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. Since soil properties and reaction time can alter metal speciation, then speciation should influence metal bioaccessibility. For example, under gastrointestinal conditions, it is expected that metal species will differ in bioaccessibility depending upon their stability in acidic pH environments. We studied the links between metal speciation and bioaccessibility. A combination of synchrotron‐based X‐ray diffraction (XRD), X‐ray absorption near edge structure (XANES) were used to identify the Zn speciation in spiked and smelter‐affected soils. After conducting in vitro digestion tests on the soil samples, XANES and linear combination fitting (LCF) 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 are 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‐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. This article is protected by copyright. All rights reserved

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reprecipitation example absorption near edge structure synchrotronbased xray diffraction xrd digestion spiked and smelteraffected soils hydroxy interlayer mineral contaminated site risk linear combination fitting metal bioaccessibility znal ldh reaction residence

Essouassi Elikem, Brian D. Laird, Jordan Hamilton, Katherine Stewart, Steven D. Siciliano, Derek Peak,.Effects of Chemical Speciation on the Bioaccessibility of Zinc in Spiked and Smelter‐Affected Soils. 0 (0),.

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Essouassi Elikem, Brian D. Laird, Jordan Hamilton, Katherine Stewart, Steven D. Siciliano, Derek Peak,"Effects of Chemical Speciation on the Bioaccessibility of Zinc in Spiked and Smelter‐Affected Soils"