摘要:
为获取土壤细颗粒组分中污染物的浓度及其生物可给性，分析了某铬渣污染场地土壤PM10和PM2.5组分中六价铬的浓度分布特征，并采用统一生物可给性测试方法(Unified Bioaccessibility Method,UBM)和呼吸吸入生物可给性测试方法(Inhalation Bioaccessibility Method,IBM)2种体外模拟法测试了六价铬在胃、肠及肺中的生物可给性。结果显示：(1)六价铬和总铬在PM10和PM2.5组分中的含量大多明显低于PM250组分，PM10组分中六价铬和总铬的累积因子(accumulation factors,AF)分别为0.080~12.297和0.008~0.261，PM2.5组分中六价铬和总铬的AF分别为0.019~5.721和0.005~0.342，相比于总铬而言，六价铬在细颗粒中的累积程度更高。较低的有机质(organic matter,OM)含量可能导致了六价铬AF的明显增加。不同组分中六价铬占总铬的比例分别为2%~17%(<250 μm)、21%~98%(<10 μm)和22%~82%(<2.5 μm)，表明在土壤细颗粒中，铬更多地以六价铬的形式存在；(2)通过UBM获取的PM250组分中六价铬在胃提取阶段的生物可给性因子为0.0301%~0.9483%，平均值为0.4821%；肠阶段可给性因子为0.0018%~0.3934%，平均值为0.1578%，约为胃提取阶段的0.33倍；(3)通过IBM获取的PM10组分中六价铬在肺阶段的生物可给性因子为2.52%~41.50%，平均值14.47%；PM2.5组分中六价铬的生物可给性因子为2.40%~88.12%，平均值为48.86%，约为PM10组分的3.38倍；(4)在考虑生物可给性条件下，六价铬产生的人体总致癌风险水平从2 430.04×10-6下降至125.83×10-6，而且，六价铬呼吸途径产生的致癌风险水平极高，是经口摄入的5.04~176.38倍(胃)、10.92~10 198.00倍(肠)，表明呼吸吸入是六价铬致癌风险最为关键的暴露途径。因此，通过测定土壤细颗粒组分中六价铬的生物可给性，能够显著提高铬渣污染土壤健康风险评估的可靠性。
Abstract:
In order to obtain the concentration of contaminants in the fine particles and their bioaccessibility in humans, the concentration distribution characteristics of hexavalent chromium in PM10 and PM2.5 fractions of chromium ore processing residue-contaminated site was analyzed. The Unified Bioaccessibility Method (UBM) and Inhalation Bioaccessibility Method (IBM) were adopted to measure the bioaccessibility of hexavalent chromium in the stomach, intestine and lung. The results revealed that: (1) The content of hexavalent chromium and total chromium in PM10 and PM2.5 fractions were mostly lower than that of PM250 fraction. The accumulation factors (AF) of hexavalent chromium and total chromium in PM10 fraction were 0.080～12.297 and 0.008～0.261, respectively. And the AF of hexavalent chromium and total chromium in PM2.5 fraction were 0.019～5.721 and 0.005～0.342, respectively. Compared to total chromium, there were more hexavalent chromium accumulated in fine particles. The lower organic matter (OM) content might lead to a significant increase in the AF of hexavalent chromium. The percentage of hexavalent chromium to total chromium in different fractions were 2%～17% (<250 μm), 21%～98% (<10 μm), and 22%～82% (<2.5 μm), respectively. It appeared that in the finer granularity of soil particles, hexavalent chromium account for a higher proportion; (2) The bioaccessibility in the stomach stage of hexavalent chromium in the PM250 fraction measured by UBM was 0.0301%～0.9483%, with an average of 0.4821%. The bioaccessibility of hexavalent chromium in the intestine stage was 0.0018%～0.3934%, with an average of 0.1578%, which was about 0.33 times lower than that of the stomach extraction stage; (3) The bioaccessibility in the lung stage of hexavalent chromium in the PM10 fraction measured by IBM was 2.52%～41.50%, with an average of 14.47%. The bioaccessibility of hexavalent chromium in the PM2.5 fraction was 2.40%～88.12%, with an average of 48.86%, which was about 3.38 times higher than that of the PM10 component; (4) The total carcinogenic risk level of hexavalent chromium decreased from 2 430.04×10-6 to 125.83×10-6 under consideration of the bioaccessibility. In addition, the carcinogenic risk level of hexavalent chromium in the respiratory pathway was 5.04～176.38 times higher than that of stomach and 10.92～10 198.00 times higher than that of intestine in case of oral intake, respectively. It is indicated that respiratory was the most critical exposure route for hexavalent chromium carcinogenic risk. To conclude, the reliability of the health risk assessment was improved significantly, with the determination of the bioaccessibility for hexavalent chromium in the fine particle fraction of soils.
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