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• Groundwater head increased up to 26.70 cm for the year 2060. • Land subsidence under the over-pumping scenario is specified. • The shoreline moves inland with a drawdown to 2, 9.50, and 14.80 m. • Future infrastructure planning should consider the land subsidence threat. Land subsidence (LS) due to the Sea Level Rise (SLR) and over-pumping was observed in many groundwater aquifers worldwide. The geotechnical properties and numerical simulation are considered a new integrative approach to investigate the LS hazard. This study investigates the environmental hazards related to LS in the quaternary sediments using laboratory and numerical modeling in the coastal aquifer of Nile delta, Egypt, due to SLR and over-pumping. Therefore, the geotechnical tests are conducted for the aquifer cap and classify the surficial soil as silty clay with moderately complex dispersive characteristics. In addition, hydraulic conductivity and one-dimensional consolidation of silty clay samples were analyzed to estimate the long-term settlement. Consequently, the groundwater head and drawdown were simulated for the current situation. Three proposed future scenarios are SLR and increased abstraction using the SEAWAT code. The results show that groundwater heads increased to 5.65, 14.50, and 26.70 cm for 2020, 2040, and 2060, respectively. Moreover, the estimated LS under the over-pumping scenario reached 7.60, 32.40, and 52.70 cm, with a maximum drawdown of 2.10, 9.70, and 15.10 m. SLR and over-pumping induce more inundation in the northern part due to SLR. The shoreline moves inland with a drawdown to 2, 9.50, and 14.80 m. Integration of measured and groundwater simulation settlements would provide appropriate information about the potential environmental hazards. Moreover, the future LS scenarios help stakeholders to make the right decision in developing effective measures in coastal aquifers to minimize the adverse impacts of LS on infrastructure waterways and human life. [ABSTRACT FROM AUTHOR]

Abstract: Laboratory batch experiments were designed to study the adsorption of cadusafos on two types of soils: clay loamy and sandy, collected from two regions around the Nile Delta in Egypt. The adsorption process is fast reaching equilibrium in 60min, decreases with increasing soil mass and independent on pH in the range 3–11. The experimental results were well fitted to linear partition model, and to a lesser extent to Freundlich non-linear model, Temkin and Dubinin–Radushkevich models. However, the 1/n parameter of Freundlich relation being of value around one supported the linear partition model. The K d values obtained from the linear model were 4.20 and 2.74L/g for sandy and clay soils, respectively. The energy of adsorption calculated from D–R equation was 4.36 and 5.04kJ/mol for clay and sandy soils, respectively, in the range assigned to physical forces. This kind of weak interaction, together with pH-independence implies that for the studied soils the organic content (that is higher in the clay soil) is not a major parameter in the adsorption of cadusafos. Water movement taking place more readily in sandy soil caused increased uptake relative to the case of clay soil. The higher uptake in sandy soil denotes that cadusafos may be mobile with a potential to leach and eventually pollutes ground water and surface water. The kinetics of adsorption was well fitted by the pseudo-second order equation. The intraparticles diffusion is of lower significance in case of sandy soil than in clay soil. Thermodynamic parameters indicated that the adsorption is spontaneous, endothermic accompanied by increase in entropy. [Copyright &y& Elsevier]

The conventional sub-surface drainage (FD) in the Nile delta clay soil, northern Egypt, results in excessive drainage and low irrigation efficiency (IE). However, a shallower placement of drain might reduce drain outflow and increase IE. The ultimate objective of the present study was to determine the optimum drain depth that minimizes drain outflow and maximizes IE and irrigation water use efficiency (IWUE), while maintaining crop yield and soil salinity. Compared to FD at 120 cm below the soil surface (BSS), the effect of four controlled drain depths (CD) at 40, 60, 80 and 100 cm BSS on drain outflow, IE, salinity buildup, yield and IWUE were investigated for two seasons (2017–18 and 2018–19; wheat-sunflower cropping system). Measurements were conducted for sunflower (as a summer crop). Irrigation was applied based on the soil water content of FD-treatment, thus irrigation depth varied for each treatment. The results showed that decreasing drain depth significantly reduced drain outflow and water input, while IE, seed yield and IWUE were increased. The maximum seed yield and IWUE were obtained at the shallowest drains. Compared with FD at 120 cm, drain depth at 40 cm decreased drain outflow (by 77.20%) and water input (by 29.3%), while increased seed yield and IWUE by 27% and 86%, respectively. Based on water balance, water-uptake from shallow groundwater was maximum for CD-40 cm treatment (31.05% of water-uptake) and was significantly higher than the other treatments. However, by the end of the second season, treatment with drain depth at 40 cm BSS recorded the highest soil salinity (3.6 dS m−1) due to the upward capillary rise of shallow groundwater. Increased soil salinity had no effect on seed yield because it was below the salinity threshold of sunflower. In terms of IE and IWUE, decreasing drain depth to 40 cm BSS is recommended, but with potential salinity buildup. Therefore, drain at 60 cm BSS (had similar seed yield to drain at 40 cm BSS) might lead to significant water-saving (21.8%), while maintaining seed yield and soil quality. In conclusion, modifying the drainage system by reducing drain depth and considering crop water-uptake from shallow groundwater might contribute to water saving. After all, careful water and soil management (e.g., periodic leaching), and suitable cropping systems should be considered for salinity management when decreasing drain depth. • Decreasing drain depth reduced drain outflow and water input and increased irrigation efficiency. • Shallow placement of drain increased seed yield and water use efficiency (WUE) of sunflower. • Shallow placement of drains makes the shallow groundwater available for crop use. • The maximum productivity and WUE were obtained at the shallowest drain depth (40 cm). [ABSTRACT FROM AUTHOR]

The new site is located in desert region of rugged topography. Quaternary boulders, gravels, sands and clays intercalation are the main rock types in the area. Geophysical evaluation of the subsurface lithology and structures using 2D and 3D electrical resistivity tomography (ERT) of the proposed site for construction was the main target of the present study, in addition finding empirical relationships between rock's electrical resistivity and some geotechnical parameters are also another target. Four geoelectrical resistivity layers were discriminated after the 2D inversion. Inspection of all 2D inverted profiles and 3D electrical resistivity depth slices showed rapid lateral and vertical variations in electrical resistivity values indicating heterogeneity in soil section. Clayey gravels or clayey sands and clays facies are predominant and hence swelling actions of the foundation beds is highly expected. The results of electrical resistivity tomography (ERT) were correlated with that inferred from the boreholes within the investigated area. The geotechnical parameters: liquid limit L.L%, plastic limit P.L%, free swelling F·S% and density Qu were calculated for representative samples collected from drilled boreholes. All samples showed considerably high L.L%, low to moderate P.L% with high F·S% which characterizes clayey soil. A trial for finding empirical relationships between the geotechnical properties and the rock electrical resistivity (L.L%, P.L%, F·S% and Qu) were carried out. These relations revealed that there is a considerable correlation between them when the rock has a resistivity more than 400 Ω m and poor correlation when the electrical resistivity is less than 400 Ω m. Accordingly, inferring applicable empirical equations between rock electrical resistivity and geotechnical parameters can be strong in the dry successions with a limited clays content, but in the wet or clayey soil materials the correlation will be weak and risky in application. From all obtained results and relationships, highly engineering awareness should be taken into account during establishing any construction in this site. • Establishing a new building needs high awareness by subsurface geologic features. • The results show rapid resistivity variation indicating heterogeneity in soil/rock. • Empirical equations between resistivity and geotechnical parameters were calculated. • The equations show a good correlation when the soil/rock has resistivities >400 Ωm. • The correlation is strong in dry sequences with limited clay and moisture contents. [ABSTRACT FROM AUTHOR]