Hydrogeochemistry of high iodine groundwater: a case study at the Datong Basin, northern China
Abstract
High iodine concentrations in groundwater have seldom been reported and there have been few systematic studies on high iodine groundwater worldwide. To better understand the sources and processes responsible for iodine enrichment in the groundwater of the Datong Basin, the hydrochemical characteristics of groundwater and geochemical features of aquifer sediments were studied. High iodine groundwater mainly occurs in the center of the Datong Basin with iodine concentrations ranging between 3.31 and 1890 μg L−1. Most samples with iodine concentrations higher than 500 μg L−1 are from wells with depths between 75 and 120 m. High pH and a reducing environment are favorable for iodine enrichment in the groundwater, with iodide as the dominant species that accounts for 63.2–99.3% of the total iodine. Sediment samples from a borehole specifically drilled for this study contain 0.18–1.46 mg kg−1 iodine that is moderately correlated with total organic carbon (TOC). The results of sequential