Environmental Fate And Oxidative Degradation Mechanism Of Typical Drugs In The Yangtze River Delta Integration Demonstration Zone

In this study,50 surface water and sediment samples from 25 sampling sites in the Qingpu District,in the Yangtze River Delta integration demonstration zone were collected,and 22 typical pharmaceuticals in the samples were analyzed by high performance liquid chromatography tandem mass spectrometry(HPLC/MS-MS).The distribution characteristics,sources,and influencing factors of target drugs in the study area were analyzed in detail.Then,a Level IV multi-media fugacity model was used to simulate the environmental fate and migration of 10 typical antibiotics in the air,water,soil,and sediments in the study area from 2013 to 2019.Based on the Monte Carlo method,the evaluation conducted a risk assessment of target drugs in the study area environment,screened out potential high-risk drug compounds sulfamethazine(SMZ),and used activated biochar(ABC)/peracetic acid(PAA)-based advanced oxidation system to degrade the target drug.The degradation efficiency and activation mechanism of the ABC/PAA system on SMZ was explored,and the effects of common anions and humic acid in water on the oxidative degradation efficiency of ABC/PAA were investigated.The results showed that:(1)A total of 19 pharmaceuticals were detected in the surface water and sediments of 25 sampling points in Qingpu District,with the total concentrations ranging from0.06 to 178.67 ng·L-1 and 0.07 to 37.68 ng·g-1,respectively.Principal component analysis showed that the main sources of pollution were the discharge of veterinary antibiotics in aquaculture and domestic sewage.There was a significant correlation between lg K_oc and lg K_d(P<0.05),indicating that organic carbon in sediments played an important role in the distribution of target pharmaceuticals in water and sediments.The health risk quotient(HQ)of people of all ages exposed through the drinking route is less than 1,and the fungicide(TCC and TCS)presents a higher health risk value.(2)The fugacity model of the Level IV model could well simulate the fate and migration of 10 typical antibiotics in a multi-media environment in the Qingpu area.The results of trans-media migration and transformation flux analysis showed that advection was the main migration path of antibiotics in water;the main migration path of antibiotics in sediments was water-sediment descending and degradation.Sensitivity analysis showed that the antibiotic source discharge properties,degradation rate,and octanol-water partition coefficient(K_oc)are the most influential to model results output.Monte Carlo-based ecological risk assessment indicated that oxytetracycline(OTC),penicillin(PEN),and enrofloxacin(EFX)might pose a medium risk to the aquatic environment,and the potential ecological risks of antibiotics in water are tetracyclines>?-lactams>fluoroquinolones>macrolides>sulfonamides.(3)Activated biochar material(ABC)can effectively activate peracetic acid(PAA)to degrade antibiotic drug sulfamethazine(SMZ),and the degradation reaction process follows pseudo-second-order kinetics(R²>0.99).Electron paramagnetic resonance(EPR)and radical quenching experiments proved that both non-radicals(singlet oxygen)and free radicals(alkoxy radicals,hydroxyl radicals)existed in the ABC/PAA system,and the degradation of SMZ was dominated by singlet oxygen.Humic acid(HA),SO₄^2-and HCO₃^-slightly inhibited the degradation efficiency of SMZ in the ABC/PAA process,while the presence of Cl^-and Br^-promote the degradation of SMZ in this system.Based on oxidation product identification by ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometer(UPLC-QTOF),the cleavage of S-N,S-C bond,and smile rearrangement were the main oxidation process of SMZ in the system.The toxicity prediction results based on the ECOSAR model showed that the acute toxicity of most by-products was significantly reduced.