Accurate prediction bioaccessibility of PAHs in soil-earthworm system by novel magnetic solid phase extraction...

Conventional chemical extraction methods may lead to overestimate or underestimate bioaccessibility due to their inability to provide realistic kinetic information regarding PAHs in soils. In this study, we propose the use of magnetic solid phase extraction (MSPE) technique for assessing the bioaccessibility of PAHs in the soil-earthworm system. Firstly, a novel polydopamine-coated magnetic core-shell microspheres (Fe₃O₄-C_16@PDA) was developed by a one-pot sol-gel and self-polymerization method. The PDA coatings not only enhance the hydrophilicity of material surfaces but also exhibit excellent biocompatibility. The maximum adsorption capacity of Fe₃O₄-C_16@PDA for 16 PAHs was 52.72 mg g^-1, indicating that the proposed material fulfills the assessment requirements for highly contaminated soil. To compare the measurement of PAHs and their uptake by earthworms (Eisenia fetida), experiments were conducted using four different soils with varying properties. The desorption kinetics data obtained from these experiments demonstrated that the capability of the MSPE in accurately predicting the bioavailable portions of PAHs. After a 28-day exposure, the best predictor of bioavailable PAHs in earthworms was MSPE method exhibited the highest correlation coefficient (R² > 0.90), and its slopes in the four soils were 0.972, 0.961, 1.012, and 0.962, respectively, all close to 1. These results demonstrate that the MSPE method successfully mimics the conditions encountered in soil-earthworm systems and effectively assess bioaccessibility of PAHs in soils.