The influence of soil sorption of diuron on its toxicity to zebrafish embryos was investigated.Results showed that the sorption of diuron by soil occurred via a partition process,with a log Koc of 2.19.Diuron was moderately toxic to zebrafish embryos.From the observed hatching rates of embryos,the calculated EC50 value of diuron in soil-free solutions following a 72h exposure was 4.99 mg/L,along with a strong teratogenesis.Soil sorption effectively reduced the solution-phase concentrations of diuron in soil-water systems.Based on the total concentrations of diuron in soil-water systems,soil sorption increased the EC50 value of diuron to 7.53 mg/L.In comparison,the solution-phase concentration-based EC50 value of diuron was 4.75 mg/L,similar to the EC50 value obtained using soil-free solutions.It could be concluded that the soil sorption effectively reduced the toxicity of diuron to zebrafish embryos,and sorbed diuron virtually lost its toxicity.