长江口北翼海滨地区海水入侵的地球化学特征初步研究

Preliminary study in geochemical characteristics of seawater intrusion in the coastal region north wing of the Yangtze River Estuary

利用2009年2月和8月两次在长江口北部滨海地区地下水调查取得水化学数据,综合运用数理统计法、Piper三线图法,分析长江口北翼滨海平原海水入侵区浅层地下水的地球化学特征,识别不同季节浅层地下水水化学类型的特征。研究结果表明:(1)研究区地下水主要靠大气降水及地表水体渗透补给,季节变化对区域内地下水水化学空间变异性影响较大。(2)Na+、K+、Cl-变异系数较大,而HCO3-、CO32-绝对含量大,它们是决定海滨海水入侵地区地下水水化学类型的主要离子。(3)由陆向海方向,区域内水化学类型由主要从Mg-Ca-HCO3、Na-Mg-HCO3型经Mg-Ca-HCO3-Cl、Na-HCO3-Cl型向Na-Cl-SO4、Na-Cl型演变;大气降水、水-岩离子交换、残存海水上移、海陆地下水交互作用是控制地下水演变的主要因素。

According to the investigation of water chemistry data in the northern coastal region of the Yangtze River Estuary both in August and February of 2009 by Second Institute of Oceanography,through comprehesively using the mathematical statistics method and the Piper Method,the paper completely analyzed the chemical characteristics of shallow groundwater in the Yangtze River Estuary,North Wing,and identified the water chemistry of shallow groundwater impact in different seasons.The results show that：（1） groundwater mainly depends on the supply of precipitation and surface water infiltration recharge;seasonal changes has greater impact on the spatial variability in water chemistry of groundwater in the region of the study area.（2） Na ＋ ＋ K ＋,Cl-has greater coefficient of variation,but HCO3-＋CO32-has absolutely content in large,and they are all to determine major ion water chemistry types in the coastal seawater intrusion of groundwater.（3） from the coastside to land,the chemical type of water mainly turns from the Mg-Ca-HCO3,Na-Mg-HCO3 type by Mg-Ca-HCO3-Cl,Na-HCO3-Cl type to Na-Cl-SO4,Na-Cltype evolution;atmospheric precipitation,water-rock ion exchange,residual water moving and the interaction of groundwater and sea are the main factors controlling the evolution of groundwater.