新疆典型高砷地下水区域碘的空间分布特征及其影响因素分析

Characterizing the spatial distribution of iodine and analyzing its influential factors in a typical groundwater area with high arsenic content in Xinjiang

高碘、高砷地下水作为原生劣质地下水,具有区域性、伴生性和相似富集机理等特点.奎屯河流域是中国典型原生高砷水分布区,本研究基于奎屯河下游区域39组地下水水样,通过分析地下水水化学特征、赋存环境和水文地球化学过程,明确了该地区地下水中碘的分布特征与碘富集影响因素.结果表明:研究区地下水赋存环境为还原性弱碱性,I-浓度范围为13.96~574.85μg·L^(-1)(平均值为111.79μg·L^(-1)),38.46%的地下水为高碘地下水(ρ>100μg·L^(-1)),87.18%的地下水处于高砷环境(ρ>10μg·L^(-1)).地下水以低碘高砷地下水(53.85%)为主,其次为高碘高砷地下水(33.33%)、低碘低砷地下水(7.69%)、高碘低砷地下水(5.13%).地下水I^(-)浓度整体由南向北逐渐升高,高碘地区主要集中分布在研究区北部(126团、127团场、128团北侧靠近北山山前冲洪积砾土平原一带),占比为32.26%,适碘地区分布在研究区中部(128团场东部与南侧、127团和下游奎屯河南部),占比为38.40%,碘缺乏区域主要分布在研究区南部123团和129团,占比为29.33%.研究区地下水中铁氧化物还原性溶解和HCO_(3)^(-)与I^(-)的竞争吸附作用是影响地下水碘富集的主要因素,同时地下水中弱碱性还原环境、深厚的沉积层和滞缓的径流条件为碘的富集提供了有利的赋存环境和水文地质条件.

As the primary and inferior groundwater with both high iodine and arsenic has the characteristics of regional,concomitant and similar enrichment mechanism.Kuitun River basin is a typical primary high-arsenic water distribution area in China.Based on 39 sets of groundwater samples from the downstream area of Kuitun River,this study demonstrated the spatial distribution characteristics of iodine in groundwater in the region and the influential factors of iodine enrichment by analyzing the hydrochemical characteristics of the groundwater,the storage environment and the hydrogeochemical processes.The results showed that the groundwater storage environment in the study area was reductively and weakly alkaline,the Iconcentration ranged from 13.96 to 574.85 μg·L-1(the mean value was 111.79 μg·L^(-1)),and 38.46% of the groundwaters were high iodine groundwaters (ρ>100 μg·L^(-1)),while 87.18% of the groundwaters were in a high arsenic environment (ρ>10 μg·L^(-1)).The groundwater was dominated by low iodine and high arsenic groundwater(53.85%),followed by high iodine and high arsenic groundwater(33.33%),low iodine and low arsenic groundwater(7.69%),and high iodine and low arsenic groundwater(5.13%).The overall I-concentration of groundwater gradually increased from south to north,and the high iodine areas were mainly concentrated in the northern part of the study area(fields in 126 Regiment,127 Regiment,and the north side of 128 Regiment near the gravelly alluvial diluvial plain area in the front of Beishan Mountain),which accounted for 32.26%,and the iodine-suitable areas were distributed in the central part of the study area(east and south side of the field in 128 and 127 Regiments,and south of the downstream Kuitun River),which accounted for 38.40%,and the iodine-deficient areas were mainly distributed in the south of the study area in 123and 129 Regiments,accounting for 29.33%.The main factors influencing iodine enrichment in groundwater in the study area were the reductive dissolution of iron oxides and the competitive adsorption of HCO_(3)^(-)and I^(-),while the weakly alkaline reducing environment in the groundwater,the deep sedimentary layer and the slow runoff conditions provide a favorable environment for iodine enrichment and the hydrogeological conditions.