Trifluralin residues in soils from main cotton fields of China and associated ecological risk

Trifluralin is a widely used dinitroaniline herbicide in cotton fields of China but is highly persistent in the environment and can act as a biotoxin and cause genotoxicity to terrestrial organisms, including humans. In this study, the concentrations and distribution of trifluralin residues in 139 soil samples from the major cotton-producing areas of China were investigated. The trifluralin concentrations ranged from ND (not detected) to 66.39 μg/kg dry weight (dw), with a geometric mean of 4.13 μg/kg dw. The detection frequency of trifluralin in Hebei (75%) was higher than that in Xinjiang (66%) and Shandong (40%), but the mean trifluralin concentration was highest in Xinjiang (5.98 μg/kg dw), followed by Hebei (5.06 μg/kg dw) and Shandong (3.19 μg/kg dw). No trifluralin residues were detected in cotton soil in Anhui, Jiangxi and Hunan. The residual amount of trifluralin in soil was significantly correlated with the soil organic matter content. The risk quotient method was used to evaluate the ecological risks associated with trifluralin. Results indicated that trifluralin in all the samples had a low risk to earthworms, but trifluralin in same cotton soils showed high risks to wheat, barley and lucerne. Overall, our work is helpful to understand the residual situation of trifluralin in Chinese cotton soil, to assess the environmental risk of trifluralin, and to control the use and safety of trifluralin in cotton field cultivation.