| Roxarsone, an animal feed additive, was widely used in poultry production. It was excreted unchanged in the manure and introduced into environment when animal litter was applied to farmland as fertilizer, which would pollute soils and water.A high performance liquid chromatography (HPLC) method was developed for determination of roxarsone levels in soils. The degradation of roxarsone in soil and the influences of some environmental factors as soil microorganisms, temperature, soil moisture and light were researched in laboratory. The exponential model was imitated the dynamic degradation of roxarsone in soils.The soil samples were extracted by 0.05 mol/L dipotassium hydrogen phosphate for HPLC analysis. The mobile phase was 0.05 mol/L potassium dihydrogen phosphate- methanol-10% acetic acid 85︰5︰10. A ODS-2 C18 column (150×4.6mm, 5.0μm), and ultraviolet detecter (264nm) was used . The mean recoveries of roxarsone ranged from 81.95%～88.21% at the added doses of 0.4, 4 and 20mg/kg of roxarsone, with the average intra-batch and inter-batch precisions 1.24%～2.96%. The linear calibration curves were obtained over the concentrations ranging from 0.1～100.00mg/L and coefficients was more than 0.999. The limit of detection (LOD) and limit of quantitation (LOQ) of roxarsone in soils was established at 0.1mgkg and 0.2mg/kg respectively. The HPLC method can be preferably used for residue measure of roxarsone in soils .Effects of various environmental factors such as microorganisms, soil moisture, temperature and light shining on the roxarsone degradation in soils were investigated. Results showed that the degradation rate of roxarsone in sterilized soils was only half of that in control soil, and the half life time of roxarsone was almost 3 times more than in control soil, which indicated that soil microorganisms played an important part in the process of roxarsone degradation in soils. The more the moisture and the temperature in soils were, the faster the degradation process of roxarsone occurred, the shorter the half time of roxarsone was. The average half time of roxarsone in soils was 115.0d,93.7d and 76.2d at 5℃,25℃and 35℃temperature respectively. At the 60%,40% and 20% soil moisture, the average half life time of roxarsone was 93.7d,104.3d and 130.9d respectively. The degradation rate and half time of roxarsone in soils with/without light was not obviously different, the average half life time was 84.4d and 93.7d.The exponential equation model was used to mimic the elimination of roxarsone in soils. When the concentration of roxarsone was 20,50 and 100mg/kg in soils, the degradating equations was C=16.0965e-0.0645t, C=39.0757e-0.0552t,C=78.7517e-0.0538t respectively and coefficients was more than 0.96, where C was content (mg/kg) of roxarsone in soil and t was the culture time (week). The average half life time of roxarsone in soils was 84.4d.On all accounts, soil microorganisms played an important part on roxarsone degradation in soils. Temperature and soil moisture significantly affected the degradation of roxarsone in soils. Light seemly played a certain role on the roxarsone degradation. The exponential model was imitated preferably the degradation of roxarsone in soils. The average half life time of roxarsone in soils was 84.4d and roxarsone may be degraded easily in the environment basis on the standard of half life time of pesticide.
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