Geological Survey, China University of Geosciences, Wuhan 430074, China.
Lamont-Doherty Earth Observatory, Palisades, NY 10964, USA; Department of Earth and Environmental Sciences, Columbia University, New York, NY 10027, USA.
J Contam Hydrol. 2021 Dec;243:103894. doi: 10.1016/j.jconhyd.2021.103894. Epub 2021 Sep 25.
Iodine is an essential micronutrient in the human diet and an appropriate human iodine intake level is important for population health. Excessive iodine intake is often associated with high iodine groundwater which serves as an important drinking water source in many regions. This study aims to identify the source and key hydrogeochemical processes for iodine accumulation and mobility in the groundwaters of the Northern Jiangsu Yishusi Plain. Combined hydrogeochemical and statistical analyses, specifically random forest modeling and factor analysis, were used to explore the mechanisms affecting the spatial distribution of iodine. The concentration of iodine in the investigated groundwaters was found to vary widely and to range between 4.8 and 4750 μg/L, with 48.9% of the total samples (674) exceeding the threshold value of 100 μg/L for toxic exposure, as defined by the Chinese high‑iodine standard guideline. High iodine concentrations are shown to mainly occur in the marine plain and the shallow aquifer associated with the floodplains of the Old Yellow River. The marine or lagoons-facies sediments were identified as the most plausible iodine source. In addition, mixing of groundwater with paleo-seawater might also have played a role in the coastal area. In contrast, the flood sediments of the Old Yellow River are shown to be an unlikely source. However, they serve as a cover layer that favored the development of reducing hydrogeochemical conditions that can trigger iodine mobilization via the reductive dissolution of iron oxides and the degradation of organic matter. Slow groundwater flow rates also appear to favor iodine release from sediments.
碘是人体饮食中的必需微量元素，适当的人体碘摄入量对人口健康很重要。过量的碘摄入通常与高碘地下水有关，而高碘地下水是许多地区的重要饮用水源。本研究旨在确定苏北宜思寺平原地下水中碘的积累和迁移的来源和关键水文地球化学过程。结合水文地球化学和统计分析，特别是随机森林模型和因子分析，用于探讨影响碘空间分布的机制。研究发现，调查地下水中的碘浓度差异很大，范围在 4.8 至 4750μg/L 之间，总样本的 48.9%（674 个）超过了中国高碘标准指南中定义的有毒暴露阈值 100μg/L。高碘浓度主要出现在与古黄河泛滥平原相关的滨海平原和浅层含水层中。海洋或泻湖相沉积物被认为是最有可能的碘源。此外，地下水与古海水混合也可能在沿海地区发挥了作用。相比之下，古黄河洪水沉积物不太可能是碘的来源。然而，它们作为覆盖层，有利于还原性水文地球化学条件的发展，通过铁氧化物的还原溶解和有机物的降解触发碘的迁移。地下水流速缓慢似乎也有利于从沉积物中释放碘。
