Occurrence, distribution and ecological risk assessment of antibiotics in Nanming river: Contribution from wastewater treatment plant and implications of urban river syndrome

To study the occurrence and spatial distribution of antibiotics in the Nanming River in Guiyang, China, 27 water samples were collected. Twelve antibiotics were analyzed by solid phase extraction (SPE) combined with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), among which a total of eight antibiotics were detected with a maximum frequency of 91.2%, indicating the prevalence of antibiotics in the study area. The total antibiotic concentrations ranged from 2.3 to 1097.4 ng/L and were dominated by fluoroquinolones according to wide spatial distribution. The least contaminated sites were located in suburbs, while the most severe contamination occurred in sites affected by urban areas. The spatial distribution is vulnerable to human activities such as wastewater treatment plants (WWTPs). The self-organizing map (SOM) atlas showed that antibiotics were mainly divided into three components: sulfonamides (SAs), tetracyclines (TCs), and fluoroquinolones (FQs), and the sampling sites were divided into four categories. Ofloxacin (OFX) was the dominant contributor to ecological risk with the risk quotient (RQ) > 1 at 23 sampling points. The good positive correlation between FQs and Na+/ (Na+ +Ca2+) implied that FQs could be used as a symbol of urban river syndrome. By combining traditional indicators and emerging pollutants (co-tracers), this study provides a more accurate representation of anthropogenic pollutants in urban rivers.