【作者】 孙英；

【导师】 周金龙；

【作者基本信息】 新疆农业大学 ， 水利工程， 2022， 博士

【摘要】 塔里木盆地是我国西北典型的内陆干旱盆地,由于地表水资源稀缺,地下水是维持该区人类生存与发展和生态系统平衡的重要水源。盆地内绿洲带地下水质量总体较差,生态环境十分脆弱,严重威胁当地用水安全。前期研究显示,该区分布有高碘地下水,危害人体健康。因此,系统地查明该区地下水碘的分布及成因至关重要。本文以塔里木盆地绿洲带为研究区,以绿洲带高碘地下水为研究对象,分析不同区域（补给区、过渡区和蒸发区）、不同含水层（单一结构潜水、承压水区潜水、浅层承压水和深层承压水）中高碘地下水的空间分布和水化学特征,运用相关性分析、因子分析和聚类分析方法,对高碘地下水的形成进行了分析。综合绿洲带地质、水文地质条件、地下水赋存环境及水文地球化学作用确定地下水中碘的来源及影响碘富集的主要成因。选取典型高碘地下水区域加密取样,以获取水化学、氘氧同位素、碘形态、Cl/Br摩尔比值等数据,进一步揭示地下水中碘的来源与碘富集机理。主要研究成果如下:（1）绿洲带地下水碘含量变化范围为<20.0～4000.0μg/L,均值为53.7μg/L。高碘地下水（碘含量>100.0μg/L）水样占7.3%。典型区地下水碘含量变化范围为<40.0～435.0μg/L,均值为123.5μg/L,高碘地下水水样占50.0%。典型区地下水碘元素的存在形态主要为I^-（87.5%）,其次为IO₃^-（12.5%）,且无共存形态,亚氧化环境和亚还原环境分别利于碘元素以IO₃^-和I^-形态存在。（2）绿洲带地下水碘含量自补给区至过渡区,再至蒸发区逐渐增大,高碘水水化学类型以SO₄·Cl型和Cl型水为主。高碘地下水主要分布于绿洲带东南部的巴音郭楞蒙古自治州若羌县和尉犁县、西部阿克苏地区的库车县、西南部喀什地区的疏勒县,部分分布于南部和田地区民丰县和西南部喀什地区的英吉沙县。地下水碘含量在浅层承压水中最高,其次为单一结构潜水和承压水区潜水,深层承压水中碘含量普遍较低。（3）绿洲带高碘型地方性甲状腺肿潜在发病率为5.0%～49.1%。过渡区较蒸发区高碘型地方性甲状腺肿潜在发病率低（潜在发病率均值分别为14.2%和31.5%）;浅层承压水较单一结构潜水和承压水区潜水高碘型地方性甲状腺肿潜在发病率高（潜在发病率均值分别为24.9%、9.5%和5.7%）。库车县、尉犁县、若羌县、轮台县、民丰县高碘型地方性甲状腺肿潜在发病率较高（潜在发病率均值分别为36.5%、28.8%、24.1%、16.7%和10.6%）。（4）第四纪成因类型中洪积—湖积物为绿洲带地下水碘的富集提供了来源。冲积—湖积物为典型区承压水碘的富集提供了来源。地下水中的碘受铁（氧）氢氧化物矿物的还原性溶解作用和有机质的微生物降解作用的影响。细粒岩土、平缓的地势、地下水浅埋条件及弱还原环境均有利于地下水碘的富集。浅层高碘地下水受蒸发作用、蒸发盐岩风化溶解的影响较大,且高碘地下水中岩盐的溶解状态更趋于平衡。（5）典型区地下水碘含量与δD、δ18O值关系表明高碘地下水受蒸发作用明显大于低碘水。Cl^-与Cl/Br摩尔比值表明地下水主要受岩盐溶解作用。地下水溶解性有机碳含量整体较低,碘含量与溶解性有机碳含量间的相关性不显著。（6）绿洲带高碘地下水占比大于5%的流域的地下水碘含量与Na⁺、Cl^-、SO₄^2-、TDS和TH间为指数拟合时效果较好,依据所建立的拟合方程确定了不同流域对应高碘地下水（碘含量为100μg/L）的各指标的临界值。更多还原

【Abstract】 Tarim basin is a typical inland arid basin in northwest China.Due to the scarcity of surface water resources,groundwater is an important water source to maintain human survival and development and ecosystem balance in this area.The groundwater quality of oasis in the basin is generally poor,and the ecological environment is very fragile,which seriously threatens to local water security.Previous studies have shown that high iodine groundwater is distributed in this area,which is harmful to human health.Therefore,it is very important to systematically identify the distribution and genesis of iodine in groundwater.The oasis zone of Tarim Basin is taken as the study area,and the high-iodine groundwater in the oasis zone is taken as the research object.The spatial distribution and hydrochemical characteristics of high-iodine groundwater in different regions（recharge zone,transition zone and evaporation zone）and different aquifers（single-structure unconfined groundwater,unconfined groundwater in confined water area,shallow confined water and deep confined water）are analyzed.The formation of high-iodine groundwater is analyzed by correlation analysis,factor analysis and cluster analysis.The sources of iodine in groundwater and the main causes affecting iodine enrichment were determined by combining geological,hydrogeological conditions,groundwater occurrence environment and hydrogeochemical effects of oasis zone.The typical high-iodine groundwater area was selected for intensive sampling to obtain the data of hydrochemistry,deuterium oxygen isotope,iodine morphology,Cl/Br molar ratio,and further reveal the source of iodine in groundwater and iodine enrichment mechanism.（1）The iodine content of groundwater in oasis belt varies from<20.0μg/L to 4000.0μg/L,with an average of 53.7μg/L.7.3%of high iodine groundwater samples（iodine content>100.0μg/L）.The iodine content of groundwater in typical areas ranged from<40.0μg/L to 435.0μg/L,with an average of 123.5μg/L,and high iodine groundwater samples accounted for 50.0%.The main forms of iodine in groundwater in the typical area is mainly I^-（87.5%）,followed by IO₃^-（12.5%）,and there is no coexistence form.Sub-oxidation environment and sub-reduction environment are conducive to the existence of iodine element in IO₃^-and I^-forms,respectively.（2）The groundwater iodine content in oasis belt increases gradually from recharge zone to transition zone and then to evaporation zone,and the hydrochemical types of high iodine water are mainly SO₄·Cl and Cl.The high iodine groundwater is mainly distributed in Ruoqiang County and Yuli County of Bayingolin Mongolian Autonomous Prefecture in the southeast,Kuche County of Aksu Prefecture in the west,Shule County of Kashgar Prefecture in the southwest,and part of it is distributed in Minfeng County of Hetian Prefecture in the south and Yingjisha County of Kashgar Prefecture in the southwest.The groundwater iodine content is highest in shallow confined water,followed by single-structure unconfined groundwater and unconfined groundwater in confined water area,and is generally lower in deep confined water.（3）The potential incidence of high-iodine endemic goiter in the oasis zone ranged from 5.0%to49.1%.The potential incidence of high-iodine endemic goiter was lower in the transition zone than that in the evaporation zone（mean potential incidence 14.2%and 31.5%,respectively）.The potential incidence of high-iodine endemic goiter in shallow confined water was higher than that in single-structure unconfined groundwater and unconfined groundwater in confined water area（mean potential incidence 24.9%,9.5%and 5.7%,respectively）.The potential incidence of high-iodine endemic goitre was higher in Kuche County,Yuli County,Ruoqiang County,Luntai County and Minfeng County（mean potential incidence values were 36.5%,28.8%,24.1%,16.7%and 10.6%,respectively）.（4）Among the Quaternary genetic types,alluvial-lacustrine deposits provide the source of iodine enrichment in groundwater of oasis zone.Alluvial-lacustrine deposits provide a source of iodine enrichment in confined water in typical areas.Groundwater iodine was influenced by reductive dissolution of iron（oxy）hydroxide minerals and microbial degradation of organic matter.Fine-grained rocky soils,gentle topography,shallow groundwater burial conditions and weakly reducing environment are all conducive to groundwater iodine enrichment.Shallow high iodine groundwater is more influenced by evaporation,weathering dissolution of evaporated salt rock,and the dissolution state of rock salt in high iodine groundwater is more equilibrium.（5）The relationship between groundwater iodine content andδD andδ¹⁸O values in typical areas showed that high iodine groundwater was significantly more affected by evaporation than low iodine groundwater,and the Cl^-and Cl/Br molar ratio indicated that groundwater was mainly subject to rock salt dissolution.The overall dissolved organic carbon content of groundwater was low and the correlation between iodine content and dissolved organic carbon content was not significant.（6）The exponential fit between groundwater iodine content and Na⁺,Cl^-,SO₄^2-,TDS and TH in the basins with high iodine content of more than 5%in the oasis belt is better.The critical values of each index corresponding to high iodine content of groundwater（iodine content of 100μg/L）in different basins are determined according to the established fitting equation.更多还原