Distribution Of Antibiotics In Coastal Sediments Of Southeast China

Antibiotics have been widely used for prevention and treatment of human and animal diseases,and used as animal feed additives.In recent years,as the abuse of antibiotics has become increasingly serious,it is not only possible for antibiotics to induce drug-resistant bacteria in water environment,but also to accelerate the spread of antibiotic resistance genes(ARGs)in the environment as well as in vivo.Antibiotics and ARGs are also proposed as "emerging pollutants" in the water environment research areas and are receiving wide attention.In China,the abuse of antibiotics is very serious,so it is necessary to study antibiotic residues and ARGs in water and sediment in China.This thesis selected thirteen Chinese coastal aquaculture ponds,five sites along the Huangpu River and one site at Chongming Island.Using sample extrcation and UPLC-MS/MS hyphenated techniques,to the concentrations of tetracyclines and sulfonamides antibiotics among 11 compounds in the surface sediments and deep sediments were determined.There is no uniformity of antibiotics pollution in the surface sediments of coastal aquaculture sites in China,with the main pollutant being tetracyclines accounting for 68-99%.The average concentrations of Tetracycline(TC),Oxytetracycline(OTC),Doxycycline hyclate(DXC)and Chlorotetracycline(CTC)in the surface sediments of the fish ponds were 6.45,7.40,9.34 ng/g and 0.42 ng/g,respectively.The maximum values of sulfadiazine(SD),sulfapyridine(SP),sulfamethoxazole(SMX),sulfathiazole(ST),sulfamethazine(SMT),sulfamerazine(SM)and sulfaquinoxaline(SQ)in the surface sediments of fish ponds were 0.40 ng/g,0.22 ng/g,0.35 ng/g,0.08 ng/g,0.09 ng/g,0.08 ng/g and 0.13 ng/g.On the other hand,compared with the control group,the high value of tetracycline drugs in the fish ponds,sea water may be contaminated by other point sources,which in turn will affect the fish pond water environment.The concentrations of sulfonamides in water samples of Wusongkou ranged from 1.48 to 79.44 ng/L,and the concentrations of tetracycline ranged from n.d.to 0.31 ng/L.The range of total concentrations of 11 kinds of target antibiotics in sediment samples from Wusongkou were 1.26-69.49 ng/g.The maximum concentrations of SD,SM and SP were at depths of 20 cm,40 cm and 10 cm,respectively,with the highest concentrations of 1.15 ng/g,1.06 ng/g and 4.07 ng/g.The concentration of SMX,ST,SMT and SQ at depth(10-100 cm)was less than at surface(less than 10 cm),and there is no obvious trend in the depth profile,the average concentrations of the four kinds of antibiotics in surface sediments were 0.23 ng/g,0.29 ng/g,0.02 ng/g and 0.44 ng/g.At 30 cm and 100 cm,OTC showed the concentration highest peaks,respectively 5.20 ng/g and 6.39 ng/g;CTC’s highest concentration of 25.33 ng/g showed at 30 cm;the concentration of TC and DXC in deep sediments were very low and there were no obvious trends in vertical direction.From the correlation analysis between the antibiotic concentrations and environmental factors in Wusongkou sediments,it was found that the average particle size and sediment contentration showed a significant correlation(P<0.01),followed by the water content and total organic carbon content(TOC),but the value of pH and oxidation reduction potential(Eh)the target value did not show significant correlation with the antibiotic concentrations(P>0.05).Using general PCR method,sulfanilamide and tetracycline resistance genes in sediments were detected after the discovery of sul genes distribution were widespread in 13 fish ponds sediments.The relative expression of target antibiotic resistance genes(16S rDNA)decreased as sul2>sul1>tefW>tetQ>tetO>tetM>sul3>tetA>tetB.The tetA and tetB genes were not detected.The sulfanilamide resistance genes were the main type of resistance genes in the surface sediments of the fish ponds.sul2 showed the highest relative expression which was the most important target antibiotic resistance gene in fish pond sediments in this study.The relative expression of target antibiotic resistance genes(16S rDNA)in Wusongkou sediment samples decreased as sul2>tetW=sull>tetM>tetQ>tetO =tetA = tetB = sul3.The tetO,tetA,tetB and sul3 genes were not detected.sul2 gene was the main type of resistance genes of sulfanilamide resistance genes in the Wusongkou sediments,and tetW was the main type of tetracyclines resistance genes.sull,sul2 and tetW were the only three resistance genes found in the deep sediment of Wusongkou.