若尔盖湿地土壤及水体重金属分布特征及健康风险评价

Distribution characteristics of heavy metals in soil and water and health risk assessment of Zoige Wetland

若尔盖湿地属典型的高寒湿地生态系统,是我国青藏高原生态屏障的重要组成部分.青藏高原地区重金属监测多集中在青藏高原西南部,针对若尔盖湿地重金属分布特征、污染来源及潜在人体健康风险尚未完全清楚.于2022年7月采集湿地土壤(退化湿地和未退化湿地)及地表水水样,分别对4种重金属(Cr、As、Cd和Pd)进行分析,阐述其浓度分布特征,并进行人体健康风险评估.结果表明:Cr、As、Cd和Pd在未退化湿地和退化湿地的浓度(mgkg-1)分别为6.23~26.19、2.06~45.00、0.01~0.63和1.32~10.87,7.56~23.56、5.10~21.87、0.01~0.43和2.16~11.13.参照《土壤环境质量——农用地土壤污染风险管控标准》,Cr、Pd、Cd和As达标率为100%、88%、94.4%、80%;地表水中Cd未检出,Cr、As和Pd浓度(μg·L-1)分别为0.04~1.14、0.15~23.77和0.01~0.94,符合国家地表水质量Ⅰ类标准.参照美国环保署(USEPA)和国际辐射防护委员(ICRP)标准,若尔盖湿地土壤总非致癌风险指数(HI)均小于1;总致癌风险(TCR)范围为2.53×10^(-6)~1.20×10^(-4),均在可接受致癌健康风险水平10-6~10-4数量级范围内;地表水中总健康风险指数(R)为1.97×10^(-6)~2.01×10^(-4),人体最大可接受风险水平为5.0×10^(-5),其中,21.4%地表水样品超过健康风险水平.As是导致健康风险的主导因子.研究结果可补充若尔盖地区环境背景值的基础数据库,为该地污染防治及环境质量改善提供一定的数据支撑.

Zoige Wetland is a typical high-altitude wetland ecosystem and an important component of the ecological barrier in the Qinghai-Tibetan Plateau.In July 2022,soil samples(degraded wetland and undamaged wetland)and surface water samples were collected for analysis of four heavy metals.The concentration distribution characteristics of chromium,arsenic,cadmium,and palladium in samples before and after wetland damage were described,and human health risk assessments were conduc-ted.The result showed that the concentrations of Cr,As,Cd,and Pd in undamaged and damaged wetlands were(mgkg-1):6.23-26.19,2.06-45.00,0.01-0.63,and 1.32-10.87,respectively.According to the Soil Environmental Quality-Agri-cultural Land Soil Pollution Risk Control Standard,the compliance rates for chromium,palladium,cadmium,and arsenic are 100%,88%,94.4%,and 80%,respectively.Overall,these research results indicated that the distribution characteristics of chromium,arsenic,cadmium,and palladium concentrations in soil varied before and after wetland damage,and most of them met relevant standards.However,attention still needs to be paid to the risk control level of palladium elements.In surface water,cad-mium was not detected,while the concentrations of Cr,As,and Pd were(μgL-1):0.04-1.14,0.15-23.77,and 0.01-0.94,respectively,all meeting the national surface water quality standard level I.Referring to the standards of the Environmental Protection Agency(USEPA)and the International Council on Radiation Protection(ICRP),the total non-carcinogenic risk in-dex(HI)of soil in Zoige Wetland was less than 1;the total carcinogenic risk(TCR)ranged from 2.53×10^(-6) to 1.20×10^(-4),all within the acceptable carcinogenic health risk level of 10-6 to 10-4.In surface water,the total health risk index(R)was from 1.97×10^(-6) to 2.01×10^(-4);the maximum permissible risk level for human consumption was 5.0×10^(-5).Among them,the proportion of samples exceeding the health risk level was 21.4%.This study found that the distribution of heavy metals in soil and water in Zoige Wetland had certain characteristics,with arsenic being the main factor leading to health risks.This study pro-vided certain data support for pollution prevention and control and environmental quality improvement in the Zoige area.