Transformation Of Antibiotics In The Zaohe And Weihe River Intersection Hyporheic Zone

The interaction zone between surface water and groundwater is an important interface connecting rivers and groundwater systems.As a new type of pollutant,antibiotics can selectively damage or affect the functions of other organisms.They are using reclaimed water as a carrier to migrate underground through rivers through interactive belts,thereby polluting the interaction zone and even the groundwater environment.Therefore,The interception mechanism is important for assessing groundwater environmental risks and ensuring groundwater quality,drinking water safety and human health.This study takes the Zaohe and Weihe River Intersection interaction zone as the research area,and selects three representative antibiotics,oxytetracycline(tetracycline),sulfamethoxazole(sulfonamide)and norfloxacin(fluoroquinolone).Two stages of in-situ geochemical characteristics monitoring were carried out.Through indoor experiments and model simulations,the distribution of antibiotics in interaction with the environmental factors and the behavioral characteristics of antibiotic abiotic attenuation(adsorption and hydrolysis)were carried out.The interactive simulation of the dynamic degradation characteristics of antibiotics with antibiotics and the interaction of antibiotic migration and migration resulted in the following main conclusions:1.The distribution characteristics of interaction with antibiotics and the relationship with environmental factors:The detection concentration and frequency of the three antibiotics are OTC>NOR>SMZ.The concentration of OTC is significantly higher than NOR.In the direction of the river,the concentration of three antibiotics on the Weihe River is significantly lower than that of the Zaohe River.After the Zaohe River merged into the Weihe River,the concentration of three antibiotics in surface water and groundwater showed a downward trend.In the direction perpendicular to the flow of water to the river bank,in the lateral interaction zone groundwater,the OTC and NOR are in a trend that gradually decreases with the distance from the river bank.In the longitudinally downward deposits,the three antibiotics generally decrease with depth,while the elevation of individual points is related to the cross-sectional clay structure.2.The abiotic decay of antibiotics showed that:Adsorption experiments of antibiotics on sediments showed that the adsorption capacity of the three antibiotics was SMZ>OTC>NOR,and the maximum adsorption amounts were 904.276,334.958 and 115.058 mg/kg,respectively.Hydrolysis experiments showed that the hydrolysis rates of the three antibiotics were OTC>NOR>SMZ,the half-life of OTC was 5.97~141 days;the half-life of NOR was 15.1~20.9 days,and the half-life of SMZ was 16.5~41.7 days.The rate of hydrolysis under alkaline and neutral conditions is significantly greater than under acidic conditions,and high temperatures favor the hydrolysis of the three antibiotics.The Arrhenius coefficient settlement results showed that in the aerobic environment of surface water,due to the participation of dissolved oxygen,the activation energy required for the hydrolysis reaction of antibiotics is significantly reduced,and the hydrolysis reaction is easier to carry out.Sediments and clays not only have the property of adsorbing antibiotics,but also increase the rate of hydrolysis reaction.It may be that minerals such as aluminosilicate promote the hydrolysis of antibiotics.3.Dynamic degradation experiments of antibiotics showed that:The adsorption performance of sediment on SMZ and OTC is the main factor for the interaction of antibiotics in the interaction zone under anaerobic or aerobic conditions.Under anaerobic conditions,the degradation rate of oxytetracycline was significantly higher than that of sulfamethoxazole,while under aerobic conditions,the degradation rate of sulfamethoxazole was faster.The longer the residence time,the more favorable the degradation of antibiotics in the interaction zone.However,when the residence time is small to a certain extent,the adsorption of antibiotics on the medium is significantly reduced due to the increased shear force of the water flow.The change of dissolved oxygen caused by hydrodynamic interaction conditions is more conducive to the degradation of sulfamethoxazole.Analysis of sediment microbial community structure in the interactive flow experiment,a total of 28 bacteria,67 classes,114 orders,168 families,239 genera were detected.Of all the samples,the main dominant flora consisted of 9 species,including Proteobacteria,Firmicutes,Actinobacteria,Bacteroidetes,and Chloroflexi,Acidobacteria,Planctomycetes,Gemmatimonadetes,and Verrucomicrobia.4.Interaction model with antibiotic migration and transformation showed that:Based on the indoor simulation experiment,the microbial degradation rate of two antibiotics was solved by hydrus-1d model.A model of migration and transformation of two antibiotics by heterogeneous interaction bands was simulated.The model results show that when the local surface water is replenished to the groundwater through the interaction zone,the pollutants transport faster,and the two antibiotics can basically penetrate the entire interaction zone at 120 d.