扬泰靖地区地下水硫同位素组成特征及其意义

Characteristics of sulfur isotope in groundwater of the Yangzhou-Taizhou-Jingjiang Area

通过分析长江三角洲扬泰靖地区第四系松散层地下水硫酸盐的硫同位素组成特征,揭示不同层次和地段地下水中硫酸盐的演化规律及其赋存环境变化特点。研究表明潜水中硫同位素值变化不大,8.3‰～10.5‰,而孔隙承压水中硫同位素值变化较大,随深度增加而增大(最高达71.6‰)。在潜水中,硫酸盐源于农业污染或污染物与海源硫酸盐的混合;在顶部地区和沿江地段的浅层孔隙承压水中,负δ34S值的硫酸盐源于硫化物的氧化,与其松散层岩性以砂性土为主、径流条件好、封闭性差和处于氧化环境有关;而在东部的深层孔隙承压水中,高δ34S值的硫酸盐源于硫酸盐的还原,与其松散层岩性以粘性土为主、隔水层发育、径流条件差、封闭性好和处于还原环境有关。

Through analyzing the characteristics of sulfur isotope of sulfate in groundwater in the Quaternary unconsolidated soils of the Yangzhou-Taizhou-Jingjiang area,the evolution and variation of the occurrence environment of sulfate in groundwater at different depths and sites are discussed in this paper.The results indicate that δ34S values of sulfate in the phreatic water range from 8.3‰ to 10.5‰ with a slight change,but the δ34S values of sulfate in the confined aquifer vary significantly and increase with increasing depth（up to 71.6‰）.In the phreatic aquifer,sulfate originates from agricultural pollution or a mixture of pollutants with marine sulfates;in the shallow confined aquifer along the Yangtze River and at the top of the study area,sulfate with negative δ34S values originates from oxidation of sulfides,which is related to the sand-dominated lithologic characteristics,good runoff conditions,poor sealing property and aerobic environment;in the deep confined aquifer of eastern area,sulfate with higher δ34S values originates from reduction of sulfates,which is related to the clay-dominated lithologic characteristics,poor runoff conditions,good sealing property and anaerobic environment.Variation of the occurrence environment of sulfate in groundwater at different depths and sites are further verified by the corresponding chemical characteristics of groundwater.