缅甸皎漂农村地区饮用水源地土壤金属释放特征及水质安全策略

缅甸皎漂农村地区以水塘水为主要饮用水水源，此类水源普遍存在金属离子超标的问题.针对该问题，选取拟新建水塘选址地内不同深度的土壤样品，并对其进行理化指标、金属含量测定，同时对其进行浸泡及金属元素赋存形态提取实验.结果表明，土壤中除Ni元素含量超过农用地土壤污染风险筛选值外，其他金属元素含量均低于筛选值，且在垂直尺度空间上分布较均匀.通过浸泡实验发现，不同土层的浸泡液中Al、Fe、Mn、Ni元素浓度均超过了我国饮用水标准，其中，中层土（1.2~2.4 m）释放的金属离子浓度最高，释放速率最快，而深层土（>2.4 m）释放的Al、Fe、Ni离子较少.比较浸泡前后金属赋存形态发现，不同深度土壤中金属离子的释放与弱酸态、可氧化态含量变化有关，深层土中弱酸态Al、Fe、Ni释放量较少，同时通过弱酸态、可氧化态释放的金属离子被铁锰氧化物大量吸附转化为可还原态，所以其释放量低于浅层土（0~1.2 m）和中层土.Mn主要以弱酸态和可氧化态赋存于不同深度的土壤中，因此具有较高的迁移性.本文提出了以释放金属离子少的深层土作为水塘内壁的分质用土方案，以减少饮用水源金属离子释放风险，保障皎漂农村地区饮用水安全，并可为其他有类似饮用水问题的国家和地区提供参考.

Characteristics of metal release from the soil to drinking water sources and water safety strategies in rural areas of Kyaukpyu, Myanmar

Pond is the main source of drinking water in the rural areas of Kyaukphyu, and the excessive metal ions in pond water has been a long-term problem.To address this problem, samples taken from different depth of soil were analyzed to determine their physicochemical properties, metal contents, release characteristics and the formation of different metals in studied site. The result showed that the contents of all metals except Ni were not exceeding the standard values, and the distribution of different metals was identical in the vertical-scale. It was also found that Al, Fe, Mn and Ni in the soaking solution of different soil layers exceeded the drinking water standard in China, among which metal ions released from the middle layer of soil (1.2~2.4 m) showed the highest amount and releasing rate. However, the amount of Al, Fe, Ni ions released from deep soil (>2.4 m) were much lower than those from other layers of soil. Comparing the forms of metal before and after soaking, metal release was mainly determined by the content of acid extractable and oxidable form. The content of acid extractable Al, Fe and Ni in the deep soil is low, and the released ions can be highly adsorbed by iron and manganese oxides to transform into reducible form. Mn mainly exists in acid extractable and oxidizable state in soil at different depths, resulting in high mobility and bioavailability of Mn ions. According to the results, this paper proposes a measurement to release less metal ions by using the deep soil as the inner wall of the pond to protect drinking water sources and ensure the drinking water safety in Kyaukpyu rural areas. While it also provides countermeasures for the countries or regions with similar water problems.