Adsorption Of Atrazine On Black Soil By Biochar And Its Effects On Microbial Diversity

Because of its special structural characteristics and good adsorption properties,biochar shows excellent value in soil improvement and environmental pollution restoration.Biochar plays an important role in controlling the migration and accumulation of pollutants in the soil.In this dissertation,wheat straw derived biochars with different pyrolysis temperatures were used to investigate how the addition of biochar to the soil affected the atrazine adsorption and microbial degradation.In order to explore the effects of soil composition,soil samples?ST and HT?with different organic content were collected from typical agricultural lands,characterized by black soil in northeast China.The basic adsorption characteristics of wheat straw biochar prepared at different pyrolysis temperatures?350,550,700??were analyzed and applied to four different levels of added biochar?0.1%,0.5%,1.0%and 2.0%?.The adsorption performance of the soil with no added biochar and the soil with added biochar were compared.Through the culture experiment,atrazine was degraded in non-sterilized and sterilized soils,and the degradation rate of atrazine after the addition of biochar to the soil was also studied.The degradation of atrazine after biochar addition to soil was significantly enhanced,probably because biochar supplements can promote the growth and metabolism of microorganisms in the soil.Our results show that wheat-derived biochar may be an effective remediation agent that can activate the degradation of soil functional microbes,enhance the adsorption of organic matter content,and can be used to accelerate the recovery of Atrazine-contaminated black soil in an environmentally friendly manner.The effects of biochar on soil physicochemical properties and microbial diversity were also studied.Finally,high-throughput sequencing technology was used to elucidate the microbiological characteristics of biochar on black soil microbial community diversity.The main conclusions of the study are as follows:Three kinds of biochar with pyrolysis temperature were characterized in this experiment:elemental analysis showed that as the pyrolysis temperature increased from 350?to 700?,the carbon content in the biochar sample increased from 66.47%to 81.01%,indicating that the higher temperature resulted in higher The degree of graphitization.The surface area and pore volume of the biochar samples showed irregular changes,that is,BC550 obtained the largest surface area(195.46 m²·g^-1)and total volume(0.42 cm³·g^-1),and the specific surface area and total volume of BC350 had the minimum values.It is 19.76 m²·g^-1and 0.032 cm³·g^-1,which means superior porous structure resulting from carbonization at higher temperatures.The weight loss rate?64.94%?of wheat straw by thermogravimetric analysis mainly occurred at a temperature rise of 200-400?.Boehm analysis showed that a large number of acidic functional groups were observed on the surface of BC350.The functional groups were phenolic hydroxyl group?0.638 mmol·g-1?,carboxyl group(0.440 mmol·g^-1),and lactone group(0.124 mmol·g^-1).XPS analysis shows that the ratio of O/C and?O+N?/C decreases with the decrease of O-C=O as the pyrolysis temperature increases.The biochar samples at three different pyrolysis temperatures show reduced hydrophobicity and polarity.The adsorption kinetics of atrazine in the two soils in the whole adsorption process fitted with the pseudo-second-order kinetics model.The adsorption performance of ST soil?high organic matter content?was slightly higher than that of HT soil?low organic matter content?.The isothermal adsorption of atrazine by biochar at different additions of HT and ST samples was analyzed.Both were in accordance with the Freundlich model,and 2%of BC350+ST samples were added.When the C_e value was 13.55 mg?L^-1,the Q_e was 3.04 times higher than the blank soil?ST?.This paper also studied the degradation of atrazine in non-sterilized and sterilized soils.The results show that the addition of biochar greatly increased the atrazine conversion rate.In the absence of biochar,the atrazine conversion rate gradually slowed down,At 15 days,the atrazine conversion in the HT soil solution was 49.8%,and the ST soil was 95.62%.Compared with the results obtained from unsterilized soil,it was shown that soil organic matter can accelerate microbial transformation.In the simulation experiment of soil indoor,it was found that the content of soil organic carbon gradually increased with the extension of sampling time.At 43 d,the ST700 soil organic carbon was 6.71%.HT700 soil organic carbonwas 3.96%.it was shown that ST soil organic carbon content is higher than HT soil,soil was 1.23 times higher than the control ST soil,and HT700 soil was 1.34 times higher than the control HT soil.The content of soil microbial biomass carbon and nitrogen in each treatment soil was gradually reduced,and the amount of microbial nitrogen in the blank treatment at the end of the experiment?43 days?was significantly reduced.The content of soil microbial carbon and nitrogen in biochar was higher than that in blank soil.Based on high-throughput sequencing technology,the results of soil microbial community diversity showed that the Chaol,Ace,and Shannon indices are consistent.It shows that adding biochar can improve soil community diversity.