Elemental and radiological aspects of geothermal springs and nearby soil and sediment of Al-Lith area: Concentration and risk assessment
Khater, Mohamed H.E. Monged, Mohamed T. Hussein, Ashraf E.M. . 2018
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) were 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 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 were evaluated by comparing the elemental concentration of the water samples to the maximum contaminant level (MCL) of USEPA and WHO for drinking water. The elemental concentration of water samples were 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 still below unity. The average activity concentration in Bq kg-1of 228Ra (232Th series), 40K and 137Cs were 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.
Keywords: Geothermal springs; Element; Natural radionuclides; gamma spectrometry; Al-Lith, Saudi Arabia; Risk assessment.
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