Geochemical characteristics of water and soil environment and its environ-mental indicating significances since the Pleistocene in the northern flank of the Changjiang River Delta
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 with δD and δ18O data and 14C 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 Qp3 aquitard,Qp2 stratum and the upper part of Qp]stratum.The water chemistry type of porewater is Cl-Na type(only the lower section of Qp1 is HCO3-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 Qp1.The δ18O and 8D of diving indicate that the source of diving is atmospheric precipitation and is subject to a relatively strong evaporation effect.The δ18O and δD of the aquitard pore water and pressurized water are located near the standard seawater dilution line,and the trend of δ18O and δD 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 Qp1 aquitard,indicating that the Qp1 aquitard was subjected to strong evaporation after soil forma-tion.The salinity of the upper part of Well HYRD1 Qp1 and the overlying strata is mainly from the 5th stage sea erosion,evaporite and silicate weathering dissolution.The salinity of the lower part of Qp1 is mainly from the crustal source.The groundwater chemistry is influenced by water-rock action,evaporation concentration and hu-man activities.
万方数据
维普
