江汉平原高砷地下水区地下水的化学特征及指示

Study on the chemical characteristics of groundwater and instructions of high arsenic groundwater at Jianghan Plain

以江汉平原中部的仙桃市、洪湖市2个砷中毒病区作为典型研究区,每处分别取了30户手压井水样,通过对样品中As浓度的分析、测试,并结合分析水样总溶解固体（TDS）、pH、氧化还原电位（ORP,以Eh表征）、SO42-、NO3-、Cl-、HCO3-、Fe、Mn等指标,探讨了地下水中As浓度与化学指标间的相关性.结果表明,所取60份水样中,As质量浓度最高值为1.560 mg/L,超过0.05mg/L的有17份水样,超标率为28％;研究区地下水pH为6.01～7.16,平均为6.56,明显偏酸性,Eh为13.6～75.3 mV,平均为44.2 mV,呈弱氧化性,该结果与中国山西大同盆地、山阴地区、内蒙古河套平原等原生高砷水地区有着明显的差异;水样的As浓度与TDS、HCO3-、Fe、Mn浓度呈正相关,与SO42-、NO3-浓度呈负相关,研究区地下水环境是典型的高砷水赋存环境;水样中TOC质量浓度为2.35～5.32 mg/L,平均为3.29 mg/L,溶解性有机物对水体中As的迁移转化有着很重要的作用.

30 groundwater samples were collected respectively from two endemic arsenism areas of Xiantao and Honghu,they were located in the central Jianghan Plain, H ubei Province. The groundwater chemical characteristics, including the contents of arsenic, TDS, pH, Eh, SO4^2- , NO3^- , Cl^- , HCO3^- , Fe and Mn, of these samples were measured and compared to study the relationship between arsenic and the other measured parameters. Among the 60 groundwa- ter samples,the maximum arsenic concentration was 1. 560 mg/L,28% ground water samples （17 samples） exceeded the specified limits （0.05 mg/L） of drinking water. The pH of ground water samples ranged 6.01-7.16 with average p H was 6.56, suggesting an obvious acidity of groundwater~ the Eh of these samples ranged 13.6-75.3 mV, the aver- age Eh was 44.2 mV,appearing weak oxidation. These water chemical characteristics showed a significant difference compared with the groundwater from Datong Basin, Shanxi Shanyin and Hetao Plain of Inner Mongolia. A positive correlation was observed between As and TDS, HCO3^- , Fe, Mn. However, a negative correlation was found between As and SO4 ^2- , NO3^- , which suggests the typical environment of high arsenic in groundwater. TOC of these groundwa- ter samples ranged 2.35-5.32 mg/L with the average value was 3.29 mg/L,the dissolved organic matters played the key role in transportation and transformation of arsenic in groundwater.