Research On Risk Assessment,Pollution Behavior And Control Of Fluoroquinolone Antibiotics In Contaminated Sites

As the broad spectrum antimicrobial agent,the quinolones are widely used in animal husbandry.When applied to animals,60-90% of antibiotics will be excreted in the form of the original drug or metabolites by animal excretion,contaminated soil,surface water,groundwater,affected the normal life activities of plants,animals and microorganisms,and ultimately affected human health through the food chain.The antibiotic resistance gene is also a new environmental pollutant,the risk of contamination is higher than the antibiotic itself.In order to provide scientific basis for controlling the contamination of antibiotics and resistance genes,the risk assessment of antibiotics and their resistance genes was carried out by investigating the pollution of fluoroquinolones in contaminated sites,analyzing the pollution pathways and controlling the pollution.Therefore,it is of great significance to study the ecological risk,pollution behavior and control technology of quinolones in the environment.It showed that:(1)The PNEC of norfloxacin,ciprofloxacin and enrofloxacin were 2.66 ?g/L,9.92 ?g/L and5.11 ?g/L,respectively in aquatic ecosystem which were obtained by species sensitivity evaluation(SSD)method.The RQ = PEC/PNEC was used to evaluate the risk of fluoroquinolone antibiotic contamination in China.The results showed that there was no risk of contamination of fluoroquinolones in the surface water except for the low risk of norfloxacin in the surface water of the Yellow River,Bohai Bay and Daliao River.The CMC of surface water was 5.39 ?g / L for ?(norfloxacin),20.10 ?g/L for ?(ciprofloxacin),and 11.26 ?g/L for ?(enrofloxacin),and CCC was2.66?g/L for ?(norfloxacin),9.92?g/L for ?(ciprofloxacin)and 5.51 ?g/L for ?(enrofloxacin).To provide reference for establishment of antibiotic surface water standard.(2)The PNEC of norfloxacin,ciprofloxacin and enrofloxacin were 11.30 ?g/kg,1.13 ?g/kg and 45.00 ?g/kg respectively in soil ecosystem.The risk entropy method(RQ = PEC/PNEC)was used to evaluate the soils in Shandong vegetable plot,Dongguan vegetable plot and Fujian farmland,and ciprofloxacin showed high risk and should be monitored.Shandong vegetable land,Dongguan vegetable norfloxacin for medium risk,enrofloxacin for low risk.(3)In this paper,the risk evaluation system of resistance gene was established in consideration of the production process,transmission pathways,gene degradation and the resistance of resistant bacteria.Put forward the theory of “Gradient-Accumulation-Mutation”.The comprehensive risk was divided into four indices: resistance index,transmission index,pollution index and degradation index.The risk was graded and the relative risk level was obtained by scoring each index separately.(4)The adsorption kinetics of norfloxacin,ciprofloxacin and enrofloxacin in the three sites were in accordance with the quasi-second-order kinetics equation,in which the adsorption rate of three fluoroquinolones was faster under the influence of organic fertilizer.The same concentration of norfloxacin,ciprofloxacin,enrofloxacin,which ciprofloxacin more easily adsorbed,which also explains the three fluoroquinolones antibiotic migration ability CIP<NOR<ENR.The adsorption thermodynamics of norfloxacin,ciprofloxacin and enrofloxacin in three kinds of sites were in accordance with the Freundlich model and belong to the physical adsorption process.The adsorption behavior of the three media was different.Norfloxacin,ciprofloxacin and enrofloxacin Kf values in soil were: 47.4679,47.2607,33.9860,respectively;Kf values in soil + feces 81.4329,90.1779,46.2594,respectively;Kf values in soil + organic fertilizer 128.0855,133.5365,64.0914,respectively.(5)The leaching experiments of soil column showed that there was no obvious leaching of antibiotics in the soil column during the 40-day test period,and the three initial concentrations of the contaminated solution had no effect on the leaching of antibiotics in the soil column.Three different fluoroquinolones in the leaching behavior were similar.Through the literature review and the analysis of the experimental results,the reasons are as follows: norfloxacin,ciprofloxacin,enrofloxacin adsorption coefficient,soil viscosity,part of the antibiotics by soil adsorption,three antibiotics short half-life,part of their own degradation,due to the presence of soil microorganisms,do not rule out the possibility of microbial degradation.After the soil column experiment,the concentration of antibiotics in the soil column was analyzed.The results showed that the accumulation of antibiotics in the soil.Indicating that when the antibiotic untreated directly discharged into the soil,in a short time will be accumulated in the soil,due to the hydrolysis of antibiotics,difficult to contaminate groundwater.However,exposure to low doses for a long time leads to the generation of resistant genes in the soil and the formation of resistant bacteria.When the resistant genes are spread by horizontal diffusion,the generation of super bacteria is induced.Therefore,the need to prevent antibiotics into the soil environment.(6)The results showed that the activated carbon was the best,and the removal rate of norfloxacin,ciprofloxacin and enrofloxacin was more than 90%,and the removal effect was good.The adsorption of three fluoroquinolones on activated carbon was in accordance with the pseudo-second-order adsorption kinetics.The reaction time was about 60 mins,and the three fluoroquinolones reached the adsorption equilibrium.The adsorption equilibrium of activated carbon to enrofloxacin was the highest,which reached 2000 mg/kg.The adsorption of three fluoroquinolones on activated carbon accorded with the Freundlich adsorption model,which belonged to physical adsorption process.The Kf values were 1148.9735 of norfloxacin,1115.8351 of ciprofloxacin and 1200.3835 of enrofloxacin.Through the regeneration experiments,when the time was 25 mins,the regeneration efficiency reached the maximum,68.5% of norfloxacin,68.0%of ciprofloxacin and 69.9% of enrofloxacin;when the temperature was 35 ?,the regeneration efficiency of activated carbon was the highest,73.1% for norfloxacin,72.7% for ciprofloxacin and73.6% for enrofloxacin;when the frequency of ultrasonic was 40 KHz,the regeneration efficiency of activated carbon was the highest,76.5% of norfloxacin,75.4% of ciprofloxacin,and 79.0% of enrofloxacin.