Study On The Environmental Behavior Of Atrazine On Typical Soils In Jilin Province Under The Coexistence Of Microplastics

When pesticides are applied in agricultural fields,a series of environmental behaviors such as adsorption,desorption,leaching,biodegradation and chemical degradation of pesticides by the soil can occur,which may cause certain hazards to the soil ecosystem.Polyethylene plastic film is usually not recycled after use,and residues in the soil over time can adsorb organic pollutants such as pesticides in the environment,which may exacerbate soil ecological risks.Therefore,this paper selects polyethylene（PE）,a widely used microplastic,and investigates the effects of adsorption,degradation and leaching of atrazine（AT）on three typical soils（black soil,black calcareous soil and white pulp soil（0-25 cm））in Jilin Province under the coexistence of PE in an indoor simulated environment,in order to assess the combined effects of microplastic and pesticide pollution on farmland ecosystems.The results were as follows The specific results were as follows:（1）Under the coexistence condition of 2.00%PE,the maximum adsorption of AT at a concentration of 10 mg·L^-1 was increased by 1.21,0.83 and 0.44 times for black soil,black calcium soil and white pulp soil,respectively,compared with the soil without PE addition;the desorption rate decreased by 12.45,6.03 and 11.80%,respectively,compared with the three soils without PE addition.The isothermal adsorption characteristics were more in line with the Freundlich isothermal adsorption equation model,and the adsorption capacity K_f increased by2.11,1.01 and 0.91 times,respectively,compared with the soils without PE addition.（2）Under the conditions of PE coexistence,the thermodynamic fitting parametersΔG^θ<40k J·mol^-1 andΔH^θ<40 k J·mol^-1 and the thermodynamic parameter valueΔS^θ<0 for AT adsorption in the three soils indicated that the adsorption process was physical adsorption and was spontaneous exothermic reaction with decreasing adsorption confusion;the adsorption capacity of AT adsorption in the three soils increased with the decrease of PE particle size and the addition of PE.The equilibrium adsorption capacity of AT in the three soils increased with the decrease of PE particle size and the increase of addition;it became weaker with the increase of Ca²⁺and K⁺concentration in the solution,and Ca²⁺inhibited the adsorption capacity of AT more than K⁺as the concentration increased;the equilibrium adsorption capacity of AT in the three soils decreased gradually with the increase of soil pH,and the equilibrium adsorption capacity of AT decreased more rapidly in the alkaline soil;the cationic surfactant CTAB promoted the adsorption of AT in the three soils,and the adsorption capacity decreased with the increase of CTAB.The cationic surfactant CTAB promoted the adsorption of AT in the three soils,and the adsorption amount increased with the increase of CTAB concentration.（3）The degradation characteristics of AT in typical soils in Jilin Province were investigated by indoor incubation tests under PE coexistence conditions.The results showed that the degradation rate of AT in black soil was the largest and the shortest half-life was 38.5 d.The half-life time was extended after sterilization in all three typical soils,indicating that microorganisms in the three typical soils played a role in the degradation of AT;the coexistence of PE increased the residual amount of AT in the three soils and extended the half-life of AT in the three soils.The simulated leaching test in soil column showed that the lowest leaching rate in black soil and the highest leaching rate in white pulp soil under PE coexistence condition.The presence of PE inhibited the vertical migration of AT in the soil compared with the soil without the addition of microplastics,and the inhibition ability became stronger with the increase of PE content.The addition of straw biochar prolonged the half-life of AT degradation in the soil and weakened the downward leaching ability than that with microplastics,which aggravated the contamination of AT in the surface soil.