Identification of indicators of antibiotic pollution in typical karst groundwater in southwestern China

Objective The karst area in southwestern China is one of the three concentrated karst distribution areas in the world. Karst groundwater is highly susceptible to pollution from the surface due to the unique structure of aquifers. Methods To investigate the dominant factors influencing the spatial distribution of antibiotic pollution, clarify the correlation between antibiotics and hydrochemical parameters, and then identify the indicators of antibiotic pollution in karst groundwater systems, a typical karst groundwater system in southwestern China was selected as the research object. Thirty-five antibiotics were analysed using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Results The results showed that a total of thirty antibiotics were detected in the study area, including 3 tetracyclines (< MDL -421 ng/L), 5 macrolides (28.3-884 ng/L), 9 sulfonamides (2.50-30 ng/L) and 13 quinolones (19.5-1 807 ng/L).Among them, macrolides and quinolones were the dominant antibiotics in the study area, whose spatial distribution was dominated by pollution sources and dilution effects. The results of Pearson correlation analysis showed that the concentrations of inorganic nitrogen (the sum of NH4+-N, NO2--N and NO3--N), total organic carbon (TOC), Na+ and Cl- were significantly positively correlated with the concentration of individual antibiotics, the concentration of various antibiotic species, and the total concentration of antibiotics (r=0.81-0.99, p < 0.05, N=7-8). With more stable properties than inorganic nitrogen, TOC and Na+, Cl- is a more reliable indicator of antibiotic pollution in groundwater in karst areas. Conclusion This study provides a theoretical basis for the identification and prediction of antibiotic pollution in karst areas affected by county-level wastewater treatment plants (WWTPs) and rural domestic wastewater discharges.