Keywords: 
• antimony /
• Folsomia candida /
• toxic effect /
• aging /
• speciation

Abstract: Metal aging in soils has been regarded as an important factor influencing its availability and toxicity to organisms. To understand the effect of aging on the speciation and toxicity of antimony (Sb) in soil, combining with chemical analysis and bioassay, we reported the changes of the oxidative state, water soluble fraction of exogenous Sb(Ⅲ) and its acute/chronic toxicity to Folsomia candida after 7 d and 60 d aging in moisture soil of Beijing. The results indicated that Sb(Ⅴ) was predominant in soil with low Sb concentrations when just being aged for 7 d, whereas only 47.4%, 27.5% and 2.2% of Sb(Ⅲ) were transformed into Sb(Ⅴ) when concentrations reached 1 600, 2 400, 4 800 mg·kg^-1, but the percentage of Sb(Ⅴ) increased to 38.1% in soil with the highest concentration of 4 800 mg·kg^-1 and the Sb(Ⅴ) predominated in the other treatments when being aged for 60 d. The water soluble Sb in soil decreased significantly during the aging. Consistent with the changes of water soluble Sb and oxidation of high toxic Sb(Ⅲ) to low toxic Sb(Ⅴ), the toxicity of Sb to Folsomia candida reduced greatly as aging time prolonged. When the soil being aged for 7 d, the LC₅₀ value of acute survival was 2 105 mg·kg^-1, the LC₅₀ of chronic survival was 683 mg·kg^-1, and the EC₅₀ values of reproduction was 307 mg·kg^-1; when the soil being aged for 60 d, the mortality did not reach 50% in acute and chronic survival test, and the EC₅₀ of reproduction was 1 419 mg·kg^-1.Therefore, in order to avoid overestimating the ecological risk of Sb with varying oxidative state, it is especially important to consider the effect of aging.