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Effects of Chemical Speciation on the Bioaccessibility of Zinc in Spiked and Smelter-Affected Soils

机译：化学形态对尖峰和冶炼厂土壤中锌生物有效性的影响

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Previous studies have suggested that understanding soil metal speciation, rather than relying solely on total metal content, can improve the accuracy and utility of contaminated site risk assessments. Because soil properties and reaction time can alter metal speciation, speciation should influence metal bioaccessibility. For example, under gastrointestinal conditions, it is expected that metal species will differ in bioaccessibility depending on their stability in acidic pH environments. We studied the links between metal speciation and bioaccessibility. A combination of synchrotron-based X-ray diffraction and X-ray absorption near edge structure (XANES) was used to identify the zinc (Zn) speciation in spiked and smelter-affected soils. After conducting in vitro digestion tests on the soil samples, XANES and linear combination fitting were carried out on the residual pellets to identify the species of Zn that remained after digesting the soils in the simulated gastric and duodenal fluids. The metal species that were not present in the residual pellets were inferred to have been dissolved and, thus, more bioaccessible. Sphalerite (ZnS), ZnO, and outer-sphere Zn contributed more to Zn bioaccessibility than franklinite (ZnFe2O4) and Zn incorporated into a hydroxy interlayer mineral (Zn-HIM). The bioaccessibility of Zn-aluminum layered double hydroxides (Zn-Al-LDH) was found to be inversely proportional to its residence time in soil. It was also observed that the relatively high pH of the duodenum favors metal reprecipitation and readsorption, leading to a reduction in bioaccessible metal concentration. These results imply that metal speciation mainly controls metal bioaccessibility. Environ Toxicol Chem 2019;38:448-459. (c) 2018 SETAC.
机译：先前的研究表明，了解土壤金属形态而不是仅依赖于总金属含量，可以提高污染场地风险评估的准确性和实用性。由于土壤性质和反应时间会改变金属的形态，因此形态会影响金属的生物可及性。例如，在胃肠道条件下，预计金属种类的生物可及性将取决于它们在酸性pH环境中的稳定性。我们研究了金属形态与生物可及性之间的联系。基于同步加速器的X射线衍射和近边缘结构X射线吸收（XANES）的组合用于鉴定加标和冶炼厂影响的土壤中的锌（Zn）形态。在对土壤样品进行体外消化测试后，对残留的颗粒进行XANES和线性组合拟合，以鉴定在模拟的胃和十二指肠液中消化土壤后残留的锌的种类。推断残留颗粒中不存在的金属物质已经溶解，因此更易于生物利用。闪锌矿（ZnS），ZnO和外球面Zn的分布比富兰克林石（ZnFe2O4）和掺入羟基夹层矿物（Zn-HIM）中的Zn对Zn生物可及性的贡献更大。锌铝层状双氢氧化物（Zn-Al-LDH）的生物可及性与其在土壤中的停留时间成反比。还观察到十二指肠的相对较高的pH有利于金属的再沉淀和再吸收，从而导致生物可利用的金属浓度降低。这些结果暗示金属形态主要控制金属的生物可及性。 Environ Toxicol Chem 2019; 38：448-459。 （c）2018年SETAC。

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