Pollution Characteristics Of Antibiotics And Antibiotic Resistance Genes In The Coastal Area Of Bohai Bay

Being one of the emerging environmental contaminants,antibiotic resistance genes(ARGs)resulting from the overuse and abuse of antibiotics pose potential threats to human health.However,little attention has been paid to the combined pollution characteristics of intracellular ARGs(iARGs)and extracellular ARGs(eARGs)in coastal areas,which are closely linked with anthropogenic activities.In this context,we collected water and sediment samples from the coastal areas of the Bohai Bay in China,performed quantitative real-time PCR and liquid chromatograph-mass techniques and analyzed the spatial distribution and seasonal variation of the ARGs and the corresponding antibiotics.The factors affecting ARGs were analyzed by correlation analysis and multivariate linear regression model.The environmental risks of antibiotics were assessed and analyzed based on the risk quotient method.The main results are as follows:Overall,iARGs and eARGs were ubiquitous in the coastal environment,and the average relative abundance of ARGs in the coastal environment was in the following order: estuary > area near the mariculture > area near the Caofeidian Industry > area rarely influenced by human activities.The class 1 integron gene(int1)and sul1 from the intracellular DNA were significantly correlated in the water and sediments.Moreover,significant correlation between int1 and sul2 from the extracellular DNA was also found in the sediments.The combination of sulfamerazine and tetracycline as well as the combination of sulfamethazine and dissolved oxygen can both explain the abundance of ARGs,implying the combined effects of multiple stresses on ARGs.Antibiotics had higher concentrations in winter than those in summer,and the concentrations were significantly higher in the sediments than in the water.There were the identical risk profiles that fluoroquinolone antibiotics and tetracycline antibiotics caused comparably high risks for both the antibiotic resistance and eco-toxicity.Additionally,fluoroquinolone antibiotics exhibited the highest ecological risk to the aquatic organisms in spite of the low concentrations,reflecting even little antibiotic residues can lead to the serious environmental risk in coastal environment.