| Atrazine is a kind of herbicide widely used during corn planting.However,the residual atrazine in the soil will cause phytotoxicity to the following legume crops,and then cause rotation obstacles.In this study,soybean which was seen as a sensitive crop of atrazine was selected as the research object.Based on the comparison of the typical growth and physiological characteristics of soybean under the stress of atrazine residued in different types of soil（chernozem and loess）,the environmental behavior of atrazine in the above-mentioned different types of soil and the difference of the binding capacity of soil soluble organic matter and atrazine were further discussed,in order to explain the relevant mechanism of the difference of plant toxicological effects which caused by atrazine in different types of soil from the perspective of environmental behavior and bioavailability of pollutants.The main results are as follows:（1）The adsorption kinetics test showed that the adsorption of atrazine on chernozem and loess reached equilibrium at 18h.The adsorption capacity of chernozem and loess were 36.263 mg·kg-1and 29.740 mg·kg-1 respectively.The quasi-second-order kinetic model is more suitable for the adsorption process of atrazine on chernozem and loess.The results of isothermal adsorption experiments show that the adsorption process of atrazine in chernozem and loess can be fitted with Langmuir model in 25℃.For atrazine solution of the same concentration(5 mg·L-1-30 mg·L-1),the adsorption capacity of chernozem to atrazine is always higher than that of loess,indicating that the adsorption capacity of chernozem to atrazine is stronger than that of loess.（2）According to the three-dimensional fluorescence spectrogram,the soluble organic matter（DOM）of both soils contain substances similar to humus.As the concentration of atrazine increased from 0 mg·L-1 to 30 mg·L-1,the fluorescence intensity of DOM in chernozem and loess decreased significantly,which indicated that DOM extracted from chernozem and loess showed good ability of combining with atrazine,and the affinity of DOM in chernozem to atrazine was stronger than that in loess.（3）Atrazine residued in soil have toxic effects on soybean growth and can seriously inhibit its growth and development.When the concentration of atrazine was 5-12.5 mg·kg-1,the effect of inhibiting the growth of soybean seedlings increased with the increase of atrazine concentration.In chernozem and loess,the plant height decreased by 17.3%-37.8%and 24.1%-45.3%,the root length decreased by 5.9%-27.0%and 3.0%-42.1%.Under the same exposure concentration,the content of photosynthetic pigment in chernozem was always higher than that in loess,which showed that the color of soybean seedling in loess was more yellow than that in chernozem..The net photosynthetic rate,transpiration rate and stomatal conductance of soybean leaves in chernozem and loess were in inverse proportion to atrazine concentration and in direct proportion to light radiation intensity.The MDA content in chernozem and loess increased gradually with the increase of atrazine stress concentration,and the MDA content in soybean leaves in chernozemwas always lower than that in loess,which indicated that the membrane lipid peroxidation of soybean seedlings was induced by atrazine stress,the cell microstructure was damaged,and the residual atrazine in chernozem was more stressful and more toxic to soybean than that in loess.Along with the damage of active oxygen,many antioxidant enzymes in soybean seedlings have been activated correspondingly,the activities of SOD,POD,CAT and APX in both soils show the trend of low concentration promoting high concentration inhibition.When the concentration of atrazine was 10 mg·kg-1,the activities of SOD,POD,CAT and APX of leaves and roots in chernozem reached the maximum value,while those in loess reached the maximum value at 7.5 mg·kg-1. |
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