Prediction of heavy metals mobility and bioavailability in contaminated soil using sequential extraction and biosensors

Several chemical and biological methods have been developed in the last decade to evaluate heavy metals mobility and bioavailability in contaminated soils. In this study, two methods, Biomet sensors and chemical sequential extraction [potentially bioavailable assessment sequential extraction (PBASE) method], were used to predict heavy metals bioavailability in the surface and heavy metals mobility in the subsurface of smelter-contaminated soils, respectively. The heavy metals considered (arsenic, copper, iron, lead, and zinc) were those detected in a previous sampling campaign performed in the contaminated area. Biomet biosensor results indicated that 15-25% of Cu and Zn were bioavailable for plants and animals uptake in the soil surface, whereas higher values were obtained for As and Pb (>60%). In the soil subsurface, iron was identified as the less mobile element, followed by As and Pb, since they were mainly present in the nonsoluble fractions of PBASE method. In contrast, Cu and Zn showed similar distribution between the soluble and nonsoluble fractions. Therefore, PBASE and Biomet are useful and complementary methods which supply different information about heavy metals occurrence in contaminated soils: the first method indicates their potential mobility, whereas the second one shows their potential bioavailability for biota.