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Elemental and radiological aspects of geothermal springs and nearby soil and sediment of Al-Lith area: concentration and risk assessment

Monged, MohamedH. E., Hussein, MohamedT., Khater, AshrafE. M.
Environmental earth sciences 2018 v.77 no.12 pp. 427
United States Environmental Protection Agency, World Health Organization, anions, arsenic, bedrock, cadmium, cations, cesium, drinking water, electrical conductivity, environmental impact, gamma radiation, germanium, hot springs, iron, lead, maximum contaminant level, mercury, molybdenum, nickel, pH, pollution load, potassium, radionuclides, radium, risk, risk assessment, sediments, soil, spectrometers, strontium, temperature, thorium, toxicity, uranium, water quality, zinc, Saudi Arabia
Due to the interaction of water with hot deep bedrock within the geothermal system, the geochemical, elemental and radiological aspects of water and nearby soil and sediment samples are essential to investigate the water quality and the potential ecological impacts on the nearby area. In this study, four geothermal water springs located within Al-Lith region, Saudi Arabia, (namely Al-Harra, Bani Hilal, Markoub and Daraka) have been investigated. In addition to 9 water samples, 15 soil and sediment samples were collected from the adjacent areas. Some physicochemical parameters of water samples such as major anions and cations, pH, EC, and temperature were measured. The concentration of some toxic and other elements such as As, Cd, Ni, Pb, Th, U, and Zn, as well as some natural radionuclides [e.g.²²⁶Ra (²³⁸U series), ²³²Th series, ⁴⁰K] and the artificial radionuclide (¹³⁷Cs) was measured using ICP-MS and gamma-ray spectrometer based on hyper-pure germanium detector. The ecological impacts of the discharged water were evaluated using pollution and risk indices such as enrichment factor (EF), geo-accumulation index (Igₑₒ), contamination factor (CF), degree of contamination (Cd), pollution load index (PLI) and potential ecological risk index (RI). The water quality was evaluated by comparing the elemental concentration of water samples to the maximum contaminant level (MCL) of USEPA and WHO for drinking water. The elemental concentration of water samples was below the MCL except for Fe and As. Pollution and risk indices for soil and sediment samples revealed that there was a slight enrichment of Sr and Mo in three locations and considerable contamination with Hg in one location. However, the pollution load index was still below unity. The average activity concentration in Bq kg⁻ ¹of ²²⁸Ra (²³²Th series), ⁴⁰K and ¹³⁷Cs was within their world average values, while that of ²²⁶Ra (²³⁸U series) was slightly higher, which could be due to its accumulation from geothermal water to soil and sediment matrices.