老化土壤中As的人体可给性控制因素及健康风险

采用UBM(unified bioaccessibility model)模拟胃肠消化的方法测试了来自湖南省、广西壮族自治区和大连市的13个不同理化参数污染土壤中As的人体可给性,分析了考虑As人体可给性对风险评估结果的影响. 结果表明:①供试土壤样品模拟胃提取阶段As的人体可给性因子为3.9%~49.5%,平均值为19.6%；模拟肠提取阶段的人体可给性因子为1.2%~10.8%,平均值为6.0%,前者是后者的1.2~9.1倍. ②影响供试土壤样品胃提取阶段As人体可给性浓度的最显著性因素是w(TAs)(R2=0.94,P<0.01,n=13),其次为w(TP)(R2=0.82,P<0.01,n=13)和w(TMn)(R2=0.79,P<0.01,n=13)；影响肠提取阶段As人体可给性浓度的显著因素依次为土壤w(TAs)(R2=0.83,P<0.01,n=13)、w(TP)(R2=0.80,P<0.01,n=13)、胃提取阶段As的人体可给性浓度(R2=0.76,P<0.01,n=13)、pH(R2=0.74,P<0.01,n=13)、w(TMn)(R2=0.65,P<0.02,n=13)以及w(TOM)(TOM为有机质)(R2=0.59,P<0.04,n=13). ③基于土壤w(TAs)和w(黏粒)构建的模型能较好地预测As在胃提取阶段的人体可给性浓度,预测值与实测值的R2达到0.97,ME(平均误差)、RMSE(均方根误差)、r_p2(可决系数)分别为0.02、0.17、0.95；仅基于土壤w(TAs)构建的模型能较好地预测As在肠提取阶段的人体可给性浓度,R2达到0.90,ME、RMSE、r_p2分别为-0.03、0.26、0.80. ④以供试土壤样品中w(TAs)为暴露浓度计算的健康风险分别是考虑As在胃及肠提取阶段人体可给性因子的2.0~15.0和7.3~81.0倍. 可见,基于土壤w(TAs)所制定的风险管理对策可能过于保守. 

Factors Controlling Arsenic Bioaccessibility in Aged Soils and Corresponding Health Risks

The unified bioaccessibility model (UBM) was used to measure Arsenic (As) bioaccessibility of 13 soils with different physio-chemical properties and concentrations from Hunan, Guangxi and Dalian. Furthermore, the implications of incorporating As bioaccessibility into risk assessment were evaluated. The results revealed that the bioaccessibility of As in the stomach was between 3.9%-49.5%, with the arithmetic mean being 19.6%, while in the intestine it was 1.2%-10.8%, with the arithmetic mean being 6.0%. The bioaccessibility in the stomach was 1.2-9.1 times that in the intestine. The most significant factor controlling the bioaccessibility of As in the stomach was w(TAs) in soil (R2=0.94, P<0.01, n=13), followed by w(TP) (R2=0.82, P<0.01, n=13) and w(TMn) (R2=0.79, P<0.01, n=13). In the intestine, the most significant factor was also w(TAs) (R2=0.83, P<0.01, n=13), followed by w(TP) (R2=0.80, P<0.01, n=13), As bioaccessible concentration in the stomach (R2=0.76, P<0.01, n=13), pH (R2=0.74, P<0.01, n=13), w(TMn) (R2=0.65, P<0.02, n=13) and w(TOM) (R2=0.59, P<0.04, n=13). A regression model based on w(TAs) and w(clay) in soil was tested, and able to predict As bioaccessibility in the stomach with R2, ME, RMSE and r_p2 being 0.97,0.02,0.17 and 0.95, respectively. For As bioaccessibility in the intestine, a model constructed based only on w(TAs) could be used to predict its bioaccessibility precisely, with R2, ME, RMSE and r_p2 being 0.90,-0.03, 0.26 and 0.80, respectively. The health risk calculated based on w(TAs) was 2.0-15.0 times and 7.3-81.0 times the values when bioaccessibility in the stomach and intestine was incorporated, indicating the conservative nature of the current assessment approach assuming the bioaccessibility of contaminants in soil to be 100%.