Occurrence,Bioaccumulation And Trophic Transfer Of Antibiotics In The Beibu Gulf,South China Sea

Antibiotic is a group of medicine with antibacterial activity,which have been widely applied in human medicine,aquaculture and husbandry.China is the largest producer and consumer of antibiotics all over the word based on the market data.A large amount of antibiotic that have been released in the environment would present a pseudo-persistent pollution,and ultimately cause potential harm to human health and the ecosystem.Nowadays,most reported investigations mainly focused on the pollution of antibiotics in fresh water,while the occurrence and fate of antibiotics in the marine environment have not well understood.Therefore,the objective of this study was to evaluate the occurrence,bioaccumulation pattern and trophic transfer in the Beibu Gulf,South China.The main research results are as follows:(1)A robust and sensitive analytical method is established for simultaneous extraction and instrumental analysis of 22 antibiotics in various environmental media.The recoveries for the target compound in water,sediment and biota samples were in the range of 64–137%?61–164%and 70–168%,respectively.The limit of detection for the analytes in water,sediment and biota samples were in the range of 0.01-0.18 ng/L?0.01-0.09 ng/g dry weight(dw)and 0.04-0.24ng/g wet weight(ww),respectively.(2)The results showed that 19,18 and 20 antibiotics were detected in seawater,sediment and biotia samples in the Beibu Gulf.The total concentrations of antibiotics in water,sediment and in biota samples ranged from 1.74-23.83ng/L,1.33-8.55 ng/g(dw)and 0.68-4.75 ng/g(ww),respectively.Sulfamethoxazole(SMX),trimethoprim(TMP)and norfloxacin(NOX)were predominant in seawater,while NOX and enoxacin(ENX)were the most abundant antibiotics in sediment.ENX,NOX and ofloxacin(OFX)were the main antibiotics in biotia samples.Spatially,a decreasing trend of antibiotic levels from coast/nearshore to offshore was observed,with relatively high levels being observed at the sites close to the Qinzhou Bay and Qiongzhou Strait.The total concentrations of target antibiotics in examined marine taxa descended in the order:crustacean>cephalopod>fish.(3)The sediment-water partitioning coefficients(K_d)were positively correlated with log molecular weight(MW)for most antibiotics.Livestock activities and aquaculture were identified as significant antibiotic sources in the Beibu Gulf based on the principal component analysis with multiple linear regression(PCA-MLR)and Unmix model.Risk assessment revealed that SMX and ciprofloxacin could pose medium risks to algae in the Beibu Gulf.Log BAFs(bioaccumulation factor)for antibiotics in all organisms ranged from-0.50 for erythromycin-H₂O(ETM-H₂O)to 2.82 for sulfamonomethoxine(SMM).Significantly negative correlation was observed between the log D_ow and log BAF values.The trophic magnification factors(TMFs)for sulfadiazine(SDZ)and ENX were greater than unity,suggesting the trophic magnification of these chemicals through the food web.In contrast,ENR,ciprofloxacin(CIX),OFX,NOX,ETM-H₂O and TMP were biodiluted in the food web from the Beibu Gulf.