Mechanism for various phytotoxicity of atrazine in soils to soybean: Insights from soil sorption abilities and dissolved organic matter properties

The pollutants in soils with different physicochemical properties usually exhibit various phytotoxicity due to their diverse environmental behavior. However, it is not clear that some components of dissolved organic matter (DOM) in soil affect the bioavailability of pollutants. In this study, the different phytotoxicity of atrazine in two different soils, black soil (BS) and yellow brown earth (YBE), to soybeen seedlings was investigated, and the potential mechanism were further discussed by examining the adsorption properties of atrazine with BS and YBE as well as the fluorescent characteristic variation of these two kinds of DOM extracted from BS and YBE during binding with atrazine. The results suggest that atrazine showed different phytotoxicity to soybean seedlings grown in BS and YBE. Specifically, the EC50 of atrazine on plant height and root length of soybean seedling in BS were 23.44 mg kg(-1) and 54.29 mg kg(-1), while those in YBE were 12.79 mg kg(-1 )and 21.48 mg kg(-1). The adsorption amounts of BS and YBE was 41.56 mg kg(-1) and 32.95 mg kg(-1). In addition, 3D-EEM showed that humic acid-like substances were the main components of DOM in the two soils. With the increase of atrazine concentration, the fluorescence of these two kind of DOM was gradually quenched, but DOM-BS had a faster quenching rate. FT-IR showed that DOM-BS contained more polysaccharides and richer lipophilic groups. Meanwhile, the results of PARAFAC found that DOM-BS was easier to combine with atrazine. The findings of this study are significant to reveal phytotoxicity of atrazine in BS and YBE. The above results are helpful to better understand the components of DOM in different soils and their different role in regulating the environmental behavior and phytotoxicity of organic pollutants.