Interaction effects of As, Cd and Pb on their respective bioaccessibility with time in co-contaminated soils assessed by the Unified BARGE Method.

Abstract

Interaction effects of As, Cd and Pb on their respective bioaccessibility in co-contaminated soils were reported. In addition, the influence of aging time (up to 90days) on potential interactions was also investigated. Experiments were carried out by spiking four diverse soils with single, binary or ternary mixtures of As, Cd and Pb. Soils were measured for bioaccessibility at different aging periods. Results demonstrate that bioaccessibility of As, Cd and Pb reached a steady state after soils were aged for 30days. Bioaccessibility of As, Cd and Pb in soils spiked with binary mixtures of As, Cd and Pb were not affected by the other co-existing metal/metalloid. But when As, Cd and Pb were introduced together to acidic soils which lacked abundant binding sites, intestinal bioaccessibility of Cd was increased at the early stage of aging (7 to 30days) whilst bioaccessibility of As and Pb remained unchanged. However, when Pb and As were added after Cd has been incubated in soil for 7days, Cd intestinal bioaccessibility was not influenced by As and Pb. Therefore, a number of factors should be taken into consideration when estimating the bioaccessibility of mixed As, Cd and Pb, including the loadings of As, Cd and Pb in soils, the time for which they have been aged together and the time period between As, Cd and Pb entering the soils.