大同盆地地下水中碳硫同位素组成特征及其对碘迁移富集的指示  

Carbon and Sulfur Isotopic Features and Its Implications for Iodine Mobilization in Groundwater System at Datong Basin, Northern China

作　　者：朱沉静 李俊霞[1,2] 谢先军[1,2] Zhu Chenjing;Li Junxia;Xie Xianjun(School of Environmental Studies,China University of Geosciences,Wuhan 430078,China;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Wuhan 430078,China)

机构地区：[1]中国地质大学环境学院,湖北武汉430078 [2]中国地质大学生物地质与环境地质国家重点实验室,湖北武汉430078

出　　处：《地球科学》2021年第12期4480-4491,共12页Earth Science

基　　金：国家自然科学基金项目(Nos.42020104005,41502230)。

摘　　要：为深入探究地下水系统中影响碘迁移转化的主控水文生物地球化学过程,对大同盆地典型高碘地下水区完成样品采集,分析地下水样品基础理化性质及碳硫同位素组成特征.结果表明,大同盆地地下水碘含量变化范围为14.40~1030.00μg/L,高碘地下水(I>100μg/L)主要分布在盆地中心排泄区.地下水中溶解性无机碳的δ13C_(DIC)值变化范围为-12.11‰~-9.79‰,硫酸盐δ^(34)S_(SO4)值介于4.04‰~16.63‰.δ^(13)C_(DIC)和DOC之间存在较明显的正相关关系,表明有机质的微生物降解过程是区域地下水无机碳的重要来源之一.同时,δ^(13)C_(DIC)与δ34S_(SO4)一定的负相关关系表明硫酸盐是有机质微生物降解过程中潜在电子受体之一,且地下水水环境以偏还原环境为主.高碘地下水表现出低δ13C_(DIC)、高δ^(34)S_(SO4)的同位素特征,表明有机质的微生物降解过程是控制地下水中碘迁移释放的主要过程之一,与该过程相伴而生的碘形态转化进一步促使碘以碘离子的形式在偏还原的地下水环境中发生富集.In order to understand the dominant hydro-biogeochemical processes affecting the migration and transformation of iodine in groundwater system,in this study it analyzed the chemistry and carbon/sulfur isotope signatures of groundwater samples from typical high iodine area in Datong basin.Results show that the iodine concentrations of groundwater range from 14.40 to 1030.00μg/L and high iodine groundwater(I>100μg/L)is mainly distributed in the discharge area near the center of the basin.The δ34S_(SO4) and δ13C_(DIC) signatures of groundwater have the ranges of(-12.11‰)-(-9.79‰)and 4.04‰-16.63‰,respectively.The positive correlation between theδ13CDICvalues and DOC concentrations in groundwater suggests that microbial degradation of organic matter is one of the important sources of DIC in the Datong basin.The correlation between the lowδ13C_(DIC)values and the high δ34S_(SO4)values indicates that groundwater SO_(4)^(2-)serves as one of the electron accepters during the biodegradation of organic matter,and groundwater environment was dominant by the weak reducing conditions.High iodine groundwater is characterized by lowerδ13C_(DIC) and higher δ34S_(SO4),indicating that microbial degradation of organic matter,which acts as a dominate host of sediment iodine,promotes the release of iodine into groundwater.Moreover,the transformation among iodine species,for instance,from organic iodine/iodate to iodide,also favors the enrichment of groundwater iodine under the reducing conditions.

关 键 词：碘 地下水 大同盆地 碳硫同位素 迁移释放 水文地质学 

分 类 号：P641[天文地球—地质矿产勘探]