Residual Level And Distribution Characteristics Of Typical Antibiotics In Aquaculture

The pollution of the aquaculture environment is becoming more and more serious,resulting in the frequent occurrence of fish,shrimp and crab aquatic diseases,especially in intensive aquaculture systems.In order to increase the output of aquaculture,a large number of antibiotics are used in the aquaculture industry.The most common way of administration is to mix antibiotics and feed.Most of them are discharged into the environment in the form of raw pesticide,which results in antibiotic residues in the water and sediment of aquaculture ponds and brings various potential risks to the ecological environment.In this study,by investigating commonly used antibiotic species in different aquaculture types(fish,shrimp,crab),Sulfadiazine(SD),Sulfamerazine(SM1),Sulfamethazine(SM2),Sulfadimethoxine(SDM),Sulfamethoxazole(SMX),Trimethoprim(TMP),Norfloxacin(NOR),Ciprofloxacin(CIP),Enrofloxacin(ENR),Furazolidone(AOZ),Chlortetracycline(CTC),Oxytetracycline(OTC),Doxycycline(DOX),Amoxicillin(AMX)and Olaquindox(OLA)are 15 typical antibiotics as target antibiotics.Using solid phase extraction combined with high performance liquid chromatography tandem mass spectrometry(SPE-HPLC-MS/MS)and microwave extraction-solid phase extraction combined with high performance liquid chromatography tandem mass spectrometry(MAE-SPE-HPLC-MS/MS)technology,detection typical antibiotics in aquaculture waters and sediments,analysis of the levels and distribution characteristics of antibiotics in different culture types,seasons and substrates,and research on the environmental behavior of 4 highly polluting antibiotics in the laboratory to provide scientific basis for aquaculture antibiotic exposure risk and ecological risk assessment.The main findings are as follows:(1)HPLC-MS/MS method for trace detection of 15 typical antibiotics in aquaculture has been established.The detection limit of the instrument(LOD)is 0.003-1.23 ?g·L-1 and the quantification limit of the instrument(LOQ)is 0.01-4.10 ?g·L-1,the precision of instrument is 0.14-5.17%.SPE pretreatment and MAE-SPE pretreatment methods were established for aquaculture water and sediments respectively.The recovery rates of water and sediments are 68.7-140.8%and 69.7-109.4%The detection limits of the methods(MDL)is 1.15-6.35 ng·L-1 and 1.52-10.95 ?g·kg-1,and the precision of the method are 0.35-13.50%and 0.09-21.40%.It provides an analytical method with low detection limit and high precision for the next research on pollution characteristics and environmental behavior.(2)A variety of antibiotics have been detected in the water of aquaculture ponds,the total residues of antibiotics in aquaculture pond water ranged from 5.60-5837.52 ng·L-1 and the total residue of antibiotics in the aquaculture pond sediment was 2.84-1437.16 ?g·kg-1.The total concentration of antibiotics in the sediment was much higher than that of the upper water,indicating that antibiotics are mainly present in aquaculture sediments.From the perspective of seasonal distribution characteristics,there are many types and high levels of antibiotics detected in March and July in the water;the concentration of most antibiotics varies significantly with the seasons;the total amount of antibiotics in the sediment in September is 9.8 times that in December,the residues of fluoroquinolones decreased significantly in December,while the residues of other antibiotics did not change much.From the detection rate,SD,SDM,TMP and DOX in water were detected in 4 months,the detection rates were 65.4%,62.1%,66.2%and 45.4%;there are differences in the detection frequency and concentration of different antibiotics.The detection rate of DOX is high,but the content level is only a few ng·L-1,and the fluoroquinolones in the sediment have higher detection frequency and residual level.The detection rate was 81.0%,and the average concentration was ?g·kg-1,indicating that the distribution characteristics of antibiotics in water and sediment are different,which is related to the environmental behavior of antibiotics in water and sediment.(3)The types and concentrations of antibiotics detected in the culture ponds of different culture types are different.The types and concentrations of antibiotics detected in the water of fish culture ponds are large,mainly sulfonamides,fluoroquinolones and AMX,shrimp and crab ponds only have a higher detection amount for specific antibiotics,the detected concentrations of TMP in Macrobrachium rosenbergii ponds in September,March and July are all greater than 800 ng·L-1,the highest concentrations of OLA and AOZ detected in juvenile Eriocheir sinensis pond are 733.83 ng·L-1 and 711.81 ng·L-1,ENR and NOR have the highest concentration detected in adult Eriocheir sinensis(C1)ponds are 101.67 ng·L-1 and 388.73 ng·L-1.The use of antibiotics may differ in the same cultured species in different cultured areas.Among the pond sediments,all ponds had higher antibiotic residues in September than in December.Fish ponds had the most antibiotics detected,followed by shrimp ponds and crab ponds.Tetracycline and fluoroquinolone antibiotics have the highest detection concentration in fish culture ponds,and TMP has the highest detection concentration in Macrobrachium rosenbergii pond,which is consistent with the water body results.(4)The order of the expected partition coefficient(Ka)of antibiotics in the pond is ENR>SM1>OTC>DOX>CTC>SMX>SDM>TMP>SM2>SD.The Ka values of fluoroquinolones and tetracyclines are higher,ranging from 1881.67-719,662.72 L·kg-1 and 321.33-57,093.58 L·kg-1.In the laboratory water-sediment system,the order of the adsorption coefficient(Kd)values of each antibiotic at equilibrium is ENR>CTC>SMI and TMP,which is similar to the Ka value order of antibiotics in the actual environment,the adsorption coefficients of the four antibiotics are 2-4 orders of magnitude lower than the actual environmental calculation results.The Kd values of antibiotics in different ponds are obviously different,the physicochemical properties of the compounds and the composition of the sediment have a great influence on the adsorption.(5)The water environment degradation experiments show that CTC in water is the most degradable,SM1 and ENR are second,and TMP has strong persistence in water.In the water phase of the simulated water-sediment system,SMI,ENR,CTC and TMP all decay rapidly within 0-7 d.The degradation half-life of CTC and TMP in sediments is long,the half-life of SMI is short,and the half-life of ENR varies greatly in different sediments,the durability of antibiotics in sediments is generally higher than that in water.(6)The detection of antibiotic residues in the surface and bottom sediments after the experiment indicates that ENR and CTC are more likely to stay on the surface of the sediment,TMP partially migrates,and SM1 has the strongest mobility,this is similar to the Kd value,indicating that the adsorption of antibiotics is negatively correlated with mobility.The difference migration of antibiotics in different ponds sediment is more obvious,indicating that sediment characteristics have a greater impact on the migration of antibiotics.