Study On The Characteristics Of Bacterial Community And Environmental Factors In The Removal Of ?-HCH In Constructed Wetlands

Organochlorine pesticide is a typical persistent organic pollutant in the environment,which has the characteristics of high toxicity,persistence,bioaccumulation and long-distance migration.In recent years,with the increasing detection of organochlorine pesticides in the natural environment by domestic and foreign researchers,it is found that higher organochlorine pesticide residues can still be detected from all kinds of environments,in which ?-HCH accounts for a higher proportion in the detection results,which has attracted worldwide attention.At present,studies show that constructed wetlands have great potential to reduce pesticides,suspended solids,nutrients and other pollutants in agricultural runoff.In this paper,four kinds of vertical subsurface flow constructed wetland devices with different plants were constructed.The removal process of ?-HCH by plants and microorg-anisms was studied.The coupling relationship between the change of microbial community structure and the degradation of ?-HCH was analyzed by high-throughput sequencing.In addition,combined with the changes of environmental factors in the operation of constructed wetland,the impact on pesticide removal was analyzed.The main conclusions are as follows:(1)The average removal rate of ?-HCH in the constructed wetland system in two seasons by different plants is 90.86% ? 98.17%.The adsorption of the substrate is the main way to remove ?-HCH in the constructed wetland water.The microbial inhibitors had a greater effect on the removal of ?-HCH in the matrix.The wetland content of the group with added microbial inhibitor was 0.83 ? 4.26?g / kg higher than that of the group without added microbial inhibitor.The BCF values of different plants are significantly different(P <0.05).In both seasons,canna canola has the largest contribution to ?-HCH absorption.Canna showed the best removal effect in winter,and the calamus showed the best removal effect in summer.In summer,constructed wetlands can remove ?-HCH more effectively.(2)The analysis results of the bacterial community diversity index showed that there was no significant difference in the microbial diversity index in each stage of winter.The summer mainly showed an increase compared with that before ?-HCH was not added.The Chao1 and Ace indexes that could be detected in the two seasons had Significant difference(P<0.05),bacterial community diversity from high to low are canna,calamus,Zaili flower,plant-free group,barracuda.A total of 80 samples were obtained through high-throughput sequencing of 77 phyla,96 class,177 orders,311 families,704 genera and 482 species.In terms of the composition of the bacterial community phylum,it mainly includes Proteobacteria,Green Bay phylum,Acidobacterium phylum,Hexabacterium phylum,Actinomycetes,Thick wall phylum.The genus level varies greatly between winter and summer.The Bacteroides and Actinomycetes,Bacillus and Sphingospora have better resistance to ?-HCH sewage than other bacteria.It may play an important role in the removal of organochlorine pesticide ?-HCH.The bacterial community structure of constructed wetlands in winter is quite different,and in summer,the bacterial community structure at the same stage is less different.From the perspective of plant species,the difference of Zailihua Wetland is the smallest,followed by Barracuda,and the biggest difference is between Calamus and Canna.(3)Spearman analysis of environmental factors and bacterial diversity index showed that the main environmental factors affecting bacterial diversity in constructed wetlands were temperature,DO,?-HCH in soil,and pH.Temperature,?-HCH in soil,?-HCH in water,and DO are the main factors that affect the distribution of the main genus bacteria in winter constructed wetlands.?-HCH,DO in soil,TP in soil,and ?-HCH in water affect summer.