吉兰泰盐湖盆地地下水Cr^(6+)、As、Hg健康风险评价

Health risk assessment of Cr^(6+), As and Hg in groundwater of Jilantai salt lake basin, China

选取西北干旱区吉兰泰盐湖盆地为研究对象,系统采集71个地下水样品,测定重金属Cr^(6+)、As、Hg,以及主要化学成分的含量,以地质统计学插值绘图揭示盐湖盆地地下水中Cr^(6+)、As、Hg的空间分布特征,以单因子指数法、内梅罗指数法和US EPA健康风险评价模型解析地下水中Cr^(6+)、As、Hg的污染及健康风险状况,以统计相关检验进行Cr^(6+)、As和Hg的源分析.结果表明:盐湖盆地地下水中普遍含有Cr^(6+)、As、Hg,Cr^(6+)在盐湖上游及东北部含量较高,As在西南台地含量较高,Hg在西北部巴音乌拉山出现高值区域,其分布与变化受到天然因素和人类活动的双重影响;Cr^(6+)、As出现局部区域超标,超标率分别为8.45%和2.82%;Cr^(6+)主要超标区域在盐湖西南侧呈条块状分布,并在盐湖附近Cr^(6+)含量较高;As以点状超标,分布于西南部和东北部;盐湖盆地地下水87.3%处于安全清洁状态,仅5.6%轻度污染出现在西南部,不存在中度和重度污染;通过饮用水途径的化学致癌物的健康风险值远高于非化学致癌物的健康风险值,西南部图格力高勒沟谷区域化学致癌物Cr^(6+)超过了US EPA最大可接受风险,但整个盐湖盆地Cr^(6+)的平均健康风险值低于US EPA最大可接受风险;As和Hg均低于US EPA最大可接受风险;盐湖盆地总致癌风险特征与Cr^(6+)基本一致,Cr^(6+)平均健康风险占总致癌风险贡献率的89%;Cr^(6+)超标原因包括盐湖盆地高锰酸盐指数偏高,促使Cr3+氧化成为Cr^(6+),As与Cr存在一定的同源关系.

Jilantai salt lake basin in the arid area of northwest China was selected as the typical study area. 71 groundwater samples were collected, and of which Cr6＋, As, Hg and main chemical constituents were tested. The figures based on the geological statistics interpolation were plotted to reveal the spatial distribution characteristics of Cr6＋, As and Hg in the groundwater. The conditions of pollution and health risk from Cr6＋, As, Hg were assessed by the standard index method, the Nemerow index method and US EPA model. Source analysis of Cr6＋, Hg, As was carried out by statistical test. The results showed that： Cr6＋, As, Hg generally existed in the basin groundwater. The content of Cr6＋ in upper reaches and north-eastern part of the salt lake were higher, and the content of As in the south-western platform was higher. Hg concentration appeared higher value in the northwest Mountain Bayinwula. All of these distributions and changes were affected by nature and human activities. The content of Cr6＋ and As appeared excessive in the local area, and the excessive ratios were 8.45% and 2.82% separately. The main excessive areas of Cr6＋ were strip-like along with Tugeligaole Valley in the south-western part. As was excessive as spotted state and distributed in the southwest and northeast part. There were no moderate and severe pollution in the study area, and the 87.3% groundwater was safe and clean. There was local mild pollution area in southwest part of the salt lake. The health risk of chemical carcinogens by the way of drinking water was much higher than that of non-chemical carcinogens. Although chemical carcinogens Cr6＋ in the southwest part exceeded the maximum acceptable risk of US EPA, the average health risk of whole basin from Cr6＋ was lower than that limit; the chemical carcinogen As and non-chemical carcinogen Hg were both lower than the acceptable value. The distribution of total carcinogenic risk was consistent with Cr6＋s’, and the contribution rate of Cr6＋ was 89% for the total carcinogenic risk. The high content of Cr6＋ might be due to the higher permanganate index, which made Cr3＋ oxidation to Cr6＋. As and Cr were homologous source.