Remediation strategy of biochar with different addition approaches on antibiotic resistance genes in riparian zones under dry wet alternation.

The global prevalence of antibiotic resistance genes (ARGs) has aroused increasing concern due to its threat to ecological security and human health. Although biochar has been widely used for pollution remediation including ARGs, little is known its regulation on antibiotics and ARGs propagation under riparian zones, where undergo frequent occurrence of dry and wet alternations (DWA) caused by water-level fluctuation. Therefore, this study investigated the regulative effects of biochar through different addition approaches on ARGs spread in riparian zone sediments. Under DWA, the presence of biochar (2 % w/w) inhibited microbial diversity and function expression, especially for tiled biochar. In addition, compared with DWA, the tiled biochar decreased ARGs abundance by 45.36 %, while the well-mixed increased that by 269.02 %. The ARGs abundance in sediments was positively correlated with mobile genetic element abundance (R=0.996, p < 0.05), indicative of high horizontal gene transfer potential of ARGs. Metabolomics revealed that both DWA and biochar significantly altered microbial metabolism pathways in sediments, involving sulfur metabolism and histidine metabolism. Furthermore, ARGs propagation in riparian zones may be dominantly driven by MGEs, especially by transposases and integrase. These findings highlight the tiled biochar remediation effects on ARGs in riparian zones under DWA caused by global warming.