Earth Sciences Graduate Program, Institute of Geology, National University of Mexico, Colosio y Madrid, Hermosillo, Sonora 83240, Mexico.
Department of Geology, University of Sonora, Rosales y Encinas, Hermosillo, Sonora 83000, Mexico; National Laboratory of Geochemistry and Mineralogy - LANGEM, Mexico.
Sci Total Environ. 2019 Mar 20;657:1468-1479. doi: 10.1016/j.scitotenv.2018.12.148. Epub 2018 Dec 11.
Understanding the oral bioaccessibility of lead (Pb) present in soils in urbanized areas is important for the human exposure risk assessment. In particular, the role of the soil-mineralogy in the oral bioaccessibility has not been extensively studied. To investigate bioaccessibility, five types of periurban soils were collected, samples were spiked with the same amount of lead-chromates from traffic paint, and subjected to the in vitro Physiological Based Extraction Test (PBET). Ten samples of urban topsoils were collected at elementary schools playgrounds, Pb-bioaccessibility was measured, and a prediction equation for bioaccessibility was constructed. Mineralogy, and metal content were identified with a combination of X-ray powder diffraction, scanning electron microscopy, and portable X-ray fluorescence techniques. Traffic paint sample is made of 15% quartz (SiO), 13% crocoite (PbCrO), 55% calcite (CaCO), and 17% kaolinite (AlSiO(OH)) and it contains high metal content (Pb, Cr, Zn, and Ca). Studied soils are characterized by variable amounts of acid-neutralizing minerals (carbonates) and low metal content. Spiked soils contained almost equal concentration of Pb, Cr, and Zn, because the contribution of these metals is from the added paint. However, obtained Pb-bioaccessibility at gastric and intestinal conditions are variable (40 to 51% gastric, 24 to 70.5% intestinal). Carbonate content shows significant correlation (p < 0.05) with Cr, Ca, calcite, crocoite, and Pb-bioaccessible at gastric conditions. Correlation of Pb-bioaccessible at intestinal conditions is significant (p < 0.05) with kaolinite. Variability of Pb-bioaccesibility in urban environments is commonly associated to differences in Pb-sources, however, our results show that the bioaccessibility of the same pollutant behaves different for each soil type. This suggests that soil mineralogy may play a role in Pb-releasing at gastrointestinal conditions. Soil information about mineralogical characteristics from this study may help to reduce exposure to lead from urban sources if data are incorporated into urban planning.
了解城市化地区土壤中铅 (Pb) 的口腔生物可给性对于人体暴露风险评估很重要。特别是，土壤矿物学在口腔生物可给性中的作用尚未得到广泛研究。为了研究生物可给性，采集了 5 种城郊土壤，向土壤中添加相同数量的来自交通漆的铬酸铅，并进行体外生理基础提取测试（PBET）。在小学操场采集了 10 个城市表层土壤样本，测量了 Pb 的生物可给性，并构建了生物可给性的预测方程。利用 X 射线粉末衍射、扫描电子显微镜和便携式 X 射线荧光技术组合确定了矿物学和金属含量。交通漆样本由 15%石英 (SiO)、13%铬铅矿 (PbCrO)、55%方解石 (CaCO) 和 17%高岭石 (AlSiO(OH)) 组成，且含有高金属含量（Pb、Cr、Zn 和 Ca）。研究土壤的特点是具有不同数量的酸碱中和矿物（碳酸盐）和低金属含量。添加的土壤含有几乎相等浓度的 Pb、Cr 和 Zn，因为这些金属的贡献来自添加的油漆。然而，在胃和肠道条件下获得的 Pb 生物可给性是可变的（40%到 51%的胃，24%到 70.5%的肠）。碳酸盐含量与 Cr、Ca、方解石、铬铅矿和胃条件下的 Pb 生物可给性呈显著相关（p<0.05）。肠道条件下的 Pb 生物可给性与高岭石呈显著相关（p<0.05）。城市环境中 Pb 生物可给性的可变性通常与 Pb 源的差异有关，然而，我们的结果表明，相同污染物的生物可给性因土壤类型而异。这表明土壤矿物学可能在胃肠道条件下释放 Pb 方面发挥作用。如果将这些数据纳入城市规划，本研究中关于土壤矿物学特征的土壤信息可能有助于减少城市来源的铅暴露。
