A Study of the In Vitro Bioaccessibilities of Nickel Compounds in Particulate Form as they are Affected by Variation in Assay Conditions
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Abstract
In vitro bioaccessibility of Ni from NiO, NiSO4, Ni3S2, NiS, and Ni metal in the absence of soil was measured under assay conditions known to influence the percent of total metal leached. Dissolution of Ni increased with extraction ratio (mL of extractant : g of total Ni) and incubation time for all compounds except NiO. Patterns of ER regulated dissolution included an increasing relationship (NiSO4), a threshold relationship (NiS, Ni3S2, Ni metal), and for NiO, a decreasing relationship. Dissolution of the compounds as a function of particle specific surface area suggested that metal removal from the dissolving surface was limited for NiO. Ni in NiO was the least bioaccessible of the compounds and bioaccessibility was negatively correlated with increased extraction ratio, likely a surface-access limitation that developed during dissolution at lower extraction ratios. As NiO is a main form in Ni in smelter-contaminated soils, these data suggest that their risk assessment could be complex.