Occurrence and removal of antibiotics and antibiotic resistance genes in natural and constructed riverine wetlands in Beijing, China.

Simultaneous elimination of antibiotics and antibiotic resistance genes (ARGs) is rarely investigated in full-scale riverine wetlands. Here, we compared the occurrence, abundance, and removal of 60 antibiotics and 27 ARGs in natural (Yeya Lake (YL)) and constructed (Bai River (BR)) riverine wetlands in Beijing, China. The concentrations of antibiotics in YL wetland were ND-51.9 ng/L in water and ND-37.9 ng/g in sediments. Significantly higher concentrations were found in BR wetland (ND-546 ng/L in water and ND-118 ng/g in sediments), which locates at the downstream of a reclaimed water treatment plant. The abundances of ARGs in YL and BR wetlands were up to 5.33 × 10 and 8.41 × 10 copies/mL in water, and 1.60 × 10 and 4.67 × 10 copies/g in sediments, respectively. These results suggest that wastewater greatly contributes to the elevated abundance of antibiotics and ARGs in both water and sediments. Compared to summer, higher levels of antibiotics in water were found in winter due to the higher usage, slower attenuation and the limited dilution. But higher abundances of ARGs were found in summer than in winter, in accordance with the favored microbial growth at higher temperature as denoted by copies of 16S rRNA. Compared to BR wetland, YL wetland achieved better removal of antibiotics and ΣARGs, with average removal efficiencies of 70.0% and 87.5%. Antibiotics, ARGs and environmental factors showed strong correlations in water samples from YL wetland. However, in BR wetland that receives urban wastewater effluents, no correlation between antibiotics and ARGs was found although the distribution of antibiotics was affected by aquatic environmental factors. These results indicate that subinhibitory concentrations of antibiotics may stimulate the prevalence of ARGs in natural wetlands.