Talal Alharbi

Metal pollution in Al-Khobar seawater, Arabian Gulf, Saudi Arabia

In order to assess heavy metals pollution along the Al-Khobar coastline, 30 seawater samples and 15 sediment ones were collected for Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Hg and Pb analysis by Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). The analysis indicated a southward decreasing pattern in most heavy metal concentrations and the average values of Zn, Fe, Mn, Cu, As and Cr were higher than the ones reported from some worldwide seas and gulfs. Most of the highest levels were recorded within the bays and were related with in situ under sediments especially that composed of clays and very fine sands, and in localities characterized with anthropogenic activities like landfilling, desalination plants, fishing boats, oil spills and solid rubbish. The results of the present study provide useful background for further marine investigation and management in the Arabian Gulf region.

Integrating geochemical investigations and geospatial assessment to understand the evolutionary process of hydrochemistry and groundwater quality in arid areas

Groundwater is the key for life in arid areas. Aquifer overexploitation and climatic conditions can significantly deteriorate groundwater quality. The Al-Qassim area in central Saudi Arabia is characterized by dense agricultural use and is irrigated mainly by fossil groundwater from the Saq Aquifer. Understanding the area’s hydrochemistry, major factors governing groundwater quality, and alternative uses of the groundwater are the main goals of this study. Groundwater samples were collected and examined for major, minor, and trace elements. Ionic relationships, hydrochemical facies, geospatial distributions, and multivariate analyses were conducted to assess the hydrochemical processes at play. The salinity and nitrate concentrations of the Saq Aquifer’s groundwater were found to increase in the outcrop areas more than the confined areas. The spatial distributions were fragmented by three main factors: (i) modern recharge by relatively brackish water, (ii) irrigation return flow in intensive farming areas, and (iii) overexploitation and draining of deep and relatively saline zones of the aquifer. Seven water types were found representing the alkaline water with a predominance of sulfate–chloride ions and earth alkaline water with a predominance of sulfate and chloride. Mixing between fresh and brackish water, dissolution of mineral phases, silicate weathering, and reverse ion exchange were recognized as the evolutionary processes, while evaporation played a minor role. Cluster analyses characterized the fresh groundwater zone, modern groundwater recharge zone, and anthropogenic influence zone. In the confined areas, nearly all the groundwater was appropriate for domestic use and irrigation. In the outcrop areas, some limitations were found due to unsuitable conditions.

Geotechnical investigation of the El-Elb dam site, northwest Riyadh, Saudi Arabia, using 2D resistivity and ground-penetrating radar techniques

In the present study, the existence of cavities, voids, and fractures was verified at the site of the El-Elb Dam, which is located to the northwest of Riyadh City across Wadi Hanifa, using 2D electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) techniques. For this purpose, four ERT profiles were measured on the downstream side of the El-Elb Dam using the Syscal Pro Switch-72 resistivity meter. In addition, a GPR survey using a 400-MHz antenna and a SIR-3000 instrument was conducted along five profiles above the stilling basins on the downstream side of the dam and one radar profile was measured outside the stilling basins area across the course of the wadi. The resultant geophysical data were interpreted with the aid of information from a field-based structural and stratigraphic evaluation of the outcropped bedrock on the banks of the wadi course. The analysis of the inverted ERT and filtered radar sections revealed several resistivity and electromagnetic reflection anomalies that are identified laterally and vertically across the measured sections. These anomalies indicate the presence of fractures and karst features affected the limestone bedrock in the dam site. These near-surface karstified and fractured strata represent a critical hazard to the structural safety of the dam.

Spatial distribution and metal contamination in the coastal sediments of Al-Khafji area, Arabian Gulf, Saudi Arabia

To document the spatial distribution and metal contamination in the coastal sediments of the Al-Khafji area in the northern part of the Saudi Arabian Gulf, 27 samples were collected for Al, V, Cr, Mn, Cu, Zn, Cd, Pb, Hg, Sr, As, Fe, Co, and Ni analysis using inductively coupled plasma-mass spectrometer (ICP-MS). The results revealed the following descending order of the metal concentrations: Sr > Fe > Al > As > Mn > Ni > V > Zn > Cr > Cu > Pb > Co > Hg > Cd. Average levels of enrichment factor of Sr, As, Hg, Cd, Ni, V, Cu, Co, and Pb were higher than 2 (218.10, 128.50, 80.94, 41.50, 12.31, 5.66, 2.95, 2.90, and 2.85, respectively) and that means the anthropogenic sources of these metals, while Al, Zn, Cr and Mn have enrichment factor less than 2, which implies natural sources. Average values of Sr, Hg, Cd, Cr, Ni, and As in the coastal sediments of Al-Khafji area were mostly higher than the values recorded from the background shale and earth crust and from those results along coasts of the Caspian Sea and the Mediterranean Sea. The highest levels of Cu in the northern part of the studied coastline might be due to Al-Khafji desalination plant, while levels of Al, Ni, Cr, Fe, Mn, Pb, and Zn in the central part may be a result of landfilling and industrial sewage. The highest levels of As, Cd, Co, Cu, Hg, and V in the southern part seem to be due to oil pollutants from Khafji Joint Operations (KJO). The higher values of Sr in the studied sediments in general and particularly in locality 7 could relate to the hypersalinity and aragonitic composition of the scleractinian corals abundant in that area.

Hydrochemical equilibrium and statistical approaches as effective tools for identifying groundwater evolution and pollution sources in arid areas

Hydrochemical investigations, including geochemical analyses, multivariate statistics and geostatistics, were conducted to assess the factors that influence groundwater geochemistry and pollution potentiality in Luxor area, Upper Egypt. A total of thirty-one groundwater and surface water samples from the Quaternary aquifer and the River Nile were analyzed for fourteen physical and chemical variables for each sample. Spatial variations in total dissolved solids and nitrate concentration were mapped. Piper and Durov diagrams indicate that the hydrochemistry of groundwater is influenced by the secondary processes; mixing with fresh water from the River Nile and El Kalabia Canal, irrigation return flow, and sewage leakage, and reverse ion-exchange process. The hydrochemical modeling of mineral phase saturation indices shows that nearly all of the groundwater points are undersaturated with reference to calcite, aragonite, dolomite, anhydrite, gypsum, and halite. Correlation coefficients of the different variables are consistent with the saturation indices. Cluster analysis was used to identify four significant, distinct groundwater zones where the original groundwater was influenced differently by mixing processes. Factor analysis showed four mutually interfering factors reveal the chemical characteristics of the groundwater; these factors are caused by rock-water interactions, mixing of waters of different origins, and anthropogenic effects. Integration of hydrochemical and statistical analyses approach can be applied for the better management of water resources at a regional scale and in areas with comparable conditions.

Identification of hydrogeochemical processes and their influence on groundwater quality for drinking and agricultural usage in Wadi Nisah, Central Saudi Arabia

Groundwater quality of a region is often controlled by the geochemical processes that operate with respect to the aquifer-water interaction, especially in arid regions where rainfall recharge is minimal. The goal of the present research was to understand the hydrochemical processes influencing groundwater chemistry and to evaluate groundwater quality for drinking and agricultural usage in Wadi Nisah and Wadi Al-Awsat, south of Riyadh. Twenty-nine groundwater samples were analyzed for major physio-chemical parameters. Ionic plots, chloro-alkaline indices, and modified Piper plots point towards reverse ion exchange. Saturation indices and correlation coefficients indicate halite, calcite, and dolomite dissolution. The Piper plot shows that most of the groundwater samples (82.76%) are of the (Ca + Mg)–(Cl-SO4) type. The groundwater quality is not good for drinking due to its high total dissolved solid (TDS) content. The groundwater is found to be suitable for irrigation in terms of residual sodium carbonate, sodium adsorption ratio, soluble sodium percentage, Kelly’s index, and magnesium hazard. The high salinity is unsuitable for irrigation; however, this can be overcome by using salinity-resistant crop varieties.