长江口滨岸浅层地下水化学组分时空分布特征及影响机制

Spatio-temporal distribution characteristics and mechanisms of chemical composition of shallow groundwater in coastal area of Yangtze River Estuary

为了解长江口滨岸浅层地下水化学特征,利用数理统计和水文地球化学分析方法对长江口南北两翼(上海浦东、江苏启东)和崇明岛东部的滨岸浅层地下水化学组分时空分布特征及其影响机制进行分析。结果表明:长江口滨岸浅层地下水在丰水期和枯水期分别为硬水极硬水和硬水,均以淡水为主;主要阳离子为Na^(+)和Ca^(2+),HCO_(3)^(-)为阴离子中含量最高组分;丰水期主要化学组分含量大于枯水期,且各个组分的空间变异值较枯水期大;与浦东滨岸相比,启东和崇明岛东部的滨岸浅层地下水化学类型季节性变化更明显;浅层地下水的主要补给来源为大气降水;长江口北翼和崇明岛东部区域浅层地下水主要受到土壤淋溶、岩石风化水解、阳离子交换作用和人为活动影响,同时在一定程度上受到蒸发浓缩作用的影响,仅个别点位受到海水混合作用的影响;长江口南翼主要受到岩石风化水解和阳离子交换作用的影响,基本不受海水混合作用的影响,农业活动对该区域影响较小。

In order to understand the chemical characteristics of shallow groundwater,using the coastal areas in Qidong City,Jiangsu Province on the north of the Yangtze River Estuary,the Pudong New Area,Shanghai on the south of the Yangtze River Estuary,and the eastern Chongming Island as the study areas,the spatio-temporal distribution characteristics and formation mechanisms of chemical composition of shallow groundwater were investigated with mathematical and statistical methods and hydrogeochemical analysis methods.The results show that the shallow groundwater in the coastal area of the Yangtze River Estuary was hard water-hardest water and hard water during the wet and dry seasons,respectively,and was mainly fresh water.The main cations were Na^(+)and Ca^(2+),and HCO_(3)^(-) was the anion with the highest content.The contents of main chemical components in the wet season were higher than those in the dry season,and the coefficient of spatial variation of each component in the wet season was larger than that in the dry season.Compared with Pudong,the chemical types of shallow groundwater in Qidong and the eastern Chongming Island showed a more significant seasonal change.The recharge of shallow groundwater mainly originated from atmospheric precipitation.The shallow groundwater in the coastal areas on the north of the Yangtze River Estuary and in the eastern Chongming Island were mainly affected by soil leaching,weathering and hydrolysis of rocks,cation exchange processes,and human activities,as well as evaporation and concentration to a certain extent,with only a few sites affected by seawater mixing.The coastal area on the south of the Yangtze River Estuary was mainly affected by weathering and hydrolysis of rocks and cation exchange processes and not affected by seawater mixing,and the agricultural activities had little influence on the area.