Abstract: As a new kind of persistent organic pollutants, perfluorooctane sulfonate (PFOS) has become a research spot of environmental science and toxicology. Its impacts on ecological environment should be deeply studied. In this paper, standard contact filter paper test of OECD, artificial soil test, and natural soil test were adopted to study the effects of PFOS on the acute lethality and avoidance behavior of earthworm. The results showed that the acute toxicity of PFOS on earthworm was related to the toxicant exposure time and concentration. The LC₅₀,48 h in filter paper test, LC₅₀,14 d in artificial soil test, andLC₅₀,14 d in natural soil test were 13.64 μg·cm^-2, 955.28 mg·kg^-1, and 542.08 mg·kg^-1, respectively. At the maximum test concentration of 160
 mg·kg^-1, the earthworm in artificial soil and natural soil showed significant avoidance behavior, which proved that earthworm could perceive and avoid the soil contaminated by a higher concentration of PFOS. To assess PFOS-contaminated soils, the avoidance endpoint was more sensitive than the mortality endpoint. PFOS had higher acute toxicity on earthworm in natural soil than in artificial soil. Meanwhile, more significant avoidance reaction was observed in natural soil than in artificial soil at the same concentrations of PFOS.

Key words: perfluorooctane sulfonate (PFOS), earthworm, acute toxicity, avoidance behavior, heavy metal, bioavailability, mangrove sediment, Dongzhai Harbor.