Better constrained selection of the Paleozoic West Gondwana (South America) paleomagnetic poles for the APWP determination

The reliability of an Apparent Polar Wander Path (APWP) obviously depends on the paleomagnetic poles used to determine it. The APWP of Africa and South America are fairly well defined for the 330–260 Ma interval. However, this study pointed out a moderate shift between these two curves, and an incoherency of the South American data, contrary to the African ones, which are homogeneous. A number of South American pole positions were re-evaluated in an effort to better constrain the APWP for the entire continent. Most of discarded poles correspond to sites at the area of the junction of Cordillera with the stable craton. That could have structural implications for the evolution of the western margin of the Gondwana. A new criterion for the evaluation of paleomagnetic poles reliability for APWP is presented. Based on comparison of data from different continents and labeled “coherence” criterion, it is independent from Van der Voo’s ones.     

GIS based DRASTIC model for groundwater vulnerability assessment: Case study of the shallow mio-plio-quaternary aquifer (Southeastern Tunisia)

Groundwater is the main source of water in arid regions. Thus, groundwater pollution becomes a major issue due to the increasing contamination, which poses serious and harmful risk to the environment. Groundwater vulnerability maps can be used as a tool to help decision makers to protect groundwater resources from contamination. The vulnerability of the Mio-Plio-Quaternary shallow aquifer (Southeast Tunisia) has been assessed using a DRASTIC model based on Geographic Information System (GIS). The different parameters of the model were collected from several sources and converted into thematic maps using ArcGis©. Each DRASTIC parameter was assigned a weight and rating based on a range of information within the parameter. Groundwater vulnerability map shows a large area (48%) with high risk of pollution. It indicates that the Southern part of the aquifer and the wadi beds are the most susceptible to contamination. The measured nitrate concentration is coherent with the DRASTIC model results.     

Upper crustal Poisson’s ratio and coda-wave attenuation beneath Eastern Anatolia

The attenuation of seismic waves reflects the elastic nature of the media within which the waves propagate. In this study, we calculate the Coda-Q(Q_c), frequency dependence(η), Vp/Vs and Poisson's(υ) ratios by using 2621 vertical component seismograms generated by 987 earthquakes recorded by 13 seismic stations in Eastern Anatolia, and creat a 2-D seismic tomographic Q_c model for the region. The obtained model provides significant information for exploring the boundaries of adjacent tectonic units within the upper crust and interpreting their dynamic characteristics. The 2-D Q_c model and the other parameters are consistent with the seismotectonic features of Eastern Anatolia. Highly heterogeneous Q_c values are observed in the study area dividing it into north-south directed bands of low and high attenuation. The highest η values were obtained beneath the northwestern and eastern parts of the study region. Clear, high and low υ values are obtained in the western and eastern parts of the study area, respectively. The spatial variations in the measured parameters are consistent with many geophysical observations including low Pn velocities, efficient Sn blockage, high heat flow, and widespread volcanism. Different upper crustal thicknesses and inhomogeneous stress distribution along the East and North Anatolian Fault Zones may also contribute to the observed heterogeneities.     

Supported TiO2 on Kaolin,Cordierite, and Calcite for Photocatalytic Removal of Dyes from Wastewater

Kaolin, cordierite, and calcite are investigated as supports for TiO₂. The prepared TiO₂/support samples are examined for the removal of organic dyes from wastewater. The samples are preliminarily investigated to identify the optimal loaded system using synthetic wastewater containing methylene blue (MB). Data indicate that the investigated support significantly affects the photocatalytic activity of the supported TiO₂. Low photocatalytic activity toward MB degradation is observed upon using TiO₂/calcite when compared to the unsupported TiO₂. Interaction between calcite and titania species probably occurrs to produce the less photoactive CaTiO₃ amorphous species. Anatase TiO₂ is obtained upon using kaolin and cordierite as supports. The low photocatalytic performance of the TiO₂/kaolin sample is also observed. A high concentration of MB on TiO₂/kaolin surfaces blocks the photoactive sites. TiO₂/cordierite shows the highest photocatalytic activity compared to the unsupported TiO₂ as well as the other TiO₂/support samples. Rigid cordierite particles suppress the agglomeration of TiO₂ particles during the preparation, leading to a high exposed surface of TiO₂ towards light illumination. TiO₂/cordierite is investigated for the removal of organic dye from real wastewater collected from a textile dyeing factory. Color removal of up to 46% is achieved upon UV irradiation.     

Stochastic Forecasting Models of the Monthly Streamflow for the Blue Nile at Eldiem Station

Egypt is almost totally dependent on the River Nile for satisfying about 95% of its water requirements. The River Nile has three main tributaries: White Nile, Blue Nile, and River Atbara. The Blue Nile contributes about 60% of total annual flow reached the River Nile at Aswan High Dam. The goal of this research is to develop a reliable stochastic model for the monthly streamflow of the Blue Nile at Eldiem station, where the Grand Ethiopian Renaissance Dam (GERD) is currently under construction with a storage capacity of about 74 billion m³. The developed model may help to carry out a reliable study on the filling scenarios of GERD reservoir and to minimize its expected negative side effects on Sudan and Egypt. The linear models: Deseasonalized AutoRegressive Moving Average (DARMA) model, Periodic AutoRegressive Moving Average (PARMA) model and Seasonal AutoRegressive Integrated Moving Average (SARIMA) model; and the nonlinear Artificial Neural Network (ANN) model are selected for modeling monthly streamflow at Eldiem station. The performance of various models during calibration and validation were evaluated using the statistical indices: Mean Absolute Error, Root Mean Square Error and coefficient of determination (R2) which indicate the strength of fitting between observed and forecasted values. The results show that the performance of the nonlinear model (ANN) was much better than all investigated linear models (DARMA, PARMA and SARIMA) in forecasting the monthly flow discharges at Eldiem station.     

Change in low flows due to catchment management dynamics—Application of a comparative modelling approach

Understanding the natural low flow of a catchment is critical for effective water management policy in semi-arid and arid lands. The Geba catchment in Ethiopia, forming the headwaters of Tekeze-Atbara basin was known for its severe land degradation before the recent large scale Soil and Water conservation (SWC) programs. Such interventions can modify the hydrological processes by changing the partitioning of the incoming rainfall on the land surface. However, the literature lacks studies to quantify the hydrological impacts of these interventions in the semi-arid catchments of the Nile basin. Statistical test and Indicators of Hydrological Alteration (IHA) were used to identify the trends of streamflow in two comparatives adjacent (one treated with intensive SWC intervention and control with fewer interventions) catchments. A distributed hydrological model was developed to understand the differences in hydrological processes of the two catchments. The statistical and IHA tools showed that the low flow in the treated catchment has significantly increased while considerably decreased in the control catchment. Comparative analysis confirmed that the low flow in the catchment with intensive SWC works was greater than that of the control by >30% while the direct runoff was lower by >120%. This implies a large proportion of the rainfall in the treated catchment is infiltrated and recharge aquifers which subsequently contribute to streamflow during the dry season. The proportion of soil storage was more than double compared to the control catchment. Moreover, hydrological response comparison from pre- and post-intervention showed that a drastic reduction in direct runoff (>84%) has improved the low flow by >55%. This strongly suggests that the ongoing intensive SWC works have significantly improved the low flows while it contributed to the reduction of total streamflow in the catchment.     

Rare Earth Elements Around the Barakah Nuclear Power Plant,UAE

Natural Resources Research - Rare earth element (REE) contamination has major consequences for the environment and humans. Some forms of REEs have more serious environmental impacts than others. It...     

Atmospheric Water Harvesting from Low-Humid Regions of Hail City in Saudi Arabia

Natural Resources Research - Atmospheric water harvesting (AWH) is emerging as a promising technique of water production in remote and isolated areas away from natural water resources. The present...     

Copepod community structure during upwelling and non-upwelling seasons in coastal waters off Cochin, southwest coast of India

Vypeen, an island of Cochin estuarine system, acts as the spawning site of several marine and estuarine fishes. We assumed that, physical process(upwelling) make changes in hydrography and the production of chlorophyll a in coastal waters off Vypeen. These alterations can influence the zooplankton abundance and copepod community structure in that area. For justifying this hypothesis, samples were collected from Vypeen at 10 m and 30 m locations during January(pre-southwest monsoon), August(late-southwest monsoon) and November(postsouthwest monsoon) 2014. During August, subsurface water column was cool, nutrient rich and less oxygenated(signatures of upwelling) than in November and January. Maximum concentrations of nitrate and chlorophyll a were recorded during August. In the present study, 15 zooplankton groups were recorded; of which copepods were the most predominant group(73%–90%). Copepod density in the present study ranged between 527.2 ind./m~3 and 5 139.2 ind./m~3. Totally, 37 copepods species were reported in present study and copepod species richness was higher during January. The abundance of zooplankton and copepods was high in August during late-southwest monsoon. These variations were closely associated with the coastal upwelling in August and weakening of moderate upwelling in November. In SIMPER analysis, it was found that the copepods species distribution was similar within season and dissimilar between the three seasons. Moreover, the higher abundance of upwelling indicator species Temora turbinata was recorded in August, which confirms the signs of seasonal upwelling in Vypeen. The present study emphasized on the influence of hydrographical parameters associated with physical process, in governing the copepod community organization of the Vypeen Island.