Estimating the bioavailability of acetochlor to wheat using in situ pore water and passive sampling

The intensive use of acetochlor in China leads to its extensive existence in soil which may result in contamination of crops and commodities. Therefore, it is vital to assess the bioavailability and phytotoxicity of acetochlor to crops. In this study, four measurements involved in in situ pore water extraction (CIPW), passive sampling extraction (Cfree), ex situ pore water extraction (CEPW), and organic solvent extraction (Csoil) were conducted to assess the bioavailability and phytotoxicity of acetochlor to wheat plant plants in five soils. The results showed that the acetochlor concentrations accumulated in wheat foliage and roots were in the range of 0.11–0.87 mg/kg and 0.09–2.02 mg/kg in the five tested soils, respectively, and had a significant correlation with the acetochlor values analyzed by CIPW (R2 = 0.83–0.90, p < 0.0001) or the Cfree method (R2 = 0.86–0.92, p < 0.0001). The acetochlor concentrations in the five soils measured by these two methods were also correlated with the IC50 values of acetochlor in wheat foliage and roots (R2 > 0.69, p ≤ 0.05). The results indicated that the CIPW and Cfree methods were effective in evaluating acetochlor toxicity to wheat and the acetochlor concentrations in wheat. The effects of soil physical and chemical properties including pH, organic matter content (OMC), clay content, and cation exchange capacity (CEC) on the acetochlor toxicity to wheat were analyzed, and soil OMC was found to be the dominant factor affecting the toxicity of acetochlor in the soil-wheat system.