西南某含氯碱工业园区土壤-地下水中钡的迁移及人体健康风险评估

Migration and Human Health Risk Assessment of Barium in Soil-groundwater of An Industrial Park Containing Chlor-alkali Sector in Southwest China

为探究某城市工业园区中氯碱企业钡在土壤-地下水的吸附特征与迁移规律及其对人体健康的风险,采用ArcGIS分析钡在工业园区土壤中的空间分布特征,探讨钡在土壤-地下水系统的吸附、迁移规律,并采用人体健康风险指数模型评估工业园区内土壤-地下水中钡的人体健康风险水平。结果表明,钡主要集中在氯碱企业区域,土壤中钡最高浓度达25000 mg·kg^(-1),平均浓度为1584 mg·kg^(-1),远超区域土壤背景值292.6 mg·kg^(-1)。土壤对钡的吸附符合线性等温吸附方程,吸附系数(K _(d))为0.0011,表明土壤对于钡的固持能力较弱。浸出试验中渗滤液钡的浓度随着时间的推移而降低,并在第4天稳定在40 mg·L^(-1),表明钡可以通过垂直迁移渗入地下水。Visual MODFLOW模型预测表明区域地下水下游及周边河流水体钡浓度最大值分别为147 mg·L^(-1)、13.9 mg·L^(-1),远超钡在我国《地下水质量标准》(GB/T 14848—2017)中的Ⅲ类筛选值0.7 mg·L^(-1)和《地表水环境质量标准》(GB 3838—2002)中的标准值0.7 mg·L^(-1)。人体健康风险评价发现区域土壤中钡对儿童的危害指数(HI)小于成人,分别为0.545、1.018,这与以往其他重金属的人体健康风险评估结论相反。成人的危害指数超过非致癌健康风险的接受范围(HI<1),表明研究区域内土壤中的钡对成人存在非致癌健康风险(NCR)。地下水下游10 m、200 m和毗河水系处钡对儿童和成人的HI分别为27.788、16.021、2.628和21.215、12.232、2.006,表明钡可在地下水中扩散,并对人体健康产生威胁。综上,氯碱企业生产过程中钡母液的渗漏可引起区域土壤-地下水钡污染,同时威胁附近居民健康。

This study used ArcGIS to visualize the spatial distribution of barium in soil,and analyzed the adsorption and migration characteristics of barium in soil-groundwater system.Furthermore,the human health risk index was applied to evaluate the human health risk of barium in soil-groundwater.The results showed that barium was mainly accumulated in the area of chlor-alkali enterprises,with a maximum concentration of 25000 mg kg^(-1) and an average concentration of 1584 mg·kg-1,far higher than the regional background value of 292.6 mg·kg^(-1).The adsorption of the soil for barium could be described by linear isothermal adsorption equation and K_(d) was 0.0011,indicating that the absorption capacity of soil for barium was weak.Leaching test showed that the concentration of barium in the leachate reduced with time and stabilized at 40 mg·L^(-1)on the fourth day.Due to the high content of barium in the leachate,the leachate could be hazardous to the groundwater system.Visual MODFLOW model showed that the maximum anticipated barium concentrations in the nearby and downstream rivers were 147 mg L^(-1) and 13.9 mg L^(-1),respectively,far exceeding the ClassⅢscreening value(0.7 mg·L^(-1))in Standard for Groundwater Quality(GB/T 14848—2017)and the standard value(0.7 mg·L^(-1))in Environmental Quality Standards for Surface Water(GB 3838—2002).The human health risk index of barium in soil-groundwater was assessed according to the human health risk assessment model.It was found that the hazard index(HI)of barium in the soil to children was lower than that of adults,with 0.545 and 1.018,respectively,which was contrary to previous human health risk assessment conclusions for other heavy metals.The hazard index of adults exceeded the acceptable range of non-carcinogenic health risks(HI<1),indicating that there is a non-carcinogenic risk(NCR)for adults from the barium.At 10 m,200 m downstream of groundwater,and in the Pi River system,the HI values of barium for children were 27.788,16.021,and 2.628,while the values for adults were 21.215,12.232,and 2.006,respectively.This showed that barium caused some harm to humans after diffusing into underground water.In conclusion,barium pollution in soil-groundwater is detrimental to human health,which may result from the leaching of barium-containing liquid in the chlor-alkali business.