江汉平原汉江带地下水水化学特征分析

Hydrochemical Characteristics of Groundwater of the Hanjiang Zone in the Jianghan Plain

为研究江汉平原汉江带地下水水化学特征,调查并采集了区内浅层(深度0~20 m)、中层(深度20~80 m)、深层(深度>80 m)地下水样品共552个以及地表水样品61个,通过对该地区不同层位地下水样品进行水化学组分测试,并运用Piper三线图、数理统计、相关性分析等方法揭示了江汉平原汉江带不同层位地下水水化学特征及其空间分布规律。结果表明:江汉平原汉江带地表水和地下水的水化学类型以HCO3-Ca(Mg)型为主;地下水的pH值范围为6.9~8.2,TDS含量范围为117.5~1 644 mg/L,且垂向分层现象明显,表现为浅层地下水>中层地下水>深层地下水;该地区浅-中层地下水中Cl^-、SO4^2-、NO3^-质量浓度存在空间差异性;中层地下水赋存环境显示丘陵地区基本属于氧化环境,而平原区为还原环境;依据饮用水水质标准,区内劣质地下水中Fe、Mn、As含量超标率较高;沙洋县以北平原区中层地下水中F含量偏高,超标数占比高达96.5%;研究区地下水水质主要受农业灌溉、生活污水排放和天然地质条件的影响,但沿地下水径流方向,地下水水质逐渐变好。

To find out the hydrochemical characteristics of groundwater of the Hanjiang zone in the Jianghan Plain,this paper collects 552 groundwater samples from the shallow(depth 0-20 m),middle layer(depth 20-80 m),deep layer(depth >80 m) groundwater and 61 surface water samples,analyzes the groundwater chemical components,and uses the Piper diagram,mathematical statistics and correlation analysis methods to reveal the geochemical characteristics and spatial distribution of groundwater in different layers.Results show that the chemical types of surface water and groundwater in the Hanjiang zone are mainly HCO3-Ca(Mg).Groundwater pH value ranges from 6.9 to 8.2,and TDS ranges from 117.5 to 1 644 mg/L with obvious vertical stratification,namely,TDS in shallow groundwater>middle layer groundwater>deep layer groundwater.There are spatial differences in concentration of Cl^-,SO4^2- and NO3^- in shallow and middle layer groundwater.The storage environment of the middle layer groundwater shows that groundwater in the hilly area is almost oxidization environment,while the plain area is reducing environment.According to the drinking water quality standards,the main indicators of poor quality groundwater in the area are Fe,Mn,As;in addition,the fluoride content is relatively higher in the middle layer groundwater in the plain area,north of Shayang County,where the proportion of exceeding the standard is as high as 96.5%.The groundwater quality in the study area is affected by agricultural irrigation,domestic sewage discharge,and natural geological conditions.However,along the direction of groundwater flow,the groundwater quality gradually improves.