The influence of aging and compost amendment on bioaccessibility, bioavailability and toxicity of phenanthrene in contaminated soils

The risk related to the presence of hydrophobic contaminants in soil is mainly due to their availability, influenced by aging processes and the amount and quality of organic matter An improper estimation of the risk of a pollutant in soil. could affect whatever remediation action Therefore, integrated approaches are needed for a realistic evaluation of the contaminant availability. This work aims to correlate chemical extraction methods and bioassays to assess the bioaccessibility, bioavailability and toxicity of phenanthrene (PHE). Bioaccessibility and bioavailability of PHE in an agricultural soil polluted with 15 and 150 mg kg(-1) of PHE have been studied in relation to aging. effects (up to 240 days) and compost amendments (10 and 30 t ha(-1)). The bioaccessibility, evaluated by means of the PHE amount desorbed by Tenax TA resin, evidenced a decrease in PHE amount extracted at 240 days, with respect to that extracted at 20 days (aging effect) in the presence of 15 mg kg PHE, and at 10 t ha(-1) of compost addition. The addition of higher doses of compost (30 t ha(-1)) evidenced a reduction of the bioaccessible PHE fraction after only 20 days of aging. No differences were observed in samples contaminated with 150 mg kg(-1) of PHE. The bioavailability was assessed by PHE uptake in Eisenia andret (Annelida. Lumbricidae) exposed for 14 days to soil samples This parameter showed a marked reduction with ailing and compost amendment both at 15 and 150 mg kg(-1) of PHE concentration. A reduction of the acute toxicity (mortality of individual earthworms) and of morphological alterations in immune system cells were observed after 240 days of aging in all samples. Results evidenced that the toxicity of PHE was well correlated with the bioavailability. However, the relationships between the bioaccessibility and the two above-mentioned parameters were less clear.