Abstract
Current researches found some terrestrial animals absorb petroleum hydrocarbons (PHCs) in oil-polluted soil. However, the absorption behaviour between various biological tissues remains unclear. The aim of our study is to determine the toxic effects and enrichment behaviours of earthworms (Eisenia fetida) in petroleum-contaminated soils and to provide a reasonable dynamics model to explain the migration of PHCs within earthworm tissues. The PHCs are divided into three fractions by equivalent carbon number. An experimental analysis of the PHC concentrations in 3 different earthworm organ systems (body-wall tissue, body fluid and gut tissue) from a contamination exposure experiment at different time intervals was implemented. A dynamics model was built to simulate the absorption mechanism. The model results perform well. The PHC concentrations in the earthworm tissues were gut > body fluid > body wall. The PHCs in the gut reached equilibrium first, and those in the body-wall tissues reached equilibrium last. In the gut tissue, the PHC concentration was different from those in the body-wall tissue and body fluid due to the influence of the feeding rule. In addition, as the length of the carbon chain increases, the molecular size increases, which makes it more difficult for petroleum hydrocarbon fractions to enter an organ system. As a result, the concentration of PHCs in each type of tissue decreases with increasing carbon chain length. This study can provide a theoretical foundation for chemical monitoring in soil.
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