Iron-modified Biochar Loaded Acinetobacter Lwoffii DNS32 For Enhanced Degradation Of Atrazine

Atrazine is a persistent organic pollutant that is not easily degraded in the soil and enters the water environment.Its use is accompanied by great dangers and poses a threat to many plants and animals.Biodegradable atrazine has received extensive attention due to its environmental friendliness and thorough degradation.However,some environmental variables in contaminated soils(including soil physical and chemical properties and organic pollutants)can cause significant changes in microbial communities that may result in loss of activity of some functional bacteria.Biochar is an inexpensive material with well-developed pore structure,strong adsorption capacity and high environmental stability.If biochar is used as a carrier for degrading bacteria,this damage can be alleviated and functional bacterial activity can be increased.Based on a large amount of literature research,this study prepared biochar(BC)and iron modified biochar(Fe MBC).The adsorption properties of BC and Fe MBC were studied.Then the degradation characteristics of two kinds of biochar-loaded DNS32 strains on atrazine and the effects of BC and Fe MBC on the activity of DNS32 were studied.Finally,iron-modified biochar-loaded DNS32 microbial agents were added to the atrazine-contaminated soil to study the degradation of atrazine by DNS32 bacteria and its impact on microbial communities,providing new opportunities for the development of environmentally friendly new materials.Through the above research,the following conclusions were obtained.(1)SEM,FTIR,XPS and XRD were used to characterize BC and Fe MBC,and the adsorption behavior of BC and Fe MBC on atrazine was studied.The results show that BC retains the natural microstructure and Fe MBC has the same structure as BC.However,the surface roughness of Fe MBC is higher than BC.Fe BMC surface functional groups are more abundant than BC.Both BC and Fe MBC conform to the pseudo second-order kinetic model,indicating that the rate-limiting step for the adsorption of atrazine by BC and Fe MBC is chemisorption.The adsorption isotherms of BC and Fe MBC are in accordance with the Langmuir equation.The qmax values of BC and Fe MBC for atrazine are 34.043 mg/g and 40.315 mg/g,respectively,indicating that the adsorption performance of Fe MBC is better.(2)The optimal time for biochar adsorption of DNS32 strain was discussed.The characterization of DNS32 strain was carried out by SEM and TEM.The results showed that the optimal adsorption time of biochar-loaded DNS32 strain was 30 min.The SEM results showed that the DNS32 strain could enter the biochar freely.TEM results showed that the cell membrane of the DNS32 strain loaded on the biochar material was intact.(3)The biodegradation kinetics of DNS32 microbial agents was studied to analyze the mechanism of atrazine removal.The effects of BC and Fe MBC on the growth and biofilm formation of DNS32 strains were studied.At the same time,the interaction between extracellular polymer(EPS)and atrazine was explored.The results show that BC and Fe MBC promote the biodegradation of atrazine,and the zero-order kinetic model fitting of DNS32 bacterial degradation kinetics indicated that the removal of atrazine was dominated by biodegradation.BC and Fe MBC have a significant promoting effect on the growth of the DNS32 strain.In the presence of Fe MBC,the DNS32 strain first entered the log phase of growth.Both BC and Fe MBC can promote the formation of biofilm of DNS32 strain.Due to its rough surface suitable for adhesion of bacterial membranes,Fe MBC surface bacteria form the most biofilms.Three-dimensional fluorescence spectroscopy and simultaneous fluorescence spectroscopy indicate a strong interaction between atrazine and EPS,mainly because the protein is obviously quenched by atrazine,and the quenching process is static fluorescence quenching.(4)The degradation of Atrazine in soil and the effect on microbial community by Fe MBC-loaded DNS32 reagent(b Fe MBC)were studied.The results showed that b Fe MBC significantly enhanced the degradation of atrazine in soil.High-throughput sequencing results showed that the addition of b Fe MBC restored the abundance and diversity of microbial species in contaminated soils,and mediated the dynamic changes of bacterial gates.Atrazine reduced most of the genus in contaminated soil compared to uncontaminated soil treatment,but the addition of b Fe MBC effectively mitigated this change.The PCA for the genus members was conducted to analyze the community changes in different treatments.The difference in soil flora was significant.Most of these increased genus belong to plant growth-promoting bacteria or pollutant-degrading bacteria.The increased genera may be responsible for promoting biodegradation of atrazine.