The Tunisian Jurassic aquifer in the North African Sahara aquifer system: information derived from two-dimensional seismic reflection and well logs

Southern Tunisia is an arid area where socio-economic activities are dependent on groundwater resources. The presented study aims to better characterize the Jurassic aquifer based on geological and geophysical data, with a view to develop a rational exploitation program. Well logs are used to precisely determine the position and composition of the known Jurassic aquifer layers and to identify others able to produce good quality water. The logs show that limestones, sandstones and dolomites of the Krachoua, Techout and Foum Tataouine formations are the main Jurassic aquifers. Sixty-eight seismic-reflection sections are integrated within this study. The interpolation between the interpreted sections leads to the construction of isochronous isopach maps and geoseismic sections, and their analysis finds that compressive and extensive tectonic deformations have influenced the Jurassic aquifer geometry. The Hercynian orogeny phase manifestation is remarkable in that there are several stratigraphic gaps in the Jurassic sequence. The E–W, NW–SE, and NNW–SSE accidents, reactivated in normal faults since the Permian to Lower Cretaceous epochs, have generated the structures found in the Jurassic series, such as subsided and raised blocks. Their syn-sedimentary activity has controlled the thickness and facies of these series. The Cretaceous, Tortonian and Post-Villafranchian compressions are responsible for the Jurassic-deposits folding in some localities. The highlighted tectonic and sedimentary events have an important impact on the Jurassic aquifer function by favoring the Jurassic aquifer interconnections and their connections with the Triassic and Cretaceous permeable series.     

A comparative analysis among computational intelligence techniques for dissolved oxygen prediction in Delaware River

Most of the water quality models previously developed and used in dissolved oxygen (DO) prediction are complex. Moreover, reliable data available to develop/calibrate new DO models is scarce. Therefore, there is a need to study and develop models that can handle easily measurable parameters of a particular site, even with short length. In recent decades, computational intelligence techniques, as effective approaches for predicting complicated and significant indicator of the state of aquatic ecosystems such as DO, have created a great change in predictions. In this study, three different AI methods comprising: (1) two types of artificial neural networks (ANN) namely multi linear perceptron (MLP) and radial based function (RBF); (2) an advancement of genetic programming namely linear genetic programming (LGP); and (3) a support vector machine (SVM) technique were used for DO prediction in Delaware River located at Trenton, USA. For evaluating the performance of the proposed models, root mean square error (RMSE), Nash–Sutcliffe efficiency coefficient (NS), mean absolute relative error (MARE) and, correlation coefficient statistics (R) were used to choose the best predictive model. The comparison of estimation accuracies of various intelligence models illustrated that the SVM was able to develop the most accurate model in DO estimation in comparison to other models. Also, it was found that the LGP model performs better than the both ANNs models. For example, the determination coefficient was 0.99 for the best SVM model, while it was 0.96, 0.91 and 0.81 for the best LGP, MLP and RBF models, respectively. In general, the results indicated that an SVM model could be employed satisfactorily in DO estimation.     

Potential ecological risk assessment,enrichment, geoaccumulation,and source identification of metals in the surface sediments of Choghakhor Wetland,Iran

This study reported the first comprehensive research on identification of metal concentrations (Fe, Mg, Mn, Pb, Cd, Cr) in order to provide baseline data for future studies, identify possible sources, determine degree of pollution, and identify potential ecological risks of metals in surface sediments from Iran’s Choghakhor Wetland. The order of metal concentration was as follows: Fe > Mg > Mn > Pb > Cd > Cr, with mean concentrations of 6140.35, 1647.32, 289.03, 1.10, and 0.45 µg/g of dry weight, respectively. These results reveal that Choghakhor Wetland is not heavily polluted compared to other regions. The results of enrichment factor (EF) and geoaccumulation index (I _geo) showed that Fe, Pb, Mg, Cr, and Mn presented low levels of contamination and probably originated from natural sources. On the other hand, the results of EF and I _geo indices suggested that Cd concentrations in sediments of Choghakhor Wetland originated from anthropogenic sources. Based on the results of three sets of sediment quality guidelines, only Cd concentration in sediments of Choghakhor Wetland is a threat for aquatic organisms of Choghakhor Wetland. The results of multivariate analysis such as principal component analysis and cluster analysis showed that Fe–Mn, Cr–Mg, and Pb groups originated from natural sources, while Cd concentrations in sediments of Choghakhor Wetland originated from both natural and anthropogenic sources (mainly chemical fertilizers). To our knowledge, this is the first study about metal concentrations in sediments of Choghakhor Wetland, and because of low levels of these metals, these concentrations can be considered background levels for future investigation.     

Comparison between inductively coupled plasma and X-ray fluorescence performance for Pb analysis in environmental soil samples

Comparison of two conventional analytical techniques such as X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS) for measuring Pb concentrations in soil samples was achieved using field and laboratory work. Seventy-three samples were collected from urban areas surrounding the large lead smelter at South Australia, as an indicator of the environment impact of smelter activity. Soil Pb concentrations were determined using hand-held XRF analyser under laboratory conditions. ICP-MS analysis on digested soils (using a microwave-assisted nitric acid digestion-extraction) was applied to validate p-XRF data. The analysis showed that Pb concentrations determined by XRF correlated with high linearity with Pb concentrations determined by ICP-MS measurements (R ² = 0.89). Statistical test (t test) was applied to the data of both methods applied without any significant difference between the two techniques. These results indicated that ICP-MS corroborated XRF for Pb soil measurements and suggests that XRF was a reliable and quick alternative to traditional analytical methods in studies of environmental health risk assessment, allowing for much larger sampling regimes in relatively shorter times and could be applied in the field.     

Groundwater potential recharge estimation in bare soil using three soil moisture accounting models: field evaluation for a semi-arid foothill region

Performances of conventional and improved soil moisture balance as well as locally calibrated empirical models were evaluated in simulating potential recharge (R) and soil moisture content for a semi-arid foothill region. Models comparison with observed values using lysimeter data during [(2011–2012), (2012–2013)] reveal poor performance of conventional soil moisture balance model, underestimating annual R values. Improved soil moisture balance model provided acceptable estimation of annual R for 2011–2012 by considering the wetting of the near surface soil storage. However, it produced the worst simulation for daily soil moisture content once rainy season was over. Sensitivity analysis revealed that the precision degree of initial soil moisture deficit value would strongly influence estimation of R by improved soil moisture balance model, which can be viewed as a limiting factor. Additionally, locally calibrated model produced the best estimation of annual R and daily soil moisture content, which is suggested for the study region.     

Quaternary fossil coral communities in uplifted strata along the Balochistan coast of Pakistan: understanding modern coral decline in the Arabian Sea

Uplifted reefs due to being important palaeoclimate archives and a rich source of information on past physical and geochemical changes globally have become the centre of marine research. The uplifted fossil Quaternary coral communities of Jiwani and Gwadar are perfect places to study the palaeoclimatic and geological changes that have shaped the Balochistan coast. Studies on the palaeodiversity of corals along the Makran coast of Pakistan are lacking. In the present study, the samples collected using line intercept method from four uplifted sites (Balochistan coast: one at Gwadar and three at Jiwani) were analysed. The relative distribution and diversity of scleractinian fossil corals was determined, and the factors responsible for coral decline along Pakistan coast were compared with modern coral distribution and diversity. A total of 48 fossil coral species were recorded in nine families and 22 genera. High coral diversity was recorded in the uplifted landward sites of Jiwani and Gwadar headland. Terraces close to the shore at Jiwani had lower diversity. The corals seem to be Quaternary: most likely Pleistocene to Holocene. The modern fauna lacks many species recorded in the fossil community, thus suggesting a faunal turnover in diversity and redistribution of coral fauna which may be linked with past geological events and increasing anthropogenic pressure.     

Mapping of soil organic carbon stock in the Arab countries to mitigate land degradation

Soil organic matter is a key soil component that plays a critical role in ecosystem functioning including soil productivity and resilience to erosion and drought. Most Arab countries are located in semi-arid and arid areas with dominance of drylands soils with poor organic matter content and soil quality. In line with the efforts of the FAO Global Soil Partnership (GSP) and French initiative for carbon sequestration (4 par mille); the soil organic carbon (OC) stock in the Arab countries was assessed and mapped using the FAO-UNESCO Digital Soil Map of the World (DSMW). The outputs must serve awareness raising both at the level of land users and decision makers. Results were compared with the only available national OC map, recently produced in Lebanon. Other national OC maps are under processing by the GSP and Intergovernmental Technical Panel on Soils (ITPS) within the Global Soil OC Map. Produced maps showed low OC stock in the topsoil of more than 69% of the cultivated soils with dominance of xerosols, arenosols, and lithosols. The average soil OC stock in the Arab countries is 37 ± 36 ton/ha in the topsoil and 78 ± 69 ton/ha in the standard soil depth. The total OC stock in the arable lands of the Arab countries was estimated at 50.5 gigatons (GT) with Sudan, Saudi Arabia and Algeria placed on top. The average total OC stock per one Arab country is 0.8 ± 1.7 million tons. Large standard deviation points to different pedoclimatic conditions but also to variable management and land use history. Water erosion and chaotic urban expansion caused the irreversible loss of 25 and 53.6 GT tons of OC, respectively. With increased pressure on limited soil resources, policies must address soil conservation and C sequestration to support soil productivity and improve food production.     

Environmental assessment of soil,groundwater, and surface water quality in the south of the Riyadh,Saudi Arabia

To understand the impact of the influence of treated wastewater, a study was undertaken in the downstream side of Wadi Hanifa in the southern part of Riyadh City in Saudi Arabia. Chemical elements from 17 groundwater samples, 9 surface water samples (treated wastewater), and 14 soil samples were analyzed. Water facies analyses showed that both groundwater and surface water belong to the SO₄-Cl class. However, the groundwater is characterized by high salinity (average value of 3547 mg/l), which may be result of the greater rock-water interaction and limited rainfall recharge. The NO₃ values are also high in the groundwater samples (average value of 40 mg/l) and are mainly attributed to the agricultural practices in the study area. The surface water samples (treated wastewater from the plant) shows an average salinity value of 1232 mg/l and is better suited for irrigation purposes. Heavy elements analyzed in the soil samples show high concentrations of all the elements except Mn and Ni as compared to their background concentration. Enrichment factor and index of geoaccumulation calculated from the soil samples indicate that they are severely enriched with respect to Cd and Se. The spatial distribution maps were prepared based on kriging interpolation technique to estimate the concentrations of the analyzed elements at unknown locations. The treated wastewater in the study area is better suited for agricultural and domestic activities as compared to groundwater.     

Seismotectonics and consequences of the 1930s large earthquakes in eastern Mazandaran,north of Iran

Early in the 1930s,two relatively large earthquakes (Kosout,magnitude 6.8,and Talarrud,magnitude 5.8) shook the eastern Mazandaran,northern Iran.Despite the his...