Contamination Of Antibiotics In Typical Emission Sources And A River In Guangzhou

Antibiotics are extensively used in humans and animals for precaution and treatment of microbial infections due to their high efficiency,convenience and cheapness,and also frequently used as food additive to promote growth of livestock animals.After intake of an antibiotic,a significant fraction is excreted in its parent or metabolite form along with urine and feces and then enters the aquatic and terrestrial environment through multiple pathways,which will act on environmental organisms and pose a negative effect on human health and the ecosystem.To date,lots of studies have been done on the contamination characteristics and fate of antibiotics in the environment.However,the antibiotics concerned were limited and few studies have been conducted in regard to contamination characteristics and removal efficiencies of the major sources of antibiotics in the environment,as well as on overall research of an urban region.Hence,this survey was conducted to evaluate the contamination characteristics and removal efficiencies in wastewater of various classes of typical emission sources in downtown Guangzhou,as well as the contamination characteristics and ecological risks in Guangzhou section of the Pearl River,of 41 commonly used human and veterinary antibiotics.Antibiotics were identified and quantified using rapid resolution liquid chromatography tandem mass spectrometry?RRLC-MS/MS?combined with solid-phase extraction?SPE?for pretreatment.The content of this research describes as follow.?1?A sampling campaign in 5 classes of emission sources?municipal wastewater treatment plant?WWTP?,pharmaceutical factory,hospital,landfill and livestock farm?in downtown Guangzhou was carried out to assess the occurrence and removal rates of antibiotics.The results showed that 24,14,15,12 and 13 antibiotics were detected in WWTPs,pharmaceutical factories,hospitals,landfills and livestock farms,respectively,and the highest detected concentration of single antibiotic was 917 ng·L^-1?oxytetracycline in WWTPs?,127?g·L^-1?roxithromycin in pharmaceutical factories?,11.8?g·L^-1?roxithromycin in hospitals?,3.61?g·L^-1?anhydro-erythromycin in landfills?and 664?g·L^-1?oxytetracycline in livestock farms?.Antibiotics were well removed in landfills and livestock farms with the total removal rate of 99.7%and 99.5%,and limitedly removed in WWTPs,pharmaceutical factories and hospitals with the total removal rate of 49.3%,63.0%and 26.9%,respectively.The mass load and emission per capita of total antibiotics discharged into the environment in aquatic phase were 1.21kg·d^-1 and 89.3?g·inhabitant^-1·d^-1 in downtown Guangzhou,respectively.Antibiotics imcompletely removed in wastewater from typical emission sources constituted one of significant sources of antibiotic contamination in the aquatic environment.?2?Two sampling campaigns concerning antibiotics in river water in 13 sites of Guangzhou section of the Pearl River were carried out in both dry season and wet season.The results showed that 18 and 20 antibiotics were detected in water samples from Guangzhou section of the Pearl River during dry season and wet season,respectively,with a concentration range of n.d.⁶52 ng·L^-1 and n.d.⁷79 ng·L^-1.The single antibiotics detected with the highest concentration were anhydro-erythromycin and ofloxacin,respectively.The seasonal variation of various antibiotics in river water was different.Relatively higher concentrations of total antibiotics were measured in urban waterways and urban center reaches of the river,corresponding to the distribution of population density in downtown Guangzhou,indicating a relatively larger consumption of antibiotics in densely populated areas and possibly antibiotic misuse.Concentrations of total antibiotics in a few densely populated areas were close to or higher than those in influent of WWTPs,implying intensive discharge of antibiotics or even direct discharge without being treated.For the concentrations of macrolides,a distribution was observed in the order:anhydro-erythromycin>roxithromycin>clarithromycin,which may be attributed to the price factor of pharmaceuticals.?3?Two sampling campaigns concerning antibiotics in river sediment in 13 sites of Guangzhou section of the Pearl River were carried out in both dry season and wet season.The results showed that 24 and 23 antibiotics were detected in river sediments in Guangzhou section of the Pearl River during dry season and wet season,with a concentration range of n.d.⁵4800 ng·g^-1 and n.d.³430 ng·g^-1,respectively,and the most predominant antibiotic was oxytetracycline in both two seasons.The seasonal variation of various antibiotics in river sediment was different,and the concentrations of total antibiotics in dry season was overall higher than those in wet season.An overall spatial distribution was observed for concentrations of antibiotics in river sediment in the order:urban waterway in densely populated areas>river reach in densely populated areas>middle and lower reach>upper reach,as same as the occurrence of antibiotics in river water on the whole.?4?12 antibiotics were selected from detected compounds to assess the potential ecological risks in river water of Guangzhou section of the Pearl River using the risk quotients?RQs?approach.The results showed that anhydro-erythromycin had the highest RQ among all selected antibiotics with the maximum of 6.33,followed by roxithromycin and ofloxacin.The total RQs of 12 antibiotics were overall high with the maximum up to 10.1,and the total RQs of a majority of sampling sites were in a high level,indicating that antibiotics posed relatively high ecological risks in the surface water environment in Guangzhou section of the Pearl River.