Monitoring of acetochlor residues in soil and maize grain supported by the laboratory study

The purpose of this work was to evaluate the acetochlor degradation rate in soils and investigate acetochlor contamination of maize grains and soil. Two kinds of soil: medium silty loam (soil A) and heavy loamy sand (soil B) were collected for the laboratory experiment. The degradation data were plotted. Good linearity was found between logarithmic concentration of acetochlor residues and time, indicating first-order rates of degradation. The t1/2 values varied from 10.5 days for soil A to 15.1 days for soil B. The degradation rate depends on the soil properties. In the soil A (higher content of clay and organic carbon) the t1/2 value was shorter than in the soil B. Monitoring tests were carried out during the 2010–2012 time period on maize fields located in the south-western Poland. Soil and maize grain samples were collected at harvest time. The determination of acetochlor residues was conducted using gas chromatography with electron capture detection. Based on the analysis of a total of 124 environmental samples, acetochlor residues were detected in 17.4% of soil and 8.1% of maize grain samples. None of the examined samples showed a herbicide concentration exceeding the maximum residue level.