Bioaccessibility of Metals in Soils at Typical Legacy Industrial Sites: In Vitro Evaluation Using Physiologically-Based Extraction

Risk assessment of soil metal pollution based on total metal contents might give overestimates by neglecting the bioaccessibility of the pollutants to soil biota. Physiologically-based extraction tests (PBET) are in vitro methods for evaluation of bioaccessibility of soil pollutants. A total of 27 soil samples collected from four types of legacy industrial site representing metal smelting, lead-acid battery factories, chemical plants and steel plants were analyzed for the bioaccessibility of six potentially toxic metals using a PBET method. The metal pollutants at the industrial sites depended on the former industrial processes and emissions. The highest proportions of gastric phase and intestinal phase in these soil samples were 43.9% for Cd and 27% for Cu, respectively. Factors affecting metal bioaccessibility included type of industry and soil properties. The soils at a lead-acid battery factory showed relatively high bioaccessibility of Pb, Zn and Cd and those at the steel plant showed relatively low metal bioaccessibility. Soil organic matter and clay contents were positively related to metal bioaccessibility but soil pH and CEC showed negative relationships. Further studies are recommended to determine the speciation of the bioaccessible metals in these soils.