Contamination Characteristics And Risks Assessment Of Antibiotics In Four Typical Surface Waters In Nanchang

Antibiotics are widely used for the prevention and treatment of human and animal diseases. With the increasing of population, the scales of livestock husbandry and aquaculture continue to expand. As a consequence the types, productions and usages of antibiotic are also increasing rapidly. Wide public concern is raised on the contamination of antibiotics and its environmental impacts. This study investigated 3groups of antibiotics including 3 sulfanilamides, 2 quinolones, 1 tetracyclines and trimethoprim in surface waters of four typical areas in Nanchang using solid-phase extraction-high performance liquid chromatography(SPE-HPLC) focusing on the occurrence, sources and spatial distribution. The ecological risks of antibiotics were assessed on aquatic microorganisms and animals respectively. The main conclusions are summarized below.(1) The 7 selected antibiotics were detected in the four typical waters in different levels. The total concentration of 7 antibiotics in livestock and poultry breeding area water was in the rage of 0.15 to 1.57μg·L-1. Sulfonamides(SAs) are the dominating antibiotic residual in this area surface water; the total concentration of 7 antibiotics in aquaculture area ranges from 0.28 to 26.21μg·L-1. All the three groups of antibiotics have significant residual in aquaculture water; the total amount of antibiotics in urban area is between 0.21 to 13.62μg·L-1, quinolones(Qs) is preponderant residual in the urban river; only the former lake site detected small amount of antibiotics in college group at the level of 0.56μg·L-1 and no important components.(2) In the pig slurry supernatant, 6 antibiotics were detected in each sample except Ofloxacin(OFL). Sulfamethazine(SMZ) showed the highest concentration,and next is Trimethoprim(TMP). Norfloxacin(NOR) is minimum. After a period of open stack, sulfonamides and tetracyclines decreased at different levels, but quinolones had no significant decline. Sorption in the pig slurry had a big influence on the results.(3) The average antibiotic concentrations of the three group antibiotics from the four areas showes the following rules: aquaculture ponds> urban river > livestockriver> lake near universities. Domestic sewage and aquaculture were the main sources of antibiotic pollution in Nanchang surface waters. The antibiotics brought from animal feces and urine contaminations were mostly adsorbed by the surrounding soil and only small flowed into surface water through runoff ultimately.(4) The total concentration of antibiotics in the river in livestock and poultry husbandry area showed the rule of midstream>upstream>downstream. The total concentration of antibiotics in Yudai River decreased along with the river flow direction. Population density, urban sewage, industrial wastewater feedlots and aquaculture wastewater had important effects on the antibiotic pollution of Nanchang surface water. Antibiotic concentrations delined gradually because of dilution and self-purification of the rivers.(5) The potential ecological risks of the detected antibiotics were assessed via the risk quotient(RQs) method for Nanchang surface waters. In general, antibiotics in aquaculture ponds pose at least medium risk(RQs>0.1) to the relevant sensitive aquatic microorganisms. Oxytetracycline and Norfloxacin also pose medium risk(0.1<RQs<1) to daphnia and fish in these ponds. The ecological risks posed by Sulfadiazine, Sulfamethoxazole and Oxytetracycline are medium to the aquatic microorganisms in the urban river. In livestock area, only sulfadiazine poses a medium risk to S. capricornutum in duck ponds and other pose no risk. The risks in lakes near universities are not significant.