A Study On The Bioaccessibility Of Lead In Two Types Of Soil And The Health Risk Assessment

In order to promote the implementation of solving heavy metal in pollution soil, conducting health risk assessment of contaminated soil has become a necessary mean of the reusing land. Traditional health risk assessment system excessively focused on protecting human health, resulting in excessive restoration in contaminated sites. Therefore, bioavailability was recommended to complete health risk assessment system. At present, different in vitro methods have differences in design principle and initial purpose, which lacks uniform standard. This not only caused the lack of comparability between different in-vitro results, but also caused the arbitrariness of selection and use of in vitro digestion method.To complete the unification and normalization of in vitro digestion method, five kinds of in vitro test method:PBET (Physiologically Based Extraction Test) SBET (Simple Bioaccessibility Extraction Test), IVG (In Vitro Gastrointestinal), RIVM (The National Institute for Public Health and the Environment) and DIN (German institute for standardization), were chosen in this study. Two tested soils have significantly differences in soil properties. Research mainly includes the comparison of acidic and alkaline soil lead bioavailability, in vitro methods screening, the extraction of digestive enzyme function and biochar remediation assessment based on bioavailability. Main conclusions are the following three points:(1) The suitable in-vitros for acid and alkaline soils Pb was PBET. The Pb bioavailabilities in acid and alkaline soil were 13.5%-38.5%,5.4% 17.1%respectively, and had a well correlation with animals. And from a security view, soil screening values:142.9 mg·kg-1 and 320.9 mg·kg-1 based on PBET, were relatively consistent with GB 15618-2008 on residential land standard and risk control trends.(2) Three in-vitros:PBET, IVG, SBET, were chosen in this study. The soil lead bioavailability in each method was respectively evaluated with and without digestive enzymes and the differences were compared. The results showed that the difference of digestive enzymes extracting ability was found in different types of soil; the extracting ability of digestive enzyme on Pb bioavailability was significant in alkaline soil, whereas no significant difference was found in acidic soil.Pepsin, pig bile salts and pancreatic enzyme had significant effect on lead extraction in both soils.(3) Three in-vitros:PBET, IVG, SBET, were chosen to assess biochar remediation effect. The results showed that:① From the perspective of the health risk assessment, the addition amount of biochar might be between 2% and 4% in non-agricultural contaminated soil. However, it is not a feasible solution for high lead concentrations condition. ②Different in-vitros impacted on assessment of biochar remediation effect. Therefore, choosing the appropriate in-vitros is very crucial.