[Mild solvent extraction technique for the evaluation of PAHs bioavailability]

Area of Science:

• Environmental Chemistry
• Soil Science
• Ecotoxicology

Background:

• Aged agricultural soils can contain significant levels of polycyclic aromatic hydrocarbons (PAHs).
• Understanding PAH bioavailability is crucial for assessing ecological risks.
• Earthworms (Eisenia fetida) are important soil organisms for evaluating contaminant uptake.

Purpose of the Study:

• To extract and quantify PAHs in aged agricultural soils using n-butanol and hydroxypropyl-beta-cyclodextrin (HPCD).
• To assess the bioavailability of different molecular weight PAHs to earthworms.
• To evaluate the efficacy of mild solvent extraction as a predictor of PAH bioavailability.

Main Methods:

• Soil samples were collected from nine aged agricultural fields.
• PAHs were extracted using n-butanol and hydroxypropyl-beta-cyclodextrin (HPCD).
• Bioavailability was assessed by measuring PAH accumulation in Eisenia fetida.

Main Results:

• High molecular weight PAHs (≥ 4 rings) constituted the largest proportion of soil contaminants (4-ring: 34.06%, 5-6 rings: 34.09%).
• Light molecular weight PAHs were readily accumulated by earthworms, while high molecular weight PAHs showed low accumulation.
• Mild solvent extraction showed a good correlation with 3-ring PAHs (r² 0.77-0.79) but not with other PAH ring sizes (r² <0.35).

Conclusions:

• High molecular weight PAHs are persistent contaminants in aged agricultural soils.
• Earthworm bioaccumulation is inversely related to PAH molecular weight.
• Mild solvent extraction is not a suitable predictor for the bioavailability of most PAHs to earthworms in these soils.