Effect Of Organic Fertilizer Application On The Adsorption Behavior Of Atrazine In Black Soil

Atrazine is one of the herbicides commonly used in agricultural production in the black soil area of northeast China.Its residue in soil and its environmental behavior are the main factors that determine its negative effects on soil environment and sensitive crops.In addition,the application of organic fertilizer is generally considered as an effective measure to curb the degradation of black soil and improve the fertility of black soil.However,the effect of organic fertilizer application on atrazine adsorption behavior in black soil and its related mechanism still need further attention.In this study,the indoor simulation method was used to compare the adsorption behavior of atrazine in black soil after the application of different amounts of organic fertilizer.The response of soil aggregates,soluble organic matter ratio and composition to the application of organic fertilizer was further discussed.Combined with the binding characteristics of soil aggregates,soluble organic matter and atrazine,the relevant mechanism of organic fertilizer application to regulate the adsorption behavior of atrazine on black soil was preliminatively revealed.The main findings are summarized as follows:（1）The analysis of soil nutrients and surface characteristics showed that the content of organic matter in black soil treated with 3.25 g·kg^-1 organic fertilizer(OF1,equivalent to 7500 kg·ha^-1)and6.50 g·kg^-1 black soil(OF2,equivalent to 15000 kg·ha^-1)increased by 10.28%and 16.04%respectively compared with the treatment without organic fertilizer（CK）,reaching a significant difference level.Through scanning electron microscope and energy spectrum analysis,it was found that with the increase of the amount of organic fertilizer(0-6.50 g·kg^-1),the content of C element in the black soil increased from 0.99%to 13.1%,which was positively correlated with the amount of organic fertilizer.At the same time,the pores of the black soil surface structure gradually became larger and the particle structure enhanced.The results of infrared spectra showed that the addition of organic fertilizer could increase the content of lipophilic functional groups and oxygen-containing functional groups in black soil.The addition of organic fertilizer can adjust the mass proportion of soil aggregates of three particle sizes.Specifically,the proportion of 0.05-0.25 mm and 0.25-1 mm soil aggregates increased by 4.37%and 1.76%,and the overall proportion of 1-2 mm soil aggregates decreased by 6.13%.（2）The adsorption test results of soil aggregates with different particle sizes showed that the K_F values of soil aggregates with different particle sizes were in the order of 0.05-0.25 mm particle size>0.25-1 mm particle size>original soil>1-2 mm particle size.In addition,the correlation analysis between K_F and the mass proportion of soil aggregates with different grain sizes showed that the following conclusions could be drawn:organic fertilizer addition could improve the proportion of small soil aggregates with higher atrazine adsorption capacity of 0.05-0.25 mm and0.25-1 mm in black soil,and then improve the atrazine adsorption capacity of black soil.（3）The results of adsorption kinetics test showed that the maximum adsorption capacities of CK,OF1 and OF2 treatments for atrazine adsorption equilibrium were 33.798 mg·kg^-1,95.034mg·kg^-1 and 102.053 mg·kg^-1 respectively,indicating that the addition of organic fertilizer can improve the adsorption capacity of black soil for atrazine.The pseudo second order kinetics can better simulate the kinetic process of atrazine adsorption on the above three states of black soil.The results of isothermal adsorption test show that the Freundlich model can better describe the isothermal adsorption process of atrazine adsorbed by the above three states of black soil at room temperature of 25℃（R² is 0.969,0.984 and 0.991 respectively）.In the above three treatments,the K_F values of atrazine adsorbed by black soil were 3.223,3.726 and 7.230 L·kg^-1 respectively.The correlation analysis results between K_F and physical and chemical properties of black soil showed that the addition of organic fertilizer could improve the physical and chemical properties of soil and enhance the ability of atrazine adsorbed by black soil.（4）Three-dimensional fluorescence spectra showed that the main components of soluble organic matter（DOM）in the above three treatments were humus.In addition,all extracted DOM can bind atrazine to quenched their fluorescence peaks.However,the quenching speed of BLACK soil DOM treated by OF1 and OF2 is 1.4 times and 2 times that of CK,respectively.Parallel factor analysis further found that the content of humus in BLACK soil DOM treated by OF1 and OF2increased by 41.55%and 119.06%,respectively,compared with that treated by CK.