Geochemistry of iodine-rich groundwater in the Taiyuan Basin of central Shanxi Province, North China

Abstract This paper presents the results of studies on the geochemistry of iodine-rich groundwater in the southwest of the Taiyuan Basin, Shanxi Province, North China. A total of 950 water samples were collected from shallow (≤ 50 m), medium-depth (50–200 m) and deep (≥ 200 m) wells in the southwestern Taiyuan Basin. Total and inorganic iodine concentrations, including species of iodide and iodate, were determined using inductively coupled plasma mass spectrometry (ICP-MS) and high performance liquid chromatography- ICP-MS (HPLC-ICP-MS). The results indicate that there are 76.8%, 70.3% and 85.2% of groundwater samples from the above-mentioned three levels, respectively, that exceed the national drinking water standard for iodine (150 μg/L), with the highest iodine concentration of up to 4117 μg/L, 27 times higher than the standard, tested in shallow groundwater. The main species of iodine in the groundwater is iodide ion with a small proportion of iodate. Organic iodine was detected in about 60% of the water samples with relatively low content. The main factors causing the high iodine concentrations in groundwater include the unique topography, geomorphologic features and aquifer structures in the study area, resulting in hindered movement of groundwater. Furthermore, salinization of surface soil in the low-lying lands intensifies the elevation of iodine concentrations in shallow groundwater. The enrichment of iodine in groundwater is inextricably linked to the geological environment of marine, lacustrine and fluvial sedimentations. The results of this research could provide scientific bases for optimization of water supply scheme in China's iodine excess areas.