Bioaccumulation And Trophic Transfer Of Antibiotics In Aquatic And Terrestrial Habitats In The Yellow River Delta

Antibiotics can inhibit the growth of bacteria or kill bacteria,and are widely used in human medical treatment,husbandry,and aquaculture.Due to the incomplete metabolism of antibiotics by human or animals and the low removal rate of antibiotics by municipal sewage treatment plants,antibiotics can be continuously discharged into the environment,which leads to its "false persistence".This can lead to continuous exposure of organisms in contaminated environments to antibiotics,which may lead to threats to human health through bioaccumulation and biomagnification.The Yellow River Delta Nature Reserve is a typical estuarine wetland ecosystem in China,which is rich in animal and plant resources.However,the aquaculture activity in the Yellow River Estuary is intense,and the antibiotics used in the breeding process may pollute the wetland system in the reserve.The boundary between water and land in wetland system is complex,and there are many species such as amphibians and reptiles that can move back and forth between water and terrestrial habitats.As a result,the independent study of aquatic or terrestrial habitats can not fully reflect the bioaccumulation and trophic transfer of antibiotics in the wetland system.In addition,different environmental conditions and biological characteristics in aquatic and terrestrial food webs may affect the bioaccumulation and trophic transfer of antibiotics.At present,the studies on bioaccumulation and trophic transfer of antibiotics are mostly focused on aquatic habitats,but there are few studies on terrestrial habitats and the comparison between them.Therefore,it is urgent to study the bioaccumulation and food chain transfer effects of antibiotics in aquatic and terrestrial habitats.In this study,19 kinds of antibiotics with high detection rate in aquaculture environment were selected as target pollutants in the Yellow River Delta Nature Reserve.Samples of eight species of fish(silver carp,crucian carp,variegated carp,carp,perch,banded catfish,pike,catfish);six species of insects(golden cicada,dragonfly,katydid,spider,grasshopper),two amphibians(frogs,toads),one crustacean(crab)and one mollusk(snail)were collected.Six plant samples(endive,oriental wormwood,wild soybean,bluish dogbane,suaeda salsa,rice)and environmental samples(water,sediment and soil).The occurrence and distribution of antibiotics in biological and environmental samples were analyzed,the biological accumulation of antibiotics in aquatic and terrestrial animals were studied,and the trophic transfer effects of antibiotics in aquatic and terrestrial food webs were investigated.The main contents and conclusions of this study are as follows:(1)The occurrence and distribution characteristics of antibiotics in multi-environmental matrix and typical plants in the Yellow River Delta Nature Reserve were investigated.The total concentrations of antibiotics in water samples,sediments and soil in the Yellow River Delta Nature Reserve were 6.56～37.15ng/L,4.40～15.80ng/g dw(dry weight)and 5.66～7.07ng/g dw,respectively.The concentration of sulfonamides was the highest,which was the main type of antibiotics,followed by fluoroquinolones,tetracyclines and macrolides.Plant-related studies have shown that sulfonamides are the dominant antibiotics in plants,the leaves and stems of rice are the most important antibiotic accumulation organs,and eating rice in the Yellow River Delta Nature Reserve does not cause human health risks.The results of spatial variation of antibiotics showed that the variation of antibiotic concentration with longitude in the east-west direction was not obvious,and no obvious pollution dilution was observed.The special hydrodynamic characteristics and the law of material diffusion and transfer in the wetland system may be the reasons.(2)The bioaccumulation ability of antibiotics in typical aquatic and terrestrial animals in the Yellow River Delta Nature Reserve and its relationship with the physicochemical properties of antibiotics were explored.The total concentration of antibiotics in aquatic organisms was 11.61～63.08 ng/g dw,and that in terrestrial organisms was 4.21～9.11 ng/g dw.About the composition of antibiotics,sulfonamides and fluoroquinolones were the most important antibiotics in organisms.The results of bioaccumulation study showed that fluoroquinolone antibiotics had the strongest bioaccumulation ability in the Yellow River Delta Nature Reserve.Ofloxacin(OFL)and erythromycin(ERY)had the strongest bioaccumulation ability in aquatic and terrestrial organisms,respectively.In addition,the physicochemical properties of antibiotics had a significant effect on the bioaccumulation ability of antibiotics.It was found that the bioaccumulation ability of antibiotics in aquatic animals was expressed by biological accumulation factor(BAF)or bio-sediment accumulation factor(BSAFa),and its logarithm value was negatively correlated with the logarithm of octanol-water partition coefficient(Kow)or pH corrected partition coefficient(Dow).The accumulation ability of antibiotics in terrestrial animals was expressed by bio-soil accumulation factor(BSAFt),and its logarithm value was positively correlated with the logarithm value of octanol-air partition coefficient(Koa)of antibiotics.The different living environment of aquatic animals and terrestrial animals may be the cause of this phenomenon,indicating that there are differences in the bioaccumulation behavior of antibiotics between aquatic and terrestrial organisms.(3)The structure of aquatic and terrestrial food webs in the Yellow River Delta Nature Reserve was clarified,and the trophic transfer of antibiotics in different food webs and their relationship with the physicochemical properties of antibiotics were explored.The relative carbon source value(RCS)of each organism was calculated by carbon and nitrogen stable isotope technique to determine that the collected organisms belong to the same ecosystem,and their trophic levels(TL)were calculated to determine the structure of the food webs.The total concentration of antibiotics studied had significant biodilution in aquatic food web(p<0.05)and significant biomagnification in terrestrial food web(p<0.05).For single antibiotics,the range of trophic magnification factor(TMF)in aquatic food web was from 0.38 of enrofloxacin(ENR)to 2.36 of roxithromycin(ROX),and from 0.77 of enrofloxacin(ENO)to 2.57 of tetracycline(TC)in terrestrial food web.The analysis of the physicochemical properties of antibiotics showed that the TMF of the total concentration of antibiotics in the aquatic food web was positively correlated with the logarithm of Dow or Koa,and the TMF in the terrestrial food web was positively correlated with the logarithm of Koa.