Effects Of Coal Gasification Slag On Antibiotic Resistance Genes During Agricultural Waste Composting

The abuse of antibiotics in livestock and poultry farming leads to high concentrations of antibiotic residues in livestock manure,and induces the production of antibiotic resistance genes(ARGs)in the environment.ARGs can cause resistance to human pathogens through mobile genetic elements(MGEs),resulting in the loss of efficacy of antibiotics and threatening human health.Aerobic composting is the main means of harmless treatment and resource utilization of livestock manure.However,the agricultural use of compost products has become an important way for ARGs to enter the soil.Coal gasification slag(CGS)is an inevitable by-product of industrial production,with a porous structure,a large specific surface area and good adsorption properties.Therefore,using different proportions of CGS(0%,5%,and 10%)as additives,and to investigate the effects of CGS on the compost material chemical properties,ARGs and MGEs gene abundance and bacterial communities,and the relationships among MGEs,environmental factors,bacterial communities,and ARGs were also analyzed.The aim of this study was to explore the effects of CGS on the microbial communities and ARGS and to elucidate the underlying microbiological mechanisms.The main results and conclusions are as follows.(1)The three treatments of CK,L and H lasted for 4d,5d and 6d during the high temperature period.After the end of composting,all treatments had a C/N of less than 20 and a GI index of more than 80%,reaching full maturity.The addition of CGS can accelerate the start of composting system,prolong the high temperature period of compost,and enhance the degree of maturity.In addition,the addition of CGS improves the passivation effect of compost on bio-Cu and bio-Zn,especially 10% CGS.(2)Aerobic composting reduced the abundance of dfrA7,tetW,ermX,qnrS,aac(6')-ib-crs,intI2,ISCR1 ? Tn916/1545 in pig manure by 0.24–1.49 logs,respectively.And with the increase of CGS addition ratio,the removal efficiency of ARGs and MGEs in compost increased.Compared with CK,10% CGS effectively prevented the enrichment of some ARGs and intI1 in compost products.(3)Firmicutes,Proteobacteria and Actinobacteria are the main categories in the composting process.Composting time dominates the changes in microbial community structure.RDA analysis indicated that bacterial communities and MGEs were the main causes of abundance changes in ARGs in compost.Network analysis revealed potential host bacteria for 14 ARGs.CGS can reduce the Horizontal gene transfer by reducing theabundance of MGEs,and reduce the potential host bacteria of ARGs,improve the removal efficiency of ARGs,and reduce the risk of ARGs in compost products.In summary,coal gasification slag can accelerate the composting process,promote compost maturity,and reduce the content of bioavailable Cu and Zn in compost products.10% coal gasification slag has the best effect on the reduction of ARGs and MGEs in compost.Bacterial communities and MGEs are the main causes of abundance changes in ARGs during composting.The research conclusion provides a theoretical basis for the application of coal gasification slag in composting.