Transport Modeling And Risk Assessment Of Tetracycline Antibiotics In Meijiang River Watershed

As the usage of pharmaceutical and personal care products(PPCPs)increases around the world,the problems about these pollutants are becoming more serious.Among them,antibiotics have received worldwide attention from environmental scientists,toxicologists and pidemiologists because of their serious potential threat to human and ecosystem.China is the largest antibiotic production and use country in the world because of the rapid economic development and population growth.Therefore,it is imperative to carry out research on antibiotics.In this paper,we focused on four kinds of tetracycline antibiotics(TCs)widely used in livestock and poultry breeding industry.The Meijiang River watershed in Jiangxi Province with intensively livestock and poultry breeding were selected to study the transport of TCs.The partition of TCs among overlying water,suspended sediment and sediment were investigated through field monitoring and experimental analysis.The transport process and the spatiotemporal distribution of TCs in Meijiang River watershed was simulated with the SWAT model.The highest concentration of antibiotics in the environment was derived and ecological risk assessment was conducted after selection of sensitive species.The main conclusions of this study include:(1)The order of the detection rate of TCs in the three phases is suspended sediment phase > water phase > sediment phase.The concentration of TCs in suspended sediment were not different at different water regimes,the concentration of TCs in water phase and sediment phase in wet season were higher than those in dry season.In this study,the detection rate of oxytetracycline(OTC)was 100%,and the OTC concentrations in three phases were higher than tetracycline(TC),Chlortetracycline(CTC),and doxycycline DXC.The concentration of TCs in water and sediment in this study was lower than the results of other watershed,which was related to the use amount of TCs.The detection rate and detected concentration of TCs in sediment are relatively low.This might be resulted from that large proportion of sand and their low sorption capacity of TCs in sediment of the Meijiang River watershed.The contribution of TCs in particulate form to the total TCs in river water was over 50%.(2)The antibiotic transport model of Meijiang River watershed was developed by SWAT model.The model was calibrated and validated with measured data in the field.The results show that the model has high applicability.On this basis,the spatial and temporal variations of antibiotic concentration in river water are analyzed,and the upstream of the basin is the key area for antibiotic pollution.The results were consistent with the result of measured TCs in tributaries and main river along the Meijiang River.When the concentration of antibiotics reaches the peak,it is winter.This conclusion can be used as a reference value for local departments to strengthen antibiotic management.(3)The results of ecological risk assessment showed that all the TCs showed low risk to sensitive species.The risks of antibiotics to aquatic organisms follows the order of algae > daphnia > fish.Among them,the environmental prediction concentration of CTC is not the highest,but the risk to algae is the highest in this study.This is due to the lower predicted no-effect concentration(PNEC)of algae to CTC.Considering the antibiotic degradation products have higher toxicity than the parent compounds.The results of united ecological risk assessment showed that all the TCs showed low risk to sensitive species,attention should be paid to the potential risks of long-term low-dosage exposure.