Research On Preparation And Application Of Solid Waste Biochar From Mariculture And Its Effect On Soil Microorganisms

Land-based mariculture with high stocking density usually produces excessive eutrophication,residual bait,excreta and antibiotics,and due to the limitation of technology and salinity,the proper and effective treatment of these wastes is still an open question.biochar materials,with the advantages of low-cost materials and large specific surface area(SSA),are currently used in pollutant adsorption,soil amendment and Biochar materials have the advantages of low-cost materials and large specific surface area(SSA),and have great potential for applications in pollutant adsorption,soil improvement and microbial community regulation.In aquaculture systems,the collection of residual bait and excreta provides further advantages in waste reuse and environmental protection when transformed into biochar.Therefore,research on the development and application of biochar based on mariculture solid waste is necessary to develop mariculture-based Therefore,it is necessary to develop biochar materials based on mariculture solid waste and explore their potential applications in microbial improvement,water treatment,and agricultural soil.In this paper,biochar and modified biochar were prepared by direct pyrolysis and metal salt modifiers,and their physicochemical properties,water pollutant removal,saline soil improvement and the effects of soil microbial diversity and microbial community structure were investigated,specifically including the following results:Firstly,in this study,the residual bait and manure biomass feedstock of mariculture fish were prepared into biochar by pyrolysis at 300℃,500℃,700℃,800℃,and 900℃,respectively,noted as BC300,BC500,BC700,BC800,and BC900,and modified with zirconium or iron(BC700-Zr or BC700-Fe),and the physicochemical properties of the residual bait and manure biochar were characterized.The physical and chemical properties of the residual bait manure biochar were characterized under different pyrolysis temperature gradients and different modifiers.The results showed that the ash content increased significantly and the yield decreased gradually with the increase of pyrolysis temperature.Elemental analysis showed that the aromaticity of biochar was relatively little affected by the pyrolysis temperature,and the hydrophilicity and polarity of biochar weakened with the increase of temperature in a certain temperature range.Infrared spectrograms exhibited that 500℃ and modification could improve the-OH functional group.It was found that higher pyrolysis temperature could improve the porosity and further increase the specific surface area,and BC700-Zr had the highest specific surface area among the modified biochars.Then,this study investigated the removal of nitrogen and phosphorus nutrients and antibiotics from water bodies by residual baited manure biochar.The results showed that the biochar BC700-Zr and BC700-Fe had high denitrification efficiency.The biochar exhibited nitrogen and phosphorus desorption,while BC700-Zr and BC700-Fe showed no significant phosphorus desorption.The adsorption kinetic analysis showed that the adsorption processes of nitrate,nitrite and enrofloxacin were consistent with the quasisecondary model,while those of ammonia nitrogen and phosphate were more consistent with the quasi-first-order model.Biochar exhibited nitrogen and phosphorus nutrient release,which has potential application in saline land improvement.Multiple linear regression analysis showed that nitrogen release was closely related to the nitrogen content,p H and mean pore width of biochar.Phosphorus release was negatively correlated with p H and positively correlated with mean pore width.This study also explored the effects of residual bait manure biochar on fertility,nutrient effectiveness and soil enzyme activity of saline soils under different charcoal application rates and with or without plants.In this study,potting experiments were conducted on saline soils with or without plants treatment(with plants,+P;without plants,-P)and biochar gradient treatment groups(0%;1%;3%;5%;biochar/soil weight),respectively.The results showed that biochar reduced soil salinity and increased soil total carbon(TC),total nitrogen(TN),fast-acting phosphorus(AP)and fast-acting potassium(AK)contents,but had little effect on soil p H.biochar addition increased soil organic carbon,soil NH4+ and NO3-,microbial mass carbon and soil enzyme activity.overall,a suitable biochar percentage(3%)in saline soils and plant In general,the appropriate biochar percentage(3%)and the integrated use of plants may be an effective strategy to improve soil salinity,soil nutrients and enzyme activity.Finally,based on the saline-alkali soil improvement experiment,this study used 16 S r DNA amplicon sequencing analysis and other techniques to study the effect of biochar on microbial diversity and microbial community structure in saline-alkali soil.16 S r DNA amplicon sequencing analysis showed that the addition of biochar increased the abundance of some functional bacterial genera,and Alpha diversity analysis showed that biochar could affect the community richness and diversity of soil microorganisms.In conclusion,adding biochar indirectly affects soil microbial bacterial community by changing soil physicochemical properties(soil microbial biomass carbon,available phosphorus,available potassium,total organic carbon,total nitrogen,etc.).Different carbon application gradient levels had different effects on the microbial community,while the differences in the effects of different sampling times on the soil microbial community in the short term were inconsistent.Biochar can affect soil microbial abundance and diversity,and change the distribution of soil bacterial populations,which may lead to changes in soil system function.