| Wetlands are one of the three natural ecosystems on earth that play an important role in protecting biodiversity,improving water quality,regulating climate change and maintaining ecological balance.With the rapid development of livestock and poultry breeding industry in the world,the content of antibiotics and hormones in the aquaculture wastewater is increasingly high,while the absorption and metabolism of antibiotics and hormones in animals is limited.Antibiotics and hormones are widely detected in wastewater,soil,surface water and other water bodies.Sulfonamides,as typical antibiotic,have attracted extensive attention due to its residues in the environment and the increasing resistance in all organisms,and may bring serious health risks to humans and animals.Biochar and compost are two common remediation agents in polluted wetlands.Adsorption and degradation processes are the two important and closely related approaches to the remediation of organic pollutants in wetlands.The degradation of organic pollution is strongly relevant to the activities of soil ecosystem.At present,a lot of related researches on biochar and compost,however there are few literature surveying the effects of biochar-compost mixture to the wetland soil ecosystem(enzyme and microorganism)and the degradation and adsorption of soil organic pollutants.Therefore,there is little literature discussing the adsorption mechanisms of organic contaminant during wetland remediation.The main research contents of this paper are as follows:(1)the adsorption efficiency and desorption rate of sulfamethoxazole(SMX)in soils were surveyed after modified with different contents of biochar,compost and combined biochar-compost;(2)the basic properties,structural morphology(surface morphology,specific surface area,surface functional groups)and element composition of biochar/compost were analyzed to predict the adsorption mechanisms of SMX in modified wetland soil;(3)the degradation of SMX in soils were surveyed after the application of bio char,compost and combined biochar-compost during the remediation process;(4)enzyme activity and microbial biomass were determined during the remediation of organic pollution,and reveal ed its relationship with the degradability of SMX;(5)the different responses of bacterial communities and metabolic functions of the modified soil s were investigated after one month of cultivation.In terms of SMX adsorbability: Biochar had a higher specific surface area and a more developed pore structure than compost.Elemental analysis showed that biochar had higher aromaticity and hydrophobicity than compost.Compared with biochar,compost material had more abundant functional groups and high polarity characteristics.The adsorption capacity of the modified soils increased with the increase of the total amount of biochar and compost,which was consistent with the increase of the level of basic physicochemical properties of the soil s.Because the physicochemical properties of compost are higher,the effect of soil modification is greater.For the individual material treatments,biochar showed high er adsorption capacity.The study suggested that π-π interaction and pore filling were the main adsorption mechanisms for biochar,while hydrophobic distribution and hydrogen bonding were the main mechanisms for compost.The adsorption capacity of organic materials mainly depended on its morphological characteristics.For modified wetland soils,as small particles and other dissolved organic matters can block the pores of biochar,the pore filling of the experimental treatments applied with biochar will be greatly weakened.The adsorption capacity of the modified soils was mainly related to its basic physicochemical properties(p<0.05).The desorption rates of the biochartreated groups were usually lower than that of the biochar-treated groups,which also showed the different adsorption mechanisms of the two materials.In terms of SMX degradability: Compared with the control group,the degradation efficiency of 1% biochar(SB1)increased by 0.067%,which was mainly due to the increase of dehydrogenase and ur ease;the degradation efficiency of 5%biochar(SB5)decreased 0.206%,mainly due to the decrease in enzyme activity,especially dehydrogenase activity;in addition,due to the increase in enzyme activity and microbial biomass,2% compost(SC2),1% biochar & 2% compost(SBC3),10%compost(SC10)and 5% biochar & 10% compost(SBC15)increased the degradation efficiency by 0.033%,0.015% and 0.222%,respectively.The results revealed that the degradation efficiency was positively correlated with microbial bio mass and enzyme activities(p<0.05).High-throughput sequencing showed that the high-concentration treatments(SB5,SC10,SBC15)introduced more exogenous dominant strains and eliminated some inferior strains,thus increasing bacterial diversity and reduci ng bacterial abundance.The low-concentration treatments(SB1,SC2,SBC3)strengthened the dominant indigenous species and retained some inferior species,thus showing lower diversity and relatively high bacterial abundance.Compared with the low-concentration treatments,the high-concentration treatments increased the relative abundance of amino acid and lipid metabolizing genes,while decreased the relative abundance of carbohydrate metabolizing genes. |
