An overview of phosphate rocks and their mining impact on groundwater,Eastern Desert,Egypt

The Eastern Desert of Egypt represents a remote arid area which is scarce in water resources. The area is characterized by many mining sites to exploit the phosphate deposits; thus, these activities can generate groundwater contaminants. The main objective of the present study is discussing the effect of the mining activities and phosphate bearing rocks on groundwater. The obtained results pointed out that the water bearing formations can be distinguished as Quaternary alluvial, Oligocene sandstone, Campanian phosphate limestone (Duwi Formation), and Precambrian basement rocks. Some of the investigated groundwater shows relatively high concentrations of trace elements compared to other samples, such as Pb, Zn, Cu, Cr, Ni, and Sr. This is consistent with the analyses of phosphate rocks which are also enriched in the same trace elements. The high groundwater salinity is due to evaporation, limited re-charge, and leaching of salts in rocks. The results of speciation modeling reveal that majority of groundwater samples are supersaturated with calcite, aragonite, and dolomite, and some samples are also at equilibrium or supersaturated with hydroxyapatite. The groundwater quality in the study area evaluated for human drinking, livestock and poultry domestic, and industrial purposes is not suitable in most wells. It is obvious that the groundwater contamination occurs when drilling wells penetrate the phosphate bearing beds and not only at mining activity sites. Therefore, it is recommended to avoid any groundwater exploration from the Duwi Formation and also select the drilling sites outside the mining areas.     

A novel triggerless approach for mass wasting susceptibility modeling applied to the Boston Mountains of Arkansas,USA

This research deploys a novel mass wasting susceptibility modeling approach for cases where temporal information is unavailable and circumstances are prejudiced to merit applying traditional susceptibility modeling strategies. Conventional models typically employ approaches deemed problematic for this study, e.g., biased weighted input; a “more is better” approach pertaining to voluminous inputs; neglecting geologic structural influence; and establishing temporal linkages between cause (trigger) and effect (failure) with a trigger being defined as a catalyst for failure, such as timed events like earthquakes or precipitation as well as physical changes like vegetation removal or slope disturbance. Road bias may also influence modeling dramatically when event data are derived from observations of road-related failures, which become unreliable at predicting susceptibility in regions with no roads. However, a triggerless approach can extrapolate naturally occurring susceptibility via priori knowledge of local topography and structural geology factors. Two models are then created for comparison: One model has integrated empirical Bayesian kriging and fuzzy logic considering basically local topography and structural geology, while the second model has employed a standard implementation of a weighted overlay using all available (8) input data layers. Statistical comparisons show that the first model has identified ~ 83%, compared to only ~ 28% for the latter model, of the 47 documented mass wasting events in the selected study site. These results demonstrate that the introduced triggerless approach is efficiently capable of modeling mass wasting susceptibility in areas lacking temporal datasets, which in turn can help in mitigating future geohazards.     

GIS-based landslide susceptibility evaluation using fuzzy-AHP multi-criteria decision-making techniques in the Abha Watershed,Saudi Arabia

Landslides are natural geological disasters causing massive destructions and loss of lives, as well as severe damage to natural resources, so it is essential to delineate the area that probably will be affected by landslides. Landslide susceptibility mapping (LSM) is making increasing implications for GIS-based spatial analysis in combination with multi-criteria evaluation (MCE) methods. It is considered to be an effective tool to understand natural disasters related to mass movements and carry out an appropriate risk assessment. This study is based on an integrated approach of GIS and statistical modelling including fuzzy analytical hierarchy process (FAHP), weighted linear combination and MCE models. In the modelling process, eleven causative factors include slope aspect, slope, rainfall, geology, geomorphology, distance from lineament, distance from drainage networks, distance from the road, land use/land cover, soil erodibility and vegetation proportion were identified for landslide susceptibility mapping. These factors were identified based on the (1) literature review, (2) the expert knowledge, (3) field observation, (4) geophysical investigation, and (5) multivariate techniques. Initially, analytical hierarchy process linked with the fuzzy set theory is used in pairwise comparisons of LSM criteria for ranking purposes. Thereafter, fuzzy membership functions were carried out to determine the criteria weights used in the development of a landslide susceptibility map. These selected thematic maps were integrated using a weighted linear combination method to create the final landslide susceptibility map. Finally, a validation of the results was carried out using a sensitivity analysis based on receiver operator curves and an overlay method using the landslide inventory map. The study results show that the weighted overlay analysis method using the FAHP and eigenvector method is a reliable technique to map landslide susceptibility areas. The landslide susceptibility areas were classified into five categories, viz. very low susceptibility, low susceptibility, moderate susceptibility, high susceptibility, and very high susceptibility. The very high and high susceptibility zones account for 15.11% area coverage. The results are useful to get an impression of the sustainability of the watershed in terms of landsliding and therefore may help decision makers in future planning and mitigation of landslide impacts.     

Metasomatism and origin of glass in the lithospheric mantle xenoliths beneath Ain Temouchent area (North-West Algeria)

A spinel ± amphibole ± feldspar bearing Iherzolites, a spinel ± amphibole ± feldspar bearing harzburgites, and a spinel ± amphibole ± phlogopite bearing wehrlites are metasomatized peridotitic mantle xenoliths from Ain Temouchent volcanic complex (North-West Algeria). These xenoliths are metamorphic/deformed rocks with a strong planar fabric typical of mantle tectonites. The wehrlites are not the result of a simple model of partial melting. The spinel ± amphibole ± feldspar bearing harzburgites and lherzolites exhibit asymmetric concave-shaped REE patterns. These indicate that an earlier partial melting event was followed by metasomatic processes. The wehrlites have higher REE concentrations and LREE/HREE fractionations, indicating a sequential evolution of wehrlites from previous refractory material with melting as an addition process. This process reflects the interaction of the lithospheric mantle beneath the Ain Temouchent area with basaltic melt. Metasomatism is expressed by the formation of amphibole, phlogopite, and increased abundances of clinopyroxene at the expense of orthopyroxene, in lherzolite and harzburgite. In the Ain Temouchent area, metasomatizing agents are Na-alkali silicates. The similarities observed between the glasses studied in this paper, and the basaltic host rocks of the Ain Temouchent area, may suggest a common mantle source, or with chemical similarities but with relatively different evolutions pathways. The formation of glass in wehrlites from the Ain Temouchent area has an origin formed by the breakdown of amphibole or phlogopite as a result of decompressional melting and production of silica-undersaturated glasses. The glass reacts with essentially orthopyroxene to produce silica-rich glasses. This study has contributed to highlighting a relationship between glass, and the processes that caused the formation of metasomatic phases.     

Land degradation risk assessment in Al-Sawda terraces,Kingdom of Saudi Arabia

Monitoring of soil properties is a significant process and plays an important role about how it can be used sustainably. This study was performed in a local area in Sawda Mountains KSA to map out some soil properties and assess their variability within the area under different land cover. Soil sampling was carried out in four different sites using the grid sampling technique. Ten samples were collected in each location within a 10 by 10 km area; soil was sampled at 0–30-cm depth. The soil samples were air-dried, crushed, and passed through a 2-mm sieve before analyzing it for pH, EC, CaCO₃, organic matter contents, and bulk density. The thematic maps of these characteristics were produced using ArcGIS 10.0 software. Finally, the land degradation was assessed using three factors: soil salinization, compaction, and edibility. The obtained results showed that the high risk of soil compaction, salinization, and erodibility occupied an area 5.6 ha (17.5%), 3.7 ha (11.54%), and 8.1 ha (25.3%), respectively, in the surface soil layer. The land degradation risk in the study area due to salinization was low to high; however, the degree of soil compaction was moderate to very high. The K-factor (soil erodibility) in the area ranged between 0.1 and 0.35 Mg h MJ^?1 mm^?1, and most of the study area was located in moderate to high erodibility classes.     

Cretaceous paleomargin tilted blocks geometry in northern Tunisia: stratigraphic consideration and fault kinematic analysis

New stratigraphic data, lithostratigraphic correlations, and fault kinematic analysis are used to discuss the basin geometry and sedimentation patterns of the northeastern Tunisia during Cretaceous times. Significant facies and thickness variations are deduced along the northeastern Atlas of Tunisia. The NW-SE 80-km-long regional correlation suggests a high sedimentation rate associated with irregular sea floor. The fault kinematic analysis highlights N-S to NE-SW tectonic extension during Early Cretaceous. During Aptian–Albian times, an extensional regime is recognized with NE-SW tectonic extension. The Cenomanian–Turonian fault populations highlight a WNW-ESE to NW-SE extension, and Campanian–Maastrichtian faults illustrate an NW-SE extension. The normal faulting is associated to repetitive local depocenters with a high rate of sedimentation as well as abundant syntectonic conglomeratic horizons, slump folds, and halokinetic structures. The sequence correlation shows repetitive local depocenters characterizing the basin during Early Cretaceous times. All the above arguments are in favor of basin configuration with tilted blocks geometry. This geometry is shaped by major synsedimentary intra-basin listric normal faults, themselves related to the extensional setting of the southern Tethyan paleomargin, which persisted into the Campanian–Maastrichtian times. The results support a predominant relationship between tilted blocks geometry and sedimentation rather than E-W “Tunisian trough” as it was previously accepted.     

Gaseous air pollution background estimation in urban,suburban, and rural environments

There is a great demand for estimating the ambient air pollutant background concentrations in order to assess the effectiveness of different emission control strategies. In this paper, the background concentrations of four pollutants, namely sulfur dioxide (SO₂), nitrogen oxides (NOx), carbon monoxide (CO), and ozone (O₃) pollutants in urban, suburban, and rural environments were investigated using Kolmogorov–Zurbenko (KZ) filter technique. Air quality data from monitoring stations over a period of 4 years (2007–2010) was analyzed for three locations in Kuwait, namely urban, suburban, and rural. The spatial and temporal (daily, weekly, and monthly) variations of the four pollutants were analyzed. The results show that the levels of ambient air pollutant background concentrations were high in the urban site compared to suburban and rural area. The diurnal variation of SO₂ concentration showed an early morning peak, while the diurnal variation of NOx concentration constituted has two peaks, one was in the early morning hours (5 to 8 a.m.) and the second was in nighttime hours (8 to 11 p.m.). These two peaks were observed at all three locations. The monthly background NOx concentration reached a maximum in winter and minimum in summer. Diurnal variation of CO concentration showed a similar trend to SO₂ concentrations in all three locations. Because of the photochemical reactions that occur in the atmosphere, the background concentration of O₃ showed an inverse relation with respect to background concentration of NOx.     

Hydrogeological characterization of a carbonate aquifer using geophysical and geochemical approach: case of the Krachoua Formation in Tataouine area,Southern Tunisia

An integrated hydrogeological investigation involving geological surface data, well data (lithostratigraphical and piezometric data) and the vertical electrical sounding (VES) method was carried out in Tataouine area, Southern Tunisia to characterize the hydrogeology and the geochemistry of the Krachoua Formation aquifer. The electrical data were used to differentiate lithostratigraphic units and characterize their hydrogeological potentialities. Major elements contents within groundwater samples were assessed and some plots and diagrams have been established in order to investigate the hydrochemical properties of this aquifer and the origin of its mineralization. The Krachoua aquifer exhibits a general drawdown of the piezometric level from 2004 to 2015 reflecting a dramatic decrease in groundwater resources due to increased groundwater abstraction during the last decades. Flow directions shows that the recharge of this aquifer considered as a free aquifer is directly ensured by rainfalls over the outcropping fractured limestones. The geometry of the Krachoua Formation aquifer is tectonically controlled and structured in horst and graben features that impacted greatly the hydrogeology and the hydrodynamics of the area. Subsequent thickness and facies variations within this aquifer influenced the reservoir quality and the groundwater flows. The increased values of salinity to the northwest of the study area seems to be mainly related to the dissolution of the Upper Liassic gypsum of Mestaoua Formation which outcrops widely and can be dissolute easily by meteoric water and contaminate the Krachoua aquifer. This fact is also supported by the sulfated and calci-magnesian chloride facies of this aquifer related to the dissolution of evaporitic rocks (gypsum, anhydrite, and halite). However low salinity values are recorded within the zone where these evaporitic rocks are relatively deep.     

Fungal biodiversity in sewage water under the effect of calcium hydroxide and hydrogen peroxide into two-steps treatment

Microorganisms, organic matter, heavy metals are the main pollutants in sewage water. The increasing water demand pressurized people to use the sewage water. Different systems, chemicals and physical treatments were used in sewage water treatment. The aim of this work is to study the effect and correlations of primary (Ca(OH)₂ filtration and H₂O₂) and secondary (dissolved oxygen, organic matter, conductivity, pH and OD) factors on fungi present in sewage water in addition to proving the sequence of the system used in the current study. After treatment, fungi were examined, identified on Czapek agar and analyzed using multivariate tools (CANOCO: DCA and CCA) and R software. The treatment includes two main steps: liming filtration and oxidation, respectively. All parameters were negatively or positively correlated (organic matter, pH, conductivity %, optical density, fungal CFU ml^?1, dissolved oxygen). Heavy metals were decreased due to the application of Ca(OH)₂ and H₂O₂, respectively. There were two main groups of fungi. The larger was correlated with the organic matter, whereas the second was tolerating calcium hydroxide concentrations. Aspergillus sydowii tolerated hydrogen peroxide (0.2 mll^?1(33%); Ca(OH)₂, 0.25 gl^?1). Sequential steps treatment was healthy and economically efficient. The proposed system improved water characteristics. The recommended amount of Ca(OH)₂ and H₂O₂ was 0.25 gl^?1 and 0.2 mll^?1(33%), respectively, and can remove more than 99.9% of fungal CFUs. The current study minimized the optimum dose of hydrogen peroxide used in the disinfection of sewage water from 1.5 (Mohamed in Chem Eng J 119:161–165, 2006) to 0.2 mll^?1 of H₂O₂ (the current study).     

Assessment of Aquifer Storage and Recovery (ASR) feasibility at selected sites in the Emirate of Abu Dhabi,UAE

Aquifer storage and recovery (ASR) is considered as a strategy for the storage of water to ensure a sustainable water supply in the Abu Dhabi emirate. Earlier investigations have been conducted, and two sites were proposed for the installation of ASR in the surficial aquifer. Recently, the site located in the center of Abu Dhabi (sand dune area) was executed, and the second site is undergoing the pilot phase of the study. However, the performance and influence of the regional groundwater system may vary depending on regional hydrogeological characteristics, which have not been investigated. Hence, this study attempts to understand the feasibility of the proposed ASR sites in the surficial aquifer using a regional model developed by the finite-difference approach with an accuracy of 0.28 m mean residual difference. Additionally, six sites were selected on the basis of the literature and aquifer parameters and were investigated for their suitability for future ASR installation. Six cycles of injection and recovery at various rates were analyzed at each ASR site by using a transient calibrated model until the end of the year 2030. The area of influence is axisymmetrical in the sand dune area and non-symmetrical in the east and northeastern areas because of the steep topography and groundwater table gradient. At the sites that possess a non-symmetrical influence, the area of influence is always high upstream of the groundwater flow. Heterogeneity-induced variation in the fluctuation of the groundwater table is noted in all sites. Even with 100% recovery, the groundwater table did not reach the ambient groundwater table during the recovery period. This finding confirms the contribution of regional groundwater to the site during recovery. All sites selected for future ASR installation, except site 5, are capable of storing the volume needed to meet expected water demand. Site 2 is considered the most suitable site for ASR installation in the future. This study will facilitate the scientific communities and authorities in understanding the feasibility of ASR installation for sustainable water storage and supply in the Abu Dhabi emirate.