Hydrogeochemical Characteristics and Health Effects of Iodine in Groundwater in Wei River Basin

Abstract

Existing studies show that drinking high-iodine or low-iodine groundwater on a long-term basis may cause goiter and other health problems. However, currently there is a lack of systematic research on the distribution, formation and health effects of iodine in groundwater at the basin scale. Taking the Wei River Basin in the Loess Plateau as a typical study area, this paper used hydrogeological surveys, sample collection, multivariate statistical analysis, health effect evaluations, and other methods, and found that iodine content in groundwater in 60.3% of the region poses potential risks to human health. Groundwater recharge areas were iodine-deficient, mainly located on the upstream Loess Plateau of the Wei River Basin in the vicinity of the Liupan Mountain watershed, and at the piedmont of the Qinling Mountains. Groundwater was low mineralization, neutral, and low-F bicarbonate, and was controlled by the weathering and dissolution of silicate minerals and evaporites, the dissolution and precipitation of carbonates, and active water circulation conditions. Iodine-deficient endemic goiter had a potential incidence of 5–38% in these areas. Groundwater runoff areas had suitable groundwater iodine content, and the groundwater hydrochemical type was dominated by HCO3–Ca, HCO3–Na, and HCO3·SO4–Na type water. The mineralization degree was modest and the I− content distribution of suitable iodine content areas was controlled by relatively active water circulation conditions. Groundwater discharge areas were high-iodine groundwater areas, where the groundwater hydrochemical type was dominated by meta-alkaline and alkaline HCO3·SO4, SO4·Cl, and Cl·SO4 type water, and controlled by the evaporation–concentration of shallow groundwater, the biodegradation of enriched organic matter, and the competitive adsorption of HCO3− and I−. Here iodine-excess endemic goiter had a potential incidence of 5–100%. Considering the results from the study area, this paper recommends that the groundwater iodine safety range for endemic goiter be set to 10.0–300.0 μg/L.