Spatial-temporal Distribution And Risk Evaluation Of Four Typical Antibiotics In River Networks Of Taihu Lake Basin

The problem of water environment pollution caused by the unreasonable and irregular use of antibiotics has received increasing attention.As an important antibiotic production and usage nation,the "pseudo-persistent" and high ecological risk of antibiotics will lead our country to face serious antibiotic pollution problems.Therefore,building the risk assessment method and analyzing the potential risk of aquatic environment may be beneficial to ensure the safety of water supply and reduce the adverse impact of water pollution incidents.With the increasing concentration level of antibiotics in the aquatic environment,the potential threat to ecosystem and human health in aquatic environment has received wide concern.Great research progress have been achieved by some researchers,such as temporal and spatial distributions,traceability sources,risk assessment and so on.The Lake Taihu basin with dense population which is the economic developed areas in China is featured by complex plain river networks and proliferates intensive animal husbandry and aquaculture.A large number of human and veterinary antibiotics dissolved into the river water inflow the Lake Taihu,which has seriously threatened the safety of Taihu Lake water quality safety and the health of water ecosystem in the drinking sources areas of rivers and lakes.However,the occurrence status,potential sources and risks of antibiotics in the complex river Taihu Lake Basin are still unclear.In this study,the complex river networks in the upstream Taihu Lake was chosen as study area.And four typical antibiotics of Tetracycline,Sulfonamide,Fluoroquinolones and Macrolide were monitored under different water conditions.The temporal and spatial distributions and potential source of four typical antibiotics Sulfamethoxazole(SMX),Ofloxacin(OFL),Roxithromycin(ROM),and Oxytetracycline(OTC),in aqueous and sedimentary phases of the river networks of Taihu Lake Basin were investigated.The human health and ecological risks were evaluated using quotient method for these four antibiotics,which provided an important scientific basis to effectively control the ecological risk and aquatic ecological health of antibiotics in the complex river networks in the Taihu Lake Basin.The main conclusions of this article include:(1)Results showed that the detection rates of OTC,ROM,OFL,and SMX in aqueous phases of the Taihu Lake Basin were 96.5%,57.0%,60.5%,and 4.5%,respectively.The detection rates of OTC,ROM,OFL,and SMX in sedimentary phases of the basin were 96.5%,95.5%,90.0%,and 44.5%,respectively.OTC had the highest concentration of 17.85 ng/L in aqueous phase,while SMX had the highest concentration of 46.74 ng/g in sedimentary phase.The detection rate and concentration of OTC in aqueous and sedimentary phases were higher than that of the other three antibiotics.(2)Obviously,the concentrations and detection rates of the four typical antibiotics SMX,OFL,ROM,and OTC in the river networks of Taihu Lake Basin were higher in wet season than dry season and the distribution presented an obvious spatial-temporal variability.The complex river networks in the Taihu Lake basin mainly includes the Nanhe river and the upstream of the Yangtze river.The concentration of antibiotics in the Nanhe river is higher in flood period but lower in dry period in comparison with that of in the upstream of the Yangtze river.The antibiotic concentration decreased gradually along the flow direction in sedimentary phases.The enrichment of antibiotics due to sediment accumulation was detected in all inlets of the Taihu Lake.The spatial distribution of the antibiotics was due to the aquaculture in this area.(3)Quotient method was took from European Union to estimate the predicted noeffect concentration of antibiotics and calculate the Health Quotients.The results suggest an acceptable human health risk(HQs<0.01)of the four antibiotics in Taihu Lake Basin by the way of drinking and eating fish.The calculated value of Health Quotients was from 10-5to 10-10.The AQUATOX model and quotient method recommended from the U.S Environmental Protection Agency were used to evaluate the ecological risk of the river networks of Taihu Lake Basin.The results suggest an low ecological risk(RQs<0.1)of the four antibiotics in Taihu Lake Basin,while the ecological risk of OTC is relatively higher(RQs=0.086).The Risk Quotients of the four typical antibiotics in the river networks of Taihu Lake Basin were higher in wet season than dry season.