Characteristics Of Chlorpyrifos Removal And Microbial Community Structure Analysis In Tumen River Basin Wetlands Systems

With the development of the national economy and modern agriculture,pesticides have been widely used,which has caused great damage to the ecological environment,especially the environmental problems caused by agricultural non-point source pollution are becoming more and more serious.Constructed wetland system is widely used in the field of wastewater treatment because it has several advantages including simple operation,good decontamination effect,and achieving resources recycling utilization.And it has become one of the important means to degrade pollutants in water environment.In this study,the wetland plants in the Tumen River Basin were investigated and analyzed,the typical wetland plants were selected as the purification objects.And the hydraulic retention time,chlorpyrifos influent concentrations,chlorpyrifos volume loading and C/N as variables,characteristics of chlorpyrifos removal by wetlands systems under different operating conditions were investigated and analyzed,in order to clarify the mechanism of chlorpyrifos remove by plants,matrix and microorganism;simultaneously,combined with high-throughput sequencing technology,the effects of chlorpyrifos influent concentrations on microbial community structure in the system were investigated,and the influence of chlorpyrifos on the system was analyzed from the microbiological point of view.The following conclusions were drawn from the study:1)The distribution of A.calamus in the Tumen river basin was relatively concentrated,strong vitality,strong adaptability to the environment,and high resistance to stress and purification ability for conventional pollutants.At the same time,A.calamus had good economic and ornamental value.So,A.calamus was selected as the purification object to purify the organophosphorus pesticide chlorpyrifos.2)The effluent concentration of chlorpyrifos in wetland systems first decreased and then increased with the extension of HRT.When HRT was 7 d,the lowest value appeared;while HRT was 1 d,degradation range of chlorpyrifos concentration was the maximum.The removal efficiency and removal rate of chlorpyrifos first increased and then decreased with the extension of HRT,and the highest value was found at 7 d.Therefore,selected 7 d as the optimum HRT for chlorpyrifos degradation.3)In the wetland system,the removal of chlorpyrifos was accomplished by the combined action of substrate adsorption,plants absorption,and microbial degradation;however,with different influent concentrations of chlorpyrifos,there were significant4)differences in chlorpyrifos removal by substrate,plants,and microbes in the system.At the same time,in the CW1,CW2,and CW3 wetland systems,the substrate,plants,and microbes also had different effects on chlorpyrifos removal.5)Within the range of influent concentration of chlorpyrifos from 0.48 to 0.96mg/L,chlorpyrifos concentrations had a significant impact on the microbial community richness of the system.When the chlorpyrifos concentration was 0.48 mg/L,the microbial community richness was the highest in the system.In addition,in the wetland systems,Proteobacteria and Acidobacteria were the main bacterial phylum removing chlorpyrifos.6)The degradation and absorption of chlorpyrifos by water,matrix and plant in the wetland systems decreased with the increased of the chlorpyrifos volume loading from 13.24 to 22.06mg/m3/d.The chlorpyrifos volume loading was 13.24mg/M3/d,the removal effect of chlorpyrifos by wetland systems achieved optimal,and activities of matrix enzyme were the highest at this time;simultaneously,both urease and TN removal efficiency,alkaline phosphatase and TP removal efficiency were significantly positively correlated in systems.7)The degradation and absorption of chlorpyrifos by water,matrix and plant in the wetland systems increased with the increased of the C/N from 2 to 20.The C/N was 20,the removal effect of chlorpyrifos by wetland systems achieved optimal,and activities of matrix enzyme were the highest at this time;simultaneously,both urease and TN removal efficiency,alkaline phosphatase and TP removal efficiency were significantly correlated in systems.