沼液沼渣的施用促成農地環境抗生素抗性基因增殖的可能性確認與防治(1/4)

It is known that anaerobic digestion processes operated at ambient temperature and under mesophilic conditions are less effective in reducing the level of antibiotic resistance genes (ARGs) in livestock manure than composting; yet, the vast majority of husbandry farms in Taiwan have been using such systems to treat livestock excrement. To understand and assess the risk of the proliferation of ARGs in the environment via biogas slurry residues applied as fertilizers, in this study we attempt to address issues of 1) Is there seasonal differences in antibiotic resistance of biogas slurry residues produced from conventional anaerobic digestion? 2) What is the degradation rate of associating ARGs after biogas slurry residues are irrigated on farmland? 3) Would ARGs of biogas slurry residues have the same fate in the soil matrix as that of compost? 4) How can biochar derived from agricultural wastes be used as an effective tool to reduce and prevent the development of environmental antibiotic resistance? By far, through sample collection and analysis, as well as laboratory experiments, results of this 4-year research project have shown that: (1) No matter in which season (sampling at 33-38 C in summer and at 19-25 C in late autumn and early winter), both the absolute and relative abundances of ARGs of biogas residues produced from swine farms are generally higher than those of cattle farms; more importantly, the autumn/winter samples in average had higher ARG abundances than summer samples, implying that the application of the biogas residues obtained in winter as fertilizer for the first season crops may lead to the more elevated proliferation of antibiotic resistance in agricultural soil. (2) By incubating biogas residues and compost separately with the soil collected alongside a mountain trail for one month and using tetM, sul1, blaTEM, ermB, and intI1 respectively as the ARG and mobile genetic element (MGE) indicator genes, no significant difference, in terms of the degradation degree and rate of the gene abundance in soil, was observed between these two fertilizers, suggesting that when the frequency of fertilizer application is similar, biogas residues are more likely to cause the problem of antibiotic resistance accumulation in farmland due to a higher initial content of ARGs and MGEs. (3) Compared to biochar synthesized at 600 C pyrolysis, lower pyrolysis temperature (300 C) resulted in biochar having a higher adsorption capacity of heavy metals (zinc, copper, cadmium) and the performance of biochar derived from fallen camphor tree leaves was better than rice husk biochar; however, biochar prepared at 600 C pyrolysis otherwise stabilized metals in the soil better than lower pyrolysis biochar, indicating that deciduous biochar samples can be used to further explore their possibility of reducing the development of antibiotic resistance in the soil environment.