长江三角洲北翼更新世以来的水土环境地球化学特征及其环境指示意义  

Geochemical characteristics of water and soil environment and its environmental indicating significances since the Pleistocene in the northern flank of the Changjiang River Delta

作　　者：苟富刚[1,2] 龚绪龙 刘源[1,2] Gou Fugang;Gong Xuong;Liu Yuan(Geological Survey of Jiangsu Province,Nanjing 210049,China;Key Laboratory of Earth Fissures Geological Disaster,Ministry of Natural Resources,Nanjing 210049,China)

机构地区：[1]江苏省地质调查研究院,江苏南京210049 [2]自然资源部地裂缝地质灾害重点实验室,江苏南京210049

出　　处：《海洋学报》2024年第3期33-53,共21页

基　　金：中国地质调查局项目(1212011220005);国家自然科学基金项目(42007402,41772327);江苏地质勘查项目(苏财资环[2022]27号)。

摘　　要：江苏沿海平原是江苏省域水资源脆弱带,地下水咸化已成为较为严重的生态环境问题。为了解析长江三角洲北翼地区更新世以来地下水的补给及其盐分来源,布设一口275 m的深井HYRD1,全孔连续采集易溶盐样品、土工样品、水样。在区域采集地表水、浅层与深层地下水、海水样品。采用易溶盐指标结合土工指标(含水率、湿密度、比重)获取了HYRD1高精度孔隙水的水化学特征。采用Piper三线图、Gibbs图、离子比值法等结合δD、δ^(18)O数据、^(14)C测年数据解析了更新世以来地下水的补给及其盐分来源。结果表明:土体盐分主要为NaCl,盐渍土占比为25%。盐渍土主要分布在Q_(p3)弱透水层、 Q_(p2)地层与Q_(p1)上段地层。孔隙水水化学类型为Cl-Na型(仅Q_(p1)下段个别点为HCO~-_3-Ca·Na),微咸水占比7%,咸水占比49%,盐水占比44%。微咸水主要分布在Q_(p1)下段砂层中。潜水的δ^(18)O、δD说明潜水来源为大气降水,且受到了较为强烈的蒸发作用。弱透水层孔隙水、承压水的δ^(18)O、δD投点位于标准海水稀释线附近,且随着深度的增加,δ^(18)O、δD有减小趋势,说明海水混合作用随着深度的增加而减小。Q_(p1)弱透水层多见钙质结核,说明了Q_(p1)地层成土后受到了强烈的蒸发作用。HYRD1 Q_(p1)上段及上覆地层盐分主要来源于5期海侵、蒸发盐岩与硅酸盐风化溶解,Q_(p1)下段地层盐分主要来源为地壳源。地下水化学成分受到了水岩作用、蒸发浓缩作用与人类活动等的影响。The coastal plain of Jiangsu Province is a fragile zone of water resources in Jiangsu Province,and groundwater salinization has become a serious ecological problem.In order to analyze the groundwater recharge and its salinity sources in the north flank of the Changjiang River Delta since Pleistocene,a 275 m deep well HYRD1 was deployed and the whole hole was continuously collected with easily soluble salt samples,geotechnical samples and water samples.Surface water,shallow and deep groundwater,and seawater samples were collected in the area.The hydrochemical characteristics of Well HYRD1 high-precision porewater were obtained by using sol-uble salt index combined with geotechnical index(water content,wet density,specific gravity).In order to analyze the groundwater recharge and its salt source since Pleistocene,Piper trilinear diagram,Gibbs diagram and ion ratio method were used in combination withδD andδ^(18)O data and ^(14)C data.The results show that the salinity of Well HYRD1 soil is mainly NaCl,and the percentage of saline soil is 25%.The saline soils are mainly distributed in the Q_(p3) aquitard,Q_(p2) stratum and the upper part of Q_(p1) stratum.The water chemistry type of porewater is Cl-Na type-3(only the lower section of Q_(p1) is HCO-Ca·Na at individual points),7%of brackish water,49%of saline water and 44%of haline water.The brackish water is mainly distributed in the sand layer of the lower section of Q_(p1).Theδ^(18)O and δD of diving indicate that the source of diving is atmospheric precipitation and is subject to a relatively strong evaporation effect.The δ^(18)O andδD of the aquitard pore water and pressurized water are located near the standard seawater dilution line,and the trend of δ^(18)O andδD decreases with the increase of depth,which indicates that the porewater is subjected to the mixing effect of seawater decreases with the increase of depth.Calcareous nodules are mostly seen in the Q_(p1) aquitard,indicating that the Q_(p1) aquitard was subjected to strong evaporation after soi

关 键 词：沉积环境 含盐特征 易溶盐 孔隙水 弱透水层 沿海含水层 

分 类 号：P736.4[天文地球—海洋地质]