LEAD BIOAVAILABILITY - DISSOLUTION KINETICS UNDER SIMULATED GASTRIC CONDITIONS

The lower bioavailability of lead from mining sites compared to urban environments is due partially to the relative solubility of Pb-bearing phases in the respective mineral assemblages and to kinetic limitations relative to the residence time of soil in the gastrointestinal (GI) tract. In this study, Pb dissolution kinetics for mine-waste-impacted soil and for pure anglesite were diffusion controlled. Dissolution rates over stomach residence time (2 h) were 0.49 and 0.07 [(mg of Pb/L of solution)/(mg of solid Pb)(h)] for PbSO4 and test soil, respectively, and were linearly dependent on HCl concentration, whereas particle size did not affect dissolution rates except at mean diameters of <2.4-mu-m. Lead solubility decreased in the order Pb(OAc)2 > PbSO4 > test soil. Dissolution of only 4% SIGMA-Pb from the test soil after 2 h demonstrates that kinetics of Pb-bearing minerals in mine-waste-impacted soils is an important factor controlling Pb solubility in the GI tract.