江汉平原东北部地区高铁锰地下水成因与分布规律

肖港地区位于江汉平原东北部，属于大别山连片贫困区和贫水区，地下水资源较贫乏，且地下水水质不佳，水中铁锰离子含量普遍超过了国家饮用水标准。为查明高铁锰地下水成因及空间分布规律，服务区内地下水开发利用及安全供水问题，系统采集区内岩石、土壤和地下水样品，测试岩土与地下水中铁锰的含量，分析地下水中铁锰含量与含水层沉积物的铁锰含量、地下水的氧化还原条件和酸碱度之间的关系。结果表明:江汉平原东北部地区地下水中铁锰超标现象普遍存在，其中锰的超标率大于铁，第四系孔隙潜水超标最严重，铁锰最大浓度分别达到44.88 mg/L和19.21 mg/L。研究区岩土中铁锰氧化物为地下水中铁锰提供了物质来源，弱酸性、强还原环境为沉积物中铁锰的溶解释放提供了有利条件，总体上从研究区东西两侧（补给、径流区）向中部第四系孔隙潜水含水层（排泄区），沿地下水流向Eh值、pH值逐渐减小，铁锰含量逐渐增大，形成北北东向带状分布的高铁锰地下水区。

Distribution and genesis of high Fe and Mn groundwater in the northeast of the Jianghan Plain

The Xiaogang region is located in the northeastern Jianghan Plain, and it belongs to the contiguous poverty-stricken areas and water-scarce areas of the Dabie Mountains. The groundwater resource is relatively rare and the groundwater quality is not good. The contents of iron and manganese in the water generally exceeds the national drinking water standard. In order to find out the genesis and spatial distribution of high iron and manganese groundwater, service the development and utilization of groundwater and the problem of water supply safety in the area, we systematically collected the rock, soil, and groundwater samples to test the iron and manganese contents, analyzed the relationship between the contents of iron and manganese in groundwater and the contents of iron and manganese in aquifer sediments, the redox conditions, and pH environment of groundwater. The results show that excessive iron and manganese in groundwater is widespread in the northeastern Jianghan Plain. Among them, the over-standard rate of manganese is greater than that of iron, and the Quaternary pore phreatic groundwater is the worst, with the maximum concentrations of iron and manganese reaching 44.88 mg/L and 19.21 mg/L, respectively. Iron and manganese oxides in rock and soil in the study area, providing material sources for iron and manganese in groundwater. The weak acidity and strong reduction environment provide favorable conditions for the dissolution and release of iron and manganese in sediments. In general, from the east-west sides of the study area (recharge and runoff areas) to the Quaternary pore aquifer (discharge area) in the middle of the study area, the Eh value and pH value along the groundwater flow direction gradually decrease, and the contents of Fe and Mn gradually increase and eventually form a northward high iron-manganese groundwater zone.