Occurrence and risk assessment of three chloroamide herbicides in water and soil environment in northeastern, eastern and southern China

Chloroamide herbicides can cause adverse effects on nontarget organisms, but there is limited information about their occurrence in the environment of major cropland growing regions. In this study, a total of 1012 soil samples, 617 surface water samples and 737 groundwater samples were collected from 2020 to 2021 in three regions of China to evaluate the occurrence and risk of three important chloroamide herbicides alachlor, acetochlor and butachlor using the improved QuEChERS extraction method and high performance liquid chromatography-mass spectrometry. The results showed that residues of the three chloroamide compounds in surface water and groundwater ranged from 0.1 to 176.0 μg L−1, of which acetochlor was frequently detected from surface water (17.5%). As for the soil, mass fraction was varied between 1.0 and 1540.3 μg kg−1, similarly acetochlor had the highest detection frequency (49.6%). Timewise, the median mass fraction of selected chloroamide herbicides in soil in 2021 (7.8 μg kg−1) was significantly lower than that in 2020 (10.9 μg kg−1). Spatially, there were regional differences in the content of environmental residues, and the overall level of residues in the northeast was relatively high. The environmental risk assessment based on the improved Risk Quotient (RQ) method indicated that the selected herbicides were currently within an acceptable range for human health risks in the soil and water environment in various regions, but acetochlor and butachlor had contributed to the RQ values of fish and earthworms (0.01＜RQ＜0.1) in recent years, respectively, which might pose a certain risk of oral exposure to aquatic and terrestrial organisms. This study provides valuable data and ideas for the rational application, pollution control and environmental safety evaluation of chloroamide herbicides in China.