Occurrence and distribution of antibiotics in urban soil in Beijing and Shanghai, China

The recycling of reclaimed wastewater for irrigation and road cleaning is an important strategy to minimize water scarcity in megacities. However, little is known regarding the potential accumulation of antibiotics contained in reclaimed wastewater in urban soil. We investigated the occurrence and distribution of eight quinolones (QNs), nine sulfonamides (SAs), and five macrolides (MLs) antibiotics in urban surface soil in Beijing and Shanghai, China. QNs, especially norfloxacin (NOR), ofloxacin (OFL), and ciprofloxacin (CIP) were the predominant antibiotics in urban surface soil, and NOR revealed the highest average concentration of 94.6 μg kg(-1). The antibiotic concentrations in urban soil in our study were higher than those detected in agricultural soils after long-term wastewater irrigation and manure fertilization. The concentrations of antibiotics in Shanghai urban soil showed a significant negative correlation with soil pH and a positive correlation with total organic carbon (TOC), reflecting the effect of speciation and soil organic matter content on sorption and retention. In addition, antibiotic concentrations in the urban soil were positively correlated with heavy metal contents, likely due to their coexistence in reclaimed wastewater and the promoting effect of metals on the sorption of antibiotics. In several soil samples, NOR, OFL, CIP, enrofloxacin (ENR), and fleroxacin (FLE) showed higher concentrations than the trigger value of 100 μg kg(-1) in soil, indicating a potential risk for the environment.