Studies on the effects of biochar application on variation of heavy metals and antibiotic resistance genes
This study investigated the effects of corn straw biochar(CB)and rice husk biochar(HB)on heavy metal passivation efficiency and resistance genes reduction during anaerobic digestion(AD)of swine manure(SM).This study also investigated the main factors affecting the fate of antibiotic resistance genes(ARGs)during AD of SM.The addition of biochar CB and HB could promote the conversion of Cr,Cu,Pb,and Zn into more stable metal forms,and adding HB had a better heavy metal passivation effect.The addition of CB and HB reduced the absolute abundance of ARGs to varying degrees,and the removal efficiency of extracellular resistance genes(eARGs)was ranging from 55.6％to 98.3％.HB with a larger specific surface area could adsorb more extracellular resistance genes.The changes of intracellular resistance genes(iARGs)were less affected by biochar,and iARGs reduction was mainly related to the removal of potential host bacteria.The change of microbial community structure(λ=0.83,P＜0.01)and MGEs(λ=0.60,P＜0.05)were the main factors affecting the fate of ARGs.The addition of biochars were not directly affect the fate of ARGs(λ=0.29,P＞0.05).The addition of biochar reduced the content of bioavailable metals,thus reducing selective pressure in the AD.And the addition of biochar altered the microbial population structure and reduced the abundance of MGEs and MRGs,thus indirectly promoting the removal of ARGs during AD.
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