIS images to quantify inland lake chlorophyll_a concentrations, as a proxy for predicting lake pollution levels. The findings of this study show a high chlorophyll_a concentration of 0.101±0.128 μg/L within the Lake. The results further demonstrated that the chlorophyll_a concentration levels did not significantly vary (p = 0.788) between sites, except among depths (p=0.05). Further, prediction results based on the relationship between observed and predicted chlorophyll_a produced a high R2 value of 0.89 and a root mean square error (RMSE) value of 0.003 μg/L. Moreover, the derived landuse maps of Upper Manyame Catchment indicated a significant variation in the percentage settlement in 1985, 1994 and 2010 change from 1985 to 2010. For instance, 8% increase in settlement in the period between 1994 and 2010 and over 12% increase from 1985 to 2010 and a decline in percent forest coverage (i.e. 9.8% in 1985 to 2.0% in the year 2010) in the catchment was observed. Overall, the findings of this study highlights the importance of free and readily-available satellite datasets (such as the multispectral MODIS and Landsat) in quantifying and monitoring water quality across inland lakes especially in data-scarce areas like Sub-Saharan Africa.


      PubDate: 2016-04-24T13:42:01Z
       
  • The Typical Seismic Behavior in the Vicinity of a Large Earthquake
    • Abstract: Publication date: Available online 22 April 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      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 1,000) 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: 2016-04-24T13:42:01Z
       
  • Anomalous behavior of ionospheric parameters above the Kamchatka peninsula
           before and during seismic activity
    • Abstract: Publication date: Available online 24 April 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Vadim V. Bogdanov, Aleksandr V. Kaisin, Aleksey V. Pavlov, Anastasia L. Polyukhova, Claudia-Veronika Meister
      In the present work, searching for new methods of earthquake prediction, variations of ionospheric plasma parameters and ionospheric turbulence before and during seismic activity are studied applying complex radiophysical methods and a theoretical probabilistic approach. The analysis of radiophysical observations of some seismic events of February-March (28.02.–02.03.) 2013 shows, that K-layer formation (appearance of a corpuscular layer due to precipitation of particles from the radiation belts), E s - and F-spread effects as well as an increase of the critical f o F2-frequency occurred about one day before earthquakes with a magnitude M≥6.5. F2-spread was even observed at low geomagnetic activity. One seismic shock was preceded by an abnormal increase in the value of the critical frequency f o F2, and about two hours after the shock, f o F2 was again well below the median value although a geomagnetic storm happened. Therefore, it may be concluded that, in future, variations of ionospheric plasma parameters and turbulence may be used as additional tool to determine the magnitude of preparing strong earthquakes. The propabilistic method which is applied in the present work is already described in (Bogdanov et al., J. Volcanology and Seismology, 4(6), 412–422, 2010). It allowed to detect a growth of seismic activity in the Kamchatka region in 2013.


      PubDate: 2016-04-24T13:42:01Z
       
  • High resolution WRF climatic simulations for the Iberian Peninsula: Model
           validation
    • Abstract: Publication date: Available online 22 March 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Martinho Marta-Almeida, João C. Teixeira, Maria João Carvalho, Paulo Melo-Gonçalves, Alfredo M. Rocha
      A high resolution atmospheric modelling study was done for a 20-year recent historical period. The dynamic downscaling approach adopted used the Max Planck Institute Earth System Model (MPI-ESM) to drive the WRF running in climate mode. Three online nested domains were used covering part of the North Atlantic and Europe, with a resolution 81 km, and reaching 9 km in the innermost domain which covers the Iberian Peninsula. This paper presents the validation of the WRF configuration, which is based on historic simulations between 1986 and 2005 and observational datasets of near surface temperature and precipitation for the same period. The validation was done in terms of comparison of probability distributions between model results and observations, as daily climatologies, spatially averaged inside subdomains obtained with cluster analysis of the observations, for each of the four seasons. In addition, Taylor diagrams are presented for each of the seasons and subdomains. This validation approach was repeated with the results of a new WRF simulation with the same parameterisations but forced by the ERA-Interim reanalysis. The capacity of the MPI-ESM driven WRF configuration to compare with observations and in a manner similar to the ERA-Interim driven WRF, ensures the capacity of the configuration for climate and climate change studies. Considering the difficulty to simulate extremes in long term simulations, the results showed a comfortable comparison of both models (forced by climate model and reanalysis results) with observations. This provides us confidence on the continuity of using the MPI-ESM driven WRF configuration for climate studies.


      PubDate: 2016-03-25T19:31:49Z
       
  • Critical Pollution levels in Umguza River, Zimbabwe
    • Abstract: Publication date: Available online 21 March 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): A. Chinyama, R. Ncube, W. Ela
      In most countries worldwide regulatory bodies set effluent discharge limits into rivers and other natural water bodies. These limits specify the maximum permissible concentration of defined pollutants that may be discharged into the water body. This limit is conceptually based on the self-purification (assimilative) capacity of the receiving water. However, this self-purification constant is itself a function of the water’s pollutant loading. Umguza River situated south west of Zimbabwe, is fed by tributaries that drain an urban catchment and as such is prone to pollution due to human activities in the catchment. This study investigated the levels of pollution in Umguza River that would affect its self-purification capacity. This was achieved by characterising the spatial distribution of a selected range of water quality parameters as well as determining the self-purification capacity of a stretch of the river. Critical pollutant concentrations were determined for some of the parameters that showed high values along the stretch. The selected parameters of interest were dissolved oxygen, suspended solids, phosphates, nitrates, COD, turbidity, ammonia, pH, alkalinity and temperature. The study was carried out from January 2014 to April 2014. The self-purification capacity was determined using a formula that compares the mass flux of a pollutant upstream and downstream of the selected stretch of the river. Statistical analysis was used to establish relationships between the pollutants and the self-purification capacity of the river. The study found that the levels of ammonia and phosphates were very high compared to the regulated limits (2mg/l vs 0.5mg/l; and 8mg/l vs 0.5mg/l respectively). It was also found that the self-purification capacity varied significantly across pollutants. It was therefore concluded that a critical pollutant concentration exists above which the river completely loses its natural ability to assimilate and decrease its pollutant load over time. It was also concluded that the self-purification capacity depends on the pollutant of concern in the river. It is recommended that the self-purification capacity of a river be determined before regulatory bodies set effluent discharge limits. It is also recommended that the water quality of water bodies draining pollution prone catchments be monitored regularly, besides just monitoring the discharge points.


      PubDate: 2016-03-25T19:31:49Z
       
  • Climate Change induced by Southern Hemisphere Desertification
    • Abstract: Publication date: Available online 21 March 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Ye Wang, Xiaodong Yan
      Some 10 to 20% of global dry-lands are already degraded, and the ongoing desertification threatens the world’s poorest populations. Studies on desertification effects are essential for humans to adapt to the environmental challenges posed by desertification. Given the importance of the much larger southern ocean to the global climate and the Southern Hemisphere (SH) climate changes in phase with those in the north, the biogeophysical effects of the SH desertification on climate are assessed using an Earth system model of intermediate complexity, MPM-2. This analysis focuses on differences in climate among the averages of simulations with desert expansion in different latitude bands by year 2000. The localized desertification causes significant global changes in temperature and precipitation as well as surface albedo. On the global scale, cooling dominates the SH desertification effects. However, the biogeophysical effects are most significant in regions with desertification, and the cooling is also prominent in northern mid-latitudes. Desert expansion in 15°-30°S reveals statistically most significant cooling and increased precipitation over the forcing regions during spring. The global and regional scale responses from desertification imply the climate teleconnection and address the importance of the effects from the SH which are contingent on the location of the forcing. Our study indicates that biogeophysical mechanisms of land cover changes in the SH need to be accounted for in the assessment of land management options especially for latitude band over 15°-30°S.


      PubDate: 2016-03-25T19:31:49Z
       
  • The effect of roughness in simultaneously retrieval of land surface
           parameters
    • Abstract: Publication date: Available online 21 March 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Mina Moradizadeh, Mohammad R. Saradjian
      Using remotely-sensed data, various soil moisture estimation models have been developed for bare soil areas. Previous studies have shown that the brightness temperature (BT) measured by passive microwave sensors were affected by characteristics of the land surface parameters including soil moisture, vegetation cover and soil roughness. Therefore knowledge of vegetation cover and soil roughness is important for obtaining frequent and global estimations of land surface parameters especially soil moisture. In this study, a model called Simultaneous Land Parameters Retrieval Model (SLPRM) that is an iterative least-squares minimization method is proposed. The algorithm estimates surface soil moisture, land surface temperature and canopy temperature simultaneously in vegetated areas using AMSR-E (Advance Microwave Scanning Radiometer-EOS) brightness temperature data. The simultaneous estimations of the three parameters are based on a multi-parameter inversion algorithm which includes model construction, calibration and validation using observations carried out for the SMEX03 (Soil Moisture Experiment 2003) region in the South and North of Oklahoma. Roughness parameter has also been included in the algorithm to increase the soil parameters retrieval accuracy. Unlike other methods, the SLPRM method works efficiently in all land covers types. The study focuses on soil parameters estimation by comparing three different scenarios with the inclusion of roughness data and selects the most appropriate one. The difference between the resulted accuracies of scenarios is due to the roughness calculation approach. The analysis on the retrieval model shows a meaningful and acceptable accuracy on soil moisture estimation according to the three scenarios. The SLPRM method has shown better performance when the SAR (Synthetic Aperture RADAR) data are used for roughness calculation.


      PubDate: 2016-03-25T19:31:49Z
       
  • Determination of background concentrations of hydrochemical parameters and
           water quality assessment in the Akhuryan River Basin (Armenia)
    • Abstract: Publication date: Available online 21 March 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Hovhannisyan Arpine, Shahnazaryan Gayane
      The determination of background values of hydrochemical parameters, to distinguish between natural concentration and anthropogenically-influenced concentrations, is highly relevant. In presented study, to estimate the background values of hydrochemical parameters in Akhuryan River Basin, log-normal probability functions on the hydrochemical parameters concentrations was applied. The study is carried out on the basis of hydrochemical data of surface water quality monitoring for the period of 2010-2013. This study highlights the usefulness of application of site-specific background concentrations for the evaluation, interpretation of surface water quality and for determination of pollution sources.


      PubDate: 2016-03-25T19:31:49Z
       
  • Evaluation of Borehole Water Quality in Rural-Areas Of Northern Malawi:
           Case of Zombwe in Mzimba
    • Abstract: Publication date: Available online 22 March 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): O. Nakoma, R.C.G. Chidya, S. Matamula, C.B.J. Chawinga
      Many people in developing countries in Sub-Saharan region generally rely on groundwater sources for potable water. Despite increased demand for safe drinking water over the years, its availability, quality, and supply remains a challenge in Malawi and other developing countries. This study was conducted to evaluate quality of water from boreholes (n=20) in Zombwe Extension Planning Area (EPA), Mzimba in Northern Malawi to ascertain their safety. Desktop studies and participatory approaches were employed to assess the socio-economic activities and water supply regime in the study areas. Water samples were analyzed for selected physico-chemical parameters: pH, conductivity (EC), turbidity, water temperature, nitrate ( NO 3 − ), magnesium (Mg), calcium (Ca), zinc (Zn), fluoride (F-), and sulphate ( SO 4 2 − ). In-situ and laboratory analyses were carried out using portable meters and standard procedures. The results were compared with national standards (Malawi Bureau of Standards - MBS) for boreholes and shallow well water quality and international standards (World Health Organization - WHO) for drinking water. The following ranges were obtained for all the sites: pH (6.00-7.80), EC (437-3128 μS/cm), turbidity (0.10-5.80 NTU), water temperature (27.0-30.60 °C), NO 3 − (0.30-30.00 mg/L), F- (0.10-8.10 mg/L), Mg (31.00-91.00 mg/L), Ca (20.00-197.10 mg/L), SO 4 2 − (10.20-190 mg/L), Fe (0.10-3.60 mg/L) and Zn (0.00-5.10 mg/L). In general, several sites (>80%, n=20) complied with both MBS and WHO limits. No significant differences (p>0.05) was observed for most parameters (>65%, n=11). Generally, levels of groundwater pollution were not significant in the area despite some parameters such as Ca and SO 4 2 − showing higher levels at other sites. The study area registered groundwater sources with very hard water (244.60-757.80 mg/L CaCO3) suggesting contamination of groundwater probably due to mineralization influenced by underground rock material. Further studies are needed to ascertain the groundwater quality and health effects of microbiological and other parameters in the area. There is also a need for regular monitoring of the water sources for comparative analyses and spatio-temporal variation assessment.


      PubDate: 2016-03-25T19:31:49Z
       
  • On the spatial distribution of seismicity and the 3D tectonic stress field
           in western Greece
    • Abstract: Publication date: Available online 23 March 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      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, N-S 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: 2016-03-25T19:31:49Z
       
  • Application of satellite products and hydrological modeling for flood
           early warning
    • Abstract: Publication date: Available online 19 March 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Sifan A. Koriche, Tom H.M. Rientjes
      Floods have caused devastating impacts to the environment and society in Awash River Basin, Ethiopia. Since flooding events are frequent, this marks the need to develop tools for flood early warning. In this study, we propose a satellite based flood index to identify the runoff source areas that largely contribute to extreme runoff production and floods in the basin. Satellite based products used for development of the flood index are CMORPH (0.250 by 0.250, daily) product for calculation of the Standard Precipitation Index (SPI) and a SRTM digital elevation model for calculation of the Topographic Wetness Index (TWI). Other satellite products used in this study are for rainfall-runoff modelling to represent rainfall, potential evapotranspiration, vegetation cover and topography. Results of the study show that assessment of spatial and temporal rainfall variability by satellite products may well serve in flood early warning. Preliminary findings on effectiveness of the flood index developed in this study indicate that the index is well suited for flood early warning. The index combines SPI and TWI, and preliminary results illustrate the spatial distribution of likely runoff source areas that cause floods in flood prone areas.


      PubDate: 2016-03-20T19:09:57Z
       
  • Micrometeorological Measurements and Vapour Pressure Deficit Relations
           under In-field Rainwater Harvesting
    • Abstract: Publication date: Available online 10 March 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Weldemichael A. Tesfuhuney, Sue Walker, Leon D. Van Rensburg, A. Stephan Steyn
      In a cropped field, microclimate and thermal stability conditions depend on the canopy structures and the prevailing weather. The main aim of the study therefore was to characterize the vertical profiles of weather variables within and above a maize (Zea mays L.) canopy and to describe the water vapour pressure deficit (VPD) under different atmospheric and soil surface conditions for both wide and narrow runoff strips with the in-field rainwater harvesting (IRWH) system. Micrometeorological measurements of wind, temperature and relative humidity were performed at eight levels, within canopy (1.8 and 2.1 m), and just above the canopy (2.4, 2.7, 3.0, and 3.3 m) up to reference levels (3.9 and 4.5 m) when the maize reached a maximum height of 2.2 m. Under incomplete canopy cover of the IRWH system, two important factors complicated evapotranspiration estimation, namely the local advection and high temperatures of the bare soil between adjacent plant rows. Diurnal variations of water vapour related to turbulence at each locality and its position in the thermal internal boundary layers. Generally, advection was more pronounced in wide runoff strips than narrow strips. On wide runoff strips the wind was more effective in replacing the air between the rows and maintained a higher driving force for evaporation. The maximum VPD over the narrow strips was observed at reference level during a dry day, at about 2.2 kPa in the afternoon, while wet day VPD reached a maximum of 1.8 kPa. The VPD of the wide runoff strips correlated negatively with wind speed, but showed a fairly positive correlation with some scattered values on wet days after rain. Therefore, profile characteristics within and above plant canopies played a key role in determining the VPD and consequently, could help to explain transpiration rates of crops. Hence, VPD relations enhanced the understanding of the heat energy exchange processes under the heterogeneous nature of maize canopy of the IRWH tillage system.


      PubDate: 2016-03-11T18:23:31Z
       
  • The hydrology of sand rivers in Zimbabwe and the use of remote sensing to
           assess their level of saturation
    • Abstract: Publication date: Available online 10 March 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): S.C. Mpala, A.S. Gagnon, M.G. Mansell, S.W. Hussey
      Sand rivers are ephemeral watercourses containing sand that are occasionally flooded with rainwater runoff during the rainy season. Although the riverbed appears dry for most of the year, there is perennial groundwater flow within the sand. This water flowing beneath the surface is a valuable resource for local communities; nonetheless our understanding of such river systems is limited. Hence, this paper aims to improve our understanding of the hydrology of sand rivers and to examine the potential use of remote sensing to detect the presence of water in the sand. The relationship between rainfall events and changes in the water level of two sand rivers in the Matabeleland South Province of Zimbabwe was investigated. A lagged relationship was observed for the Manzamnyama River but for the Shashani River the relationship was seen only when considering cumulative rainfall events. The comparison of the modelled flow as simulated by a water balance model with observations revealed the important influence of the effective sediment depth on the recharge and recession of the alluvial channels in addition to the length of the channel. The possibility of detecting water in the alluvial sands was investigated using remote sensing. During the wet season, optical images showed that the presence of water on the riverbed was associated with a smooth signal, as it tends to reflect the incident radiation. A chronological analysis of radar images for different months of the year demonstrates that it is possible to detect the presence of water in the sand rivers. These results are a first step towards the development of a methodology that would aim to use remote sensing to help reducing survey costs by guiding exploratory activities to areas showing signs of water abstraction potential.


      PubDate: 2016-03-11T18:23:31Z
       
  • How is water availability related to the land use and morphology of an
           inland valley wetland in Kenya?
    • Abstract: Publication date: Available online 10 March 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Beate Böhme, Mathias Becker, Bernd Diekkrüger, Gerd Förch
      Small inland valley wetlands contribute substantially to the livelihoods of rural communities in East Africa. Their conversion into farmland is driven by water availability. We quantified spatial-temporal dynamics of water availability in a headwater wetland in the humid zone of Kenya. Climatic conditions, soil moisture contents, groundwater levels and discharge data were monitored. A land-use map and a digital elevation model of the valley bottom were created to relate variations in soil moisture to dominant land uses and valley morphology. Upland crops occupied about a third of the wetland area, while approximately a quarter of the wet, central part of the valley bottom was designated for flood-tolerant taro, grown either by itself or in association or in rotation with upland crops. Finally, natural vegetation was found in 3% of the mapped area, mainly in sections with nearpermanent soil saturation. The HBV rainfall-runoff model's overestimation of stream discharge during the long dry season of the hydrological year 2010/2011 can be explained by the strong seasonal impact of water abstraction on the wetland's water balance. Our study vividly demonstrates the necessity of multi-method approaches for assessing the impact of management practices on water availability in valley bottom wetlands in East Africa.


      PubDate: 2016-03-11T18:23:31Z
       
  • Land use/land cover change and implications for ecosystems services in the
           Likangala River Catchment, Malawi
    • Abstract: Publication date: Available online 10 March 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Deepa Pullanikkatil, Lobina G. Palamuleni, Tabukeli M. Ruhiiga
      Likangala River catchment in Zomba District of Southern Malawi is important for water resources, agriculture and provides many ecosystem services. Provisioning ecosystem services accrued by the populations within the catchment include water, fish, medicinal plants and timber among others. In spite of its importance, the River catchment is under threat from anthropogenic activities and land use change. This paper studies land uses and land cover change in the catchment and how the changes have impacted on the ecosystem services. Landsat 5 and 8 images (1984, 1994, 2005 and 2013) were used to map land cover change and subsequent inventorying of provisioning ecosystem services. Participatory Geographic Information Systems and Focus group discussions were conducted to identify provisioning ecosystems services that communities benefit from the catchment and indicate these on the map. Post classification comparisons indicate that since 1984, there has been a decline in woodlands from 135.3km2 in 1984 to 15.5km2 in 2013 while urban areas increased from 9.8km2 to 23.8km2 in 2013. Communities indicated that provisioning ecosystems services such as forest products, wild animals and fruits and medicinal plants have been declining over the years. In addition, evidence of catchment degradation through waste disposal, illegal sand mining, deforestation and farming on marginal lands were observed. Population growth, urbanization and demand for agricultural lands have contributed to this land use and land cover change. The study suggests addressing catchment degradation through integrated method where an ecosystems approach is used. Thus, both the proximate and underlying driving factors of land-use and land cover change need to be addressed in order to sustainably reduce ecosystem degradation.


      PubDate: 2016-03-11T18:23:31Z
       
  • Water supply dynamics and quality of alternative water sources in
           low-income areas of Lilongwe City, Malawi
    • Abstract: Publication date: Available online 10 March 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Russel C.G. Chidya, Wapulumuka O. Mulwafu, S. Banda
      Recent studies in many developing countries have shown the emergence of Small Scale Independent Providers (SSIPs) in low-income areas (LIAs) as practical alternatives to water utilities. This study explored supply dynamics and quality of alternative water sources in four LIAs of Lilongwe City in Malawi using qualitative and quantitative methods. Household-level surveys (n=120) and transect walks were employed to determine the socio-economic activities in the areas. One-on-one discussions were made with water source owners (SSIPs) (n=24). Data on policy and institutional frameworks was collected through desktop study and Key Informant Interviews (n=25). Quality of the water sources (shallow wells and boreholes) was determined by collecting grab samples (n=24) in triplicate using 500 mL bottles. Selected physico-chemical and microbiological parameters were measured: pH, EC, TDS, turbidity, water temperature, salinity, K, Na, Ca, Mg, Cl-, F-, NO3 -, alkalinity, water hardness, Feacal coliform (FC) and Faecal Streptococci (FS) bacteria. Water quality data was compared with Malawi Bureau of Standards (MBS) and World Health Organization (WHO) guidelines for drinking water. Shallow wells were reported (65%, n=120) to be the main source of water for household use in all areas. Some policies like prohibition of boreholes and shallow wells in City locations were in conflict with other provisions of water supply, sanitation and housing. High levels of FC (0-2100 cfu/100 mL) and FS (0-1490 cfu/100 mL) at several sites (>90%, n=24) suggest water contamination likely to impact on human health. This calls for upgrading and recognition of the water sources for improved water service delivery.


      PubDate: 2016-03-11T18:23:31Z
       
  • From standard to fractional structural visco-elastodynamics: Application
           to seismic site response
    • Abstract: Publication date: Available online 12 February 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): C. Germoso, A. Fraile, E. Alarcon, J.V. Aguado, F. Chinesta
      This paper revisits viscoelastodynamics from its most standard formulation to some more advanced description involving frequency-dependent damping (or viscosity), analyzing the effects of considering fractional derivatives for representing such viscous contributions. We will prove that such a choice results in richer models that can accommodate different constraints related to the dissipated power, response amplitude and phase angle. Moreover, the use of fractional derivatives allows to accommodate in parallel, within a generalized Kelvin-Voigt analog, many dashpots that contribute to increase the modeling flexibility for describing experimental findings. Finally, the effect of fractional damping in dynamic soil models will be addressed within a seismic site analyses framework.


      PubDate: 2016-02-15T12:10:32Z
       
  • Moment tensors, state of stress and their relation to faulting processes
           in Gujarat, Western India
    • Abstract: Publication date: Available online 3 February 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      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 2001 MW 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: 2016-02-10T12:08:43Z
       
  • Analysis of the 2012–2013 Torreperogil-Sabiote seismic swarm
    • Abstract: Publication date: Available online 3 February 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      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: 2016-02-10T12:08:43Z
       
  • On the relationship between atmospheric water vapour transport and
           extra-tropical cyclones development
    • Abstract: Publication date: Available online 3 February 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Juan A. Ferreira, Margarida L.R. Liberato, Alexandre M. Ramos
      In this study we seek to investigate the role of atmospheric water vapour on the intensification of extra-tropical cyclones over the North Atlantic Ocean and more specifically to investigate the linkage between atmospheric rivers’ conditions leading to the explosive development of extra-tropical cyclones. Several WRF-ARW simulations for three recent extra-tropical storms that had major negative socio-economic impacts in the Iberian Peninsula and south-western Europe (Klaus, 2009; Gong, 2013 and Stephanie, 2014) are performed in which the water vapour content of the initial and boundary conditions are tuned. Analyses of the vertically integrated vapour transport show the dependence of the storms’ development with atmospheric water vapour. In addition, results also show changes in the shape of the jet stream resulting in a reduction of the upper wind divergence, which in turn affects the intensification of the extra-tropical cyclones studied. This study suggests that atmospheric rivers tend to favour the conditions for explosive extra-tropical storms’ development in the three case studies, as simulations performed without the existence of atmospheric rivers produce shallow mid-latitudes cyclones, that is, cyclones that are not so intense as those on the reference simulations.


      PubDate: 2016-02-10T12:08:43Z
       
  • Seismic Moment Tensor Inversion Using 3D Velocity Model and Its
           Application to the 2013 Lushan Earthquake Sequence
    • Abstract: Publication date: Available online 4 February 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      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: 2016-02-10T12:08:43Z
       
  • Degradation of organic matter from wastewater using advanced primary
           treatment by O3 and O3/UV in a pilot plant
    • Abstract: Publication date: Available online 23 January 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Yaneth Bustos-Terrones, Jesús Gabriel Rangel-Peraza, Antonio Sanhouse, Erick R. Bandala, Luis G. Torres
      The oxidation of organic matter from wastewater using ozone, ultraviolet radiation and ozone/UV oxidation was evaluated in a pilot plant, applying a continuous effluent arising from the Autonomous Metropolitan University wastewater treatment plant. The oxidation was measured as the efficiency to remove organic load, measured as chemical oxygen demand. The use of ozone and UV was evaluated separately and in combination through a continuous process. Three different ozone doses (0.6 to 1.2 mg O3/L) and three different UV radiation fluencies (6.7 to 20.12 mJ/cm2) were assessed. A synergistic effect of the combined process ozone/UV was demonstrated, and a maximal chemical oxygen demand reduction was achieved both processes. Due to residence times used (less than 1 min), 36% of chemical oxygen demand reduction was obtained when ozone treatment was evaluate separately and only 9% using ultraviolet radiation.


      PubDate: 2016-01-25T11:18:14Z
       
  • Estimation of Groundwater Vulnerability to Pollution based on DRASTIC in
           the Niipele sub-Basin of the Cuvelai Etosha Basin, Namibia
    • Abstract: Publication date: Available online 23 January 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): J.T. Hamutoko, H. Wanke, H.J. Voigt
      Surface water is a scarce resource in Namibia with about sixty percent of Namibia’s population dependent on groundwater for drinking purposes. With increasing population, the country faces water challenges and thus groundwater resources need to be managed properly. One important aspect of Integrated Water Resources Management is the protection of water resources, including protection of groundwater from contamination and over-exploitation. This study explores vulnerability mapping as a basic tool for protecting groundwater resources from pollution. It estimates groundwater vulnerability to pollution in the upper Niipele sub-basin of the Cuvelai-Etosha in Northern Namibia using the DRASTIC index. The DRASTIC index uses GIS to estimate groundwater vulnerability by overlaying different spatially referenced hydrogeological parameters that affect groundwater contamination. The study assesses the discontinuous perched aquifer (KDP) and the Ohangwena multi-layered aquifer 1 (KOH-1). For perched aquifers, point data was regionalized by a hydrotope approach whereas for KOH-1 aquifer, inverse distance weighting was used. The hydrotope approach categorized different parts of the hydrogeological system with similar properties into five hydrotopes. The result suggests that the discontinuous perched aquifers are more vulnerable than Ohangwena multi-layered aquifer 1. This implies that vulnerability increases with decreasing depth to water table because contaminants have short travel time to reach the aquifer when they are introduced on land surface. The nitrate concentration ranges between 2 to 288 mg/l in perched aquifers while in Ohangwena multi-layered aquifer 1, it ranges between 1 to 133 mg/l. It was observed that perched aquifers have high nitrate concentrations than Ohangwena 1 aquifer, which correlates well with the vulnerability results.


      PubDate: 2016-01-25T11:18:14Z
       
  • Knowledge and Practices regarding Water, Sanitation and Hygiene (WASH)
           among mothers of under-fives in Mawabeni rural area, Zimbabwe
    • Abstract: Publication date: Available online 9 January 2016
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Tendai Demberere, Tayedza Chidziya, Tatenda Ncozana, Norman Manyeruke
      The research study sought to assess knowledge and practices of mothers of under-fives regarding WASH in Mawabeni communal area in Zimbabwe. Focus group discussions, interviews, questionnaires and observation checklists were used to collect data. Data was analysed by developing specific themes related to the objectives and then frequencies were computed in Microsoft Excel. The mean score on WASH knowledge for the mothers of under-fives according to the Knowledge Index was 1. Knowledge regarding safety of water from different sources was generally poor with 70% of the mothers regarding water from surface sources to be safe to drink without treatment. Use of wide mouthed containers without lids was also common in the study area. However, no relationship was established between the type of water container used and the socio-demographic characteristics of the respondents. Knowledge regarding the importance of ablutions was generally good as highlighted by 78% of the mothers who regarded latrines as being important in prevention and control of diseases as well as for hygiene purposes. However, latrine ownership was noted to be related to the income level of the household (p < 0.0001). A total of 57% of the mothers had good knowledge on hand washing, indicating that it helped to prevent diseases. Generally, knowledge levels and sanitation practices on WASH among mothers of under-fives in Mawabeni were both poor and this could be a contributory factor to the high incidence of diarrheal diseases for under-fives in the area.


      PubDate: 2016-01-12T10:18:40Z
       
  • Recent trends of extreme temperature indices for the Iberian Peninsula
    • Abstract: Publication date: Available online 30 December 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): D. Fonseca, M.J. Carvalho, M. Marta-Almeida, P. Melo-Gonçalves, A. Rocha
      Climate change and extreme climate events have a significant impact on societies and ecosystems. As a result, climate change projections, especially related with extreme temperature events, have gained increasing importance due to their impacts on the well-being of the population and ecosystems. However, most studies in the field are based on coarse global climate models (GCMs). In this study, we perform a high resolution downscaling simulation to evaluate recent trends of extreme temperature indices. The model used was Weather Research and Forecast (WRF) forced by MPI-ESM-LR, which has been shown to be one of the more robust models to simulate European climate. The domain used in the simulations includes the Iberian Peninsula and the simulation covers the 1986 − 2005 period (i.e. recent past). In order to study extreme temperature events, trends were computed using the Theil-Sen method for a set of temperature indexes defined by the Expert Team on Climate Change Detection and Indices (ETCCDI). For this, daily values of minimum and maximum temperatures were used. The trends of the indexes were computed for annual and seasonal values and the Mann-Kendall Trend test was used to evaluate their statistical significance. In order to validate the results, a second simulation, in which WRF was forced by ERA-Interim, was performed. The results suggest an increase in the number of warm days and warm nights, especially during summer and negative trends for cold nights and cold days for the summer and spring. For the winter, contrary to the expected, the results suggest an increase in cold days and cold nights (warming hiatus). This behavior is supported by the WRF simulation forced by ERA-Interim for the autumn days, pointing to an extension of the warming hiatus phenomenon to the remaining seasons. These results should be used with caution since the period used to calculate the trends may not be long enough for this purpose. However, the general sign of trends are similar for both simulations despite some differences in their magnitudes.


      PubDate: 2015-12-31T11:29:33Z
       
  • Land use mapping from CBERS-2 images with open source tools by applying
           different classification algorithms
    • Abstract: Publication date: Available online 29 December 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Antonio J. Sanhouse-Garcia, Jesús Gabriel Rangel-Peraza, Yaneth Bustos-Terrones, Alfonso García-Ferrer, Francisco J. Mesas-Carrascosa
      Land cover classification is often based on different characteristics between their classes, but with great homogeneity within each one of them. This cover is obtained through field work or by mean of processing satellite images. Field work involves high costs; therefore, digital image processing techniques have become an important alternative to perform this task. However, in some developing countries and particularly in Casacoima municipality in Venezuela, there is a lack of geographic information systems due to the lack of updated information and high costs in software license acquisition. This research proposes a low cost methodology to develop thematic mapping of local land use and types of coverage in areas with scarce resources. Thematic mapping was developed from CBERS-2 images and spatial information available on the network using open source tools. The supervised classification method per pixel and per region was applied using different classification algorithms and comparing them among themselves. Classification method per pixel was based on Maxver algorithms (maximum likelihood) and Euclidean distance (minimum distance), while per region classification was based on the Bhattacharya algorithm. Satisfactory results were obtained from per region classification, where overall reliability of 83.93 % and kappa index of 0.81 % were observed. Maxver algorithm showed a reliability value of 73.36% and kappa index 0.69%, while Euclidean distance obtained values of 67.17% and 0.61% for reliability and kappa index, respectively. It was demonstrated that the proposed methodology was very useful in cartographic processing and updating, which in turn serve as a support to develop management plans and land management. Hence, open source tools showed to be an economically viable alternative not only for forestry organizations, but for the general public, allowing them to develop projects in economically depressed and/or environmentally threatened areas.


      PubDate: 2015-12-31T11:29:33Z
       
  • Influence of Deposition of Fine Plant Debris in River Floodplain Shrubs on
           Flood Flow Conditions - the Warta River Case Study
    • Abstract: Publication date: Available online 21 December 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Robert Mazur, Tomasz Kałuża, Joanna Chmist, Natalia Walczak, Ireneusz Laks, Paweł Strzeliński
      This paper presents problems caused by organic material transported by flowing water. This material is usually referred to as plant debris or organic debris. Its composition depends on the characteristic of the watercourse. For lowland rivers, the share of the so-called small organic matter in plant debris is considerable. This includes both various parts of water plants and floodplain vegetation (leaves, stems, blades of grass, twigs, etc.). During floods, larger woody debris poses a significant risk to bridges or other water engineering structures. It may cause river jams and may lead to damming of the flowing water. This, in turn, affects flood safety and increases flood risk in river valleys, both directly and indirectly. The importance of fine plant debris for the phenomenon being studied comes down to the hydrodynamic aspect (plant elements carried by water end up on trees and shrubs, increase hydraulic flow resistance and contribute to the nature of flow through vegetated areas changed from micro-to macro-structural). The key part of the research problem under analysis was to determine qualitative and quantitative debris parameters and to establish the relationship between the type of debris and the type of land use of river valleys (crop fields, meadows and forested river sections). Another problem was to identify parameters of plant debris for various flow conditions (e.g. for low, medium and flood flows). The research also included an analysis of the materials deposited on the structure of shrubs under flood flow conditions during the 2010 flood on the Warta River.


      PubDate: 2015-12-23T11:00:19Z
       
  • State of Tectonic Stress in Shillong Plateau of Northeast India
    • Abstract: Publication date: Available online 23 December 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      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: 2015-12-23T11:00:19Z
       
  • QLg tomography in Gujarat, Western India
    • Abstract: Publication date: Available online 23 December 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Sandeep Kumar Aggarwal, Prosanta Kumar Khan
      We propose a novel Lg attenuation tomography model (QLg tomography) for the state of Gujarat, Western India, using earthquake data recorded by the Gujarat Seismic Network, operated by the Institute of Seismological Research in Gandhinagar. The waveform dataset consist of 400 3-component recordings, produced by 60 earthquakes with magnitude (ML) spanning from 3.6 to 5.1, recorded at 60 seismic stations having epicentral distances spanning between 200 and 500 km. Spectral amplitude decays for Lg wave displacement were obtained by generalized inversion at 17 frequencies spanning between 0.9 and 9 Hz. Lg wave propagation efficiency was measured by Lg/Pn spectral ratio categorizing as efficient ratio ≥ 6 for 86%, intermediate ratio of 3 to 6 for 10% and inefficient ratio < 3 for 4% paths of total 400 ray paths. The earthquake size and quality of waveform recorded at dense network found sufficient to resolve lateral variation of QLg in Gujarat. Average power-law attenuation relationship obtained for Gujarat as QLg(f) = 234f0.64, which corresponds to high attenuation in comparison to peninsular India shield region and other several regions around the world. QLg tomography resolves the highly attenuating crust of extremely fractured Saurashtra region and tectonically active Kachchh region. The Gujarat average attenuation is also lying in between them. The low attenuation in Cambay and Narmada rift basins and extremely low attenuation in patch of Surendranagar area is identified. This study is the first attempt and can be utilized as pivotal criteria for scenario hazard assessment, as maximum hazard has been reported in highly attenuating tectonically active Kachchh region and in low attenuating Cambay, Narmada and Surendranagar regions. The site and source terms are also obtained along with the QLg inversion. The estimated site responses are comparable with observed local geological condition and agree with the previously reported site amplifications at the same sites. The source terms are comparable with local magnitude estimated from Network. The Mw (Lg) is nearly equivalent to ML (GSN) and the slight differences are noted for larger magnitude events.


      PubDate: 2015-12-23T11:00:19Z
       
  • Nanosized iron based permeable reactive barriers for nitrate removal
           – Systematic review
    • Abstract: Publication date: Available online 15 December 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Rui Araújo, Ana C. Meira Castro, João Santos Baptista, António Fiúza
      It is unquestionable that an effective decision concerning the usage of a certain environmental clean-up technology should be conveniently supported. Significant amount of scientific work focusing on the reduction of nitrate concentration in drinking water by both metallic iron and nanomaterials and their usage in permeable reactive barriers has been worldwide published over the last two decades. This work aims to present in a systematic review of the most relevant research done on the removal of nitrate from groundwater using nanosized iron based permeable reactive barriers. The research was based on scientific papers published between 2004 and June 2014. It was performed using 16 combinations of keywords in 34 databases, according to PRISMA statement guidelines. Independent reviewers validated the selection criteria. From the 4161 records filtered, 45 met the selection criteria and were selected to be included in in this review. This study’s outcomes show that the permeable reactive barriers are, indeed, a suitable technology for denitrification and with good performance record but the long-term impact of the use of nanosized zero valent iron in this remediation process, in both on the environment and on the human health, is far to be conveniently known. As a consequence, further work is required on this matter, so that nanosized iron based permeable reactive barriers for the removal of nitrate from drinking water can be genuinely considered an eco-efficient technology.


      PubDate: 2015-12-19T10:10:01Z
       
  • An exploratory study of spatial annual maximum of monthly precipitation in
           the northern region of Portugal
    • Abstract: Publication date: Available online 15 December 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): D.P. Gomes, M.M. Neves, E. Moreira
      Adequately analyzing and modeling the extreme rainfall events is of great importance because of the effects that their magnitude and frequency can have on human life, agricultural productivity and economic aspects, among others. A single extreme event may affect several locations, and their spatial dependence has to be appropriately taken into account. Classical geostatistics is a well-developed field for dealing with location referenced data, but it is largely based on Gaussian processes and distributions, that are not appropriate for extremes. In this paper, an exploratory study of the annual maximum of monthly precipitation recorded in the northern area of Portugal from 1941-2006 at 32 locations is performed. The aim of this paper is to apply max-stable processes, a natural extension of multivariate extremes to the spatial set-up, to briefly describe the models considered and to estimate the required parameters to simulate prediction maps.


      PubDate: 2015-12-15T09:57:35Z
       
  • A dependence modelling study of extreme rainfall in Madeira Island
    • Abstract: Publication date: Available online 2 December 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Délia Gouveia-Reis, Luiz Guerreiro Lopes, Sandra Mendonça
      The dependence between variables plays a central role in multivariate extremes. In this paper, spatial dependence of Madeira Island’s rainfall data is addressed within an extreme value copula approach through an analysis of maximum annual data. The impact of altitude, slope orientation, distance between rain gauge stations and distance from the stations to the sea are investigated for two different periods of time. The results obtained highlight the influence of the island’s complex topography on the spatial distribution of extreme rainfall in Madeira Island.


      PubDate: 2015-12-06T09:04:17Z
       
  • Identification of nitrate sources in groundwater and potential impact on
           drinking water reservoir (Goczałkowice reservoir, Poland)
    • Abstract: Publication date: Available online 30 November 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Joanna Czekaj, Sabina Jakóbczyk – Karpierz, Hanna Rubin, Sławomir Sitek, Andrzej J. Witkowski
      Goczałkowice dammed reservoir (area - 26 km2) is a strategic object for flood control in the Upper Vistula River catchment and one of the most important source of drinking water in the Upper Silesian Industrial Region (Southern Poland). Main aims of the investigation were identification of sources of nitrate and assessment of their significance in potential risk to groundwater quality. In the catchment area monitoring network of 22 piezometers, included 14 nested, have been installed. The significant spatial and seasonal differences in chemical composition between northern and southern part of the catchment were indicated based on the groundwater sampling conducted twice - in autumn 2011 and spring 2012. Maximum observed concentrations of nitrate were identified in northern part of the study area 255 mg/L as a results of inappropriate sewage management and agriculture activity. Results, based on the combines multi-scale hydrogeological and hydrochemical field studies, groundwater flow and transport modelling, dual stable isotope approach and geochemical modelling indicate mainly agriculture and inappropriate sewage water management as a sources of NO3 - contamination of groundwater which moreover is affected by geochemical processes. In general, contaminated groundwater does not impact surface water quality. However, due to high concentration of nitrate in northern part a continues measurements of nitrogen compounds should be continued and used for reducing uncertainty of the predictive scenarios of the mass transport modelling in the study area.


      PubDate: 2015-12-01T18:42:23Z
       
  • Water quality monitoring in the Paul do Boquilobo Biosphere Reserve
    • Abstract: Publication date: Available online 30 November 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): C. Baptista, L. Santos
      The Paul do Boquilobo is an important wetland ecosystem classified by Unesco as a MAB Biosphere reserve also awarded Ramsar site status, representing one of the most important habitats for the resident nesting colony of Cattle Egret (Bulbucus ibis). Yet owing to its location, it suffers from human induced impacts which include industrial and domestic effluent discharges as well as agricultural land use which have negatively impacted water quality. The current study reports the results obtained from the introductory monitoring programme of surface water quality in the Nature Reserve to emphasize the detrimental impact of the anthropogenic activities in the water quality of such an important ecosystem. The study involved physicochemical and biotic variables, microbial parameters and biological indicators. Results after 3 years of monitoring bring to evidence a poor water quality further impaired by seasonal patterns. Statistical analysis of data attributed water quality variation to 3 main parameters - pH, dissolved oxygen and nitrates, indicating heavy contamination loads from both organic and agricultural sources. Seasonality plays a role in water flow and climatic conditions, where sampling sites presented variable water quality data, suggesting a depurative function of the wetland.


      PubDate: 2015-12-01T18:42:23Z
       
  • Timescale Differences between SC-PDSI and SPEI for Drought Monitoring in
           China
    • Abstract: Publication date: Available online 19 November 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Haiyan Zhao, Ge Gao, Wei An, Xukai Zou, Haitao Li, Meiting Hou
      The Palmer Drought Severity Index (PDSI) has been widely used to monitor drought. Its characteristics are more suitable for measuring droughts of longer timescales, and this fact has not received much attention. The Standardized Precipitation Evapotranspiration Index (SPEI) can better reflect the climatic water balance, owing to its combination of precipitation and potential evapotranspiration. In this study, we selected monthly average air temperature and precipitation data from 589 meteorological stations of China's National Meteorological Information Center, to compare the effects of applying a self-calibrating PDSI (SC-PDSI) and SPEI to monitor drought events in the station regions, with a special focus on differences of event timescale. The results show the following. 1) Comparative analysis using SC-PDSI and SPEI for drought years and characters of three dry periods from 1961–2011 in the Beijing region showed that durations of SC-PDSI-based dry spells were longer than those of 3-month and 6-month SPEIs, but equal to those of 12-month or longer timescale SPEIs. 2) For monitoring evolution of the fall 2009 to spring 2010 Southwest China drought and spring 2000 Huang-Huai drought, 3-month SPEI could better monitor the initiation, aggravation, alleviation and relief of drought in the two regions, whereas the SC-PDSI was insensitive to drought recovery because of its long-term memory of previous climate conditions. 3) Analysis of the relationship between SC-PDSI for different regions and SPEI for different timescales showed that correlation of the two indexes changed with region, and SC-PDSI was maximally correlated with SPEI of 9–19 months in China. Therefore, SC-PDSI is only suitable for monitoring mid- and long-term droughts, owing to the strong lagged autocorrelation such as 0.4786 for 12-month lagged ones in Beijing, whereas SPEI is suitable for both short- and long-term drought-monitoring and should have greater application prospects in China.


      PubDate: 2015-11-22T17:42:46Z
       
  • Assessment of the effectiveness of combined adsorption and photocatalysis
           for removal of the herbicide isoproturon
    • Abstract: Publication date: Available online 14 November 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Martín M. Dávila-Jiménez, María P. Elizalde-González, Esmeralda García-Díaz, Alba M. Santes-Aquino
      The aim of this research was to decompose isoproturon and adsorb its photoproducts by developing a carbon material from a juice industry waste. Carbon-TiO2 hybrid materials were obtained by impregnating carbonized guava seeds with TiO2 gels prepared from TiOSO4⋅xH2O and NH4OH using glycerol as a binder and thermally treating the materials at 500°C. Raman studies confirmed the anatase phase of TiO2. SEM images showed isolated TiO2 agglomerates firmly attached to the carbon surface. The adsorption behavior of isoproturon on guava carbon was studied and yielded S-type adsorption isotherms. The photocatalytic activities of the prepared hybrid materials were monitored to study the kinetics and elimination process both of the herbicide and its photoproducts. The reaction was monitored by UV–Vis spectrophotometry, LC-DAD and LC-MS, enabling identification of some intermediate species. Among the photoproducts produced by carbon-TiO2 hybrid materials, amino-isopropylphenol was detected.
      Graphical abstract image

      PubDate: 2015-11-18T17:26:06Z
       
  • Cloning and expression of vgb gene in Bacillus cereus, improve phenol and
           p-nitrophenol biodegradation
    • Abstract: Publication date: Available online 11 November 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Angel Eduardo Vélez-Lee, Felipe Cordova-Lozano, Erick R. Bandala, Jose Luis Sanchez-Salas
      In this work, the vgb gene from Vitrocilla stercoraria was used to genetically modify a Bacillus cereus strain isolated from pulp and paper wastewater effluent. The gene was cloned in a multicopy plasmid (pUB110) or uni-copy gene using a chromosome integrative vector (pTrpBG1). B. cereus and its recombinant strains were used for phenol and p-nitrophenol biodegradation using aerobic or micro-aerobic conditions and two different temperatures (i.e. 37 and 25°C). Complete (100%) phenol degradation was obtained for the strain where the multicopy of vgb gene was present, 98% for the strain where uni-copy gene was present and 45% for wild type strain for the same experimental conditions (i.e. 37°C and aerobic condition). For p-nitrophenol degradation at the same conditions, the strain with the multi-copy vgb gene was capable to achieve 50% of biodegradation, ∼100% biodegradation was obtained using the uni-copy strain and ∼24% for wild type strain. When the micro-aerobic condition were tested, the biodegradation yield showed a significant decreased. The biodegradation trend observed for aerobic was similar for micro-aerobic assessments: the modified strains showed higher degradation rates when compared with wild type strain. For all experimental conditions, the highest p-nitrophenol degradation was observed using the strain with uni-copy of vgb gene. Besides the increase of biodegradative capability of the strain, insertion of the vgb gene was observed able to modify other morphological characteristics such as avoiding the typical flake formation in the B. cereus culture. In both cases, the modification seems to be related with the enhancement of oxygen supply to the cells generated by the vgb gene insertion. The application of the genetically modified microorganism (GMM) to the biodegradation of pollutants in contaminated water possess high potential as an environmentally friendly technology to facing this emergent problem.


      PubDate: 2015-11-14T17:09:46Z
       
  • Dry spells assessment with reference to the maize crop in the Luvuvhu
           River catchment of South Africa
    • Abstract: Publication date: Available online 11 November 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Teboho Elisa Masupha, Mokhele Edmond Moeletsi, Mitsuru Tsubo
      Agricultural productivity in South Africa is negatively affected by drought as a result of frequent periodic dry spells and increasing crop water demands resulting in poor crop development and low yields. Thus, we embarked on this study which aims at investigating dry spell occurrences in relation to growing season of maize in the Luvuvhu River Catchment. Daily rainfall data (1945-2014) from 12 stations which represent the catchment fairly well was utilized in this study. Three consecutive planting dates were staggered based on three consecutive onsets of the rainy season. Dry spells were categorized into three groups: short, medium and long dry spells. The data was then subjected to theoretical distribution fitting using the Anderson-Darling goodness-of-fit test; and probabilities of occurrence were computed using a probabilistic model that best fits the data. Trend analysis was performed on the frequency of dry spells per growing period using the non-parametric Spearman’s rank correlation test. Out results indicated high probabilities (≥80%) of short dry spells at all the stations irrespective of the timing of planting. Further analysis revealed that a risk of yield reduction with planting following the first onset of rains was higher than that with planting following the second and third onsets. In order to minimize this risk, farmers can be advised to plant between mid-November to mid-December. Trend analysis indicated no trend for all the various dry spell lengths except for Thohoyandou with a decreasing trend and Sigonde with a weak increasing trend in long dry spells. Such findings can be used to describe drought conditions for improvement of agricultural productivity and food security, in a given area.


      PubDate: 2015-11-14T17:09:46Z
       
  • Joint Venture Schemes in Limpopo Province and their outcomes on
           smallholder farmers Livelihoods
    • Abstract: Publication date: Available online 11 November 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Everisto Mapedza, Barbara van Koppen, Pinimidzai Sithole, Magalie Bourblanc
      Joint Venture schemes based on the floppy irrigation technology are being promoted in the post-Apartheid South Africa’s Limpopo Province. Access to land and water resources in South Africa are largely viewed as a mechanism for re-dressing the Apartheid injustices. This research was part of a broader applied research to help inform irrigation practise in the Limpopo Province. The research used literature review, key informant interviews and a questionnaire survey. The overall research question sought to understand how the Joint Venture Schemes had benefited the smallholder farmers. This paper argues that the joint venture partnership created a new injustice. Firstly, the Joint Venture Scheme design is fundamentally a bad idea which disempower farmers not only to water access but also land as well. The choice of the 'efficient' floppy irrigation technology was made by the state and entailed that land had to be managed as a single unit. In order to make more effective use of this highly sophisticated new technology, the smallholder farmers also needed to go into a joint venture partnership with a white commercial farmer. By virtue of signing the Joint Venture agreement the farmers were also forfeiting their land and water rights to be used for crop production. The smallholder farmers lost access to their water and land resources and were largely relegated to sharing profits – when they exist - with hardly any skills development despite what was initially envisaged in the Joint Venture partnership. Secondly, the implementation of the JVS has been skewed from the start which explains the bad results. This paper further shows how the negative outcomes affected women in particular. As the smallholder farmers argue the technological options chosen by the state have excluded both male and female farmers from accessing and utilising their land and water resources in order to improve their livelihoods; it has entrenched the role of the state and the private interests at the expense of the smallholder male and female farmers in whose name the irrigation funding was justified. The paper concludes by offering recommendations on how joint venture schemes can be genuinely participatory and meaningfully address the rural livelihoods.


      PubDate: 2015-11-14T17:09:46Z
       
  • Oil refinery wastewater treatment using coupled electrocoagulation and
           fixed film biological processes
    • Abstract: Publication date: Available online 11 November 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Laura S. Pérez, Oscar M. Rodriguez, Silvia Reyna, José Luis Sánchez-Salas, J. Daniel Lozada, Marco A. Quiroz, Erick R. Bandala
      Oil refinery wastewater was treated using a coupled treatment process including electrocoagulation (EC) and a fixed film aerobic bioreactor. Different variables were tested to identify the best conditions using this procedure. After EC, the effluent was treated in an aerobic biofilter. EC was capable to remove over 88% of the overall chemical oxygen demand (COD) in the wastewater under the best working conditions (6.5 V, 0.1 M NaCl, 4 electrodes without initial pH adjustment) with total petroleum hydrocarbon (TPH) removal slightly higher than 80%. Aluminum release from the electrodes to the wastewater was found an important factor for the EC efficiency and closely related with several operational factors. Application of EC allowed to increase the biodegradability of the sample from 0.015, rated as non-biodegradable, up to 0.5 widely considered as biodegradable. The effluent was further treated using an aerobic biofilter inoculated with a bacterial consortium including gram positive and gram negative strains and tested for COD and TPH removal from the EC treated effluent during 30 days. Cell count showed the typical bacteria growth starting at day three and increasing up to a maximum after eight days. After day eight, cell growth showed a plateau which agreed with the highest decrease on contaminant concentration. Final TPHs concentration was found about 600 mgL-1 after 30 days whereas COD concentration after biological treatment was as low as 933 mgL-1. The coupled EC-aerobic biofilter was capable to remove up to 98% of the total TPH amount and over 95% of the COD load in the oil refinery wastewater.


      PubDate: 2015-11-14T17:09:46Z
       
  • SPI drought class prediction using log-linear models applied to wet and
           dry seasons
    • Abstract: Publication date: Available online 11 November 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): Elsa E. Moreira
      A log-linear modelling for 3-dimensional contingency tables was used with categorical time series of SPI drought class transitions for prediction of monthly drought severity. Standardized Precipitation Index (SPI) time series in 12- and 6-month time scales were computed for 10 precipitation time series relative to GPCC datasets with 2.5 degrees spatial resolution located over Portugal and with 112 years length (1902 to 2014). The aim was modelling two-month step class transitions for the wet and dry seasons of the year and then obtain probability ratios – Odds – as well as their respective confidence intervals to estimate how probable a transition is compared to another. The prediction results produced by the modelling applied to wet and dry season separately, for the 6- and the 12-month SPI time scale, were compared with the results produced by the same modelling without the split, using skill scores computed for the entire time series length. Results point to good prediction performances ranging from 70-80% in the percentage of corrects (PC) and 50-70% in the Heidke skill score (HSS), with the highest scores obtained when the modelling is applied to the SPI12. The adding up of the wet and dry seasons introduced in the modelling brought improvements in the predictions, of about 0.9-4% in the PC and 1.3-6.8% in the HSS, being the highest improvements obtained in the SPI6 application.


      PubDate: 2015-11-14T17:09:46Z
       
  • Ground and surface water quality along a dambo transect in Chihota
           smallholder farming area, Marondera district, Zimbabwe
    • Abstract: Publication date: Available online 12 November 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): M. Wuta, G. Nyamadzawo, J. Mlambo, P. Nyamugafata
      In many smallholder farms in sub-Saharan Africa dambos are used for grazing and crop production especially horticultural crops. Increased use of dambos especially for crop production can result in ground and surface water pollution. Ground and surface water quality along a dambo transect in Chihota, Zimbabwe, was investigated between October 2013 and February 2014. The transect was divided into; upland (control), dambo gardens (mid-slope) and the river (valley bottom). Water samples for quality assessment were collected in October 2013 (peak of dry season) and February 2014 (peak of rainy season). The collected water samples were analysed for pH, faecal coliforms, total nitrogen, electrical conductivity, total dissolved solids (TDS), and some selected nutrients (P, K, Ca, Mg, Na, Zn, and Cu). Water pH was 7.0, 6.4 and 6.1 for river water, garden and upland wells respectively. During the wet season total nitrogen (TN) concentrations were 233 mg/L for uplands, 242 mg/L for gardens and 141 mg/L for the river. During the dry season, TN concentrations were all below 20 mg/L, and were not significantly different among sampling stations along the dambo transect. Dry season faecal coliform units (fcu) were significantly different and were 37.2, 30.0 and 5.0 for upland wells, garden wells and river respectively. Wet season faecal coliforms were also significantly different and were 428.5, 258.0 and 479.4 fcu for upland wells, garden wells and river respectively. The other measured physico-chemical parameters also varied with sampling position along the transect. It was concluded that TN and fcu in sampled water varied with season and that wet season concentrations were significantly higher than dry season concentrations. High concentrations of faecal coliforms and total N during the wet season was attributed to increased water movement. Water from upland wells, garden wells and river was not suitable for human consumption according to WHO standards during both dry and wet season.


      PubDate: 2015-11-14T17:09:46Z
       
  • Electrokinetic treatment of polluted soil at pilot level coupled to an
           advanced oxidation process of its wastewater
    • Abstract: Publication date: Available online 6 November 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): B. Ochoa, L. Ramos, A. Garibay, M. Pérez - Corona, M.C. Cuevas, J. Cárdenas, M. Teutli, E. Bustos
      Soil contaminated with hydrocarbons is a current problem of great importance. These contaminants may be toxic, can retain water and block gas exchange with the atmosphere, which produces a poor-quality soil unsuitable for ecological health. Electroremediation is among the treatments for the removal of such contaminants. In this research, a pilot-level electroremediation test was applied using a circular arrangement of electrodes with a Ti cathode at the middle of the cell surrounded by six IrO2 - Ta2O5 Ti anodes. The presence of an NaOH electrolyte helps to develop the electromigration and electro-osmosis of gasoline molecules (at 1 126 mg Kg-1) surrounded by Na+ ions. The hydrocarbons are directed towards the cathode and subsequently removed in an aqueous Na+ - hydrocarbon solution, and the -OH migrates to the anode. During electrokinetic treatment, the physicochemical characteristics of the soil close to either the cathode or anode and at the half-cell were evaluated during the three weeks of treatment. During that time, more than 80% of hydrocarbons were removed. Hydrocarbons removed by the electrokinetic treatment of gasoline-polluted soil were collected in a central wastewater compartment and subsequently treated with a Fenton-type advanced oxidation process. This achieved more than 70% mineralization of the hydrocarbons to CO2 and H2O within 1.5h; its low toxicity status was verified using the Deltatox® kit test. With this approach, the residual water complied with the permissible limits of COD, pH, and electrical conductivity for being discharged into water bodies, according to Mexican norm NOM-001-SEMARNAT-1996.
      Graphical abstract image

      PubDate: 2015-11-09T16:57:08Z
       
  • The Cone Penetration Test and 2D Imaging Resistivity as Tools to Simulate
           the Distribution of Hydrocarbons in Soil
    • Abstract: Publication date: Available online 31 October 2015
      Source:Physics and Chemistry of the Earth, Parts A/B/C
      Author(s): M. Pérez-Corona, J.A. García, G. Taller, D. Polgár, E. Bustos, Z. Plank
      The purpose of geophysical electrical surveys is to determine the subsurface resistivity distribution by making measurements on the ground surface. From these measurements, the true resistivity of the subsurface can be estimated. The ground resistivity is related to various geological parameters, such as the mineral and fluid content, porosity and degree of water saturation in the rock. Electrical resistivity surveys have been used for many decades in hydrogeological, mining and geotechnical investigations. More recently, they have been used for environmental surveys. To obtain a more accurate subsurface model than is possible with a simple 1-D model, a more complex model must be used. In a 2-D model, the resistivity values are allowed to vary in one horizontal direction (usually referred to as the x direction) but are assumed to be constant in the other horizontal (the y) direction. A more realistic model would be a fully 3-D model where the resistivity values are allowed to change in all three directions. In this research, a simulation of the cone penetration test and 2D imaging resistivity are used as tools to simulate the distribution of hydrocarbons in soil.
      Graphical abstract image

      PubDate: 2015-11-02T13:39:32Z
       
 
 
JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
 
About JournalTOCs
API
Help
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2015