Occurrence Of Non-Steroidal Anti-Inflammatory Drugs In Taihu Lake And Its Effect On The Physiological Growth Of Reed

Non-steroidal anti-inflammatory drugs（NSAIDs）are a class of drug residues that are detected more frequently in surface water.Although their residual concentration in the water environment is very low,they are only trace levels.Its active source of continuous input causes potential environmental risks to non-distorting aquatic organisms in the water environment and even affects human health through the food chain and food web.Therefore,it is necessary and important to study the occurrence of NSAIDs in the water environment and its impact on aquatic organisms.At present,NSAIDs have more researches on aquatic animals and less on aquatic plants,but under the continuous stress of NSAIDs,their effects on the physiology and growth of aquatic plants throughout the life cycle have not been reported.In addition,after the stress of aquatic plants under NSAIDs,the dynamic response of root exudates in different growth periods in the life cycle has not been reported.Therefore,this study first determined the occurrence concentration of NSAIDs in the water body of Taihu Lake in China,analyzed the temporal and spatial distribution of the NSAIDs and conducted ecological risk assessment.Then,the reeds that are widely present in China’s freshwater environment were used as test organisms.Five typical non-steroidal anti-inflammatory drugs,ibuprofen,ketoprofen,diclofenac,naproxen,and indomethacin,were exposed.The effects of NSAIDs on the components of reed root exudates throughout the life cycle were studied.Finally,reeds were also used as test organisms to study the accumulation of NSAIDs in reeds of different growth stages,oxidative stress responses of reeds of different growth stages and their physiological growth indicators.The contents and main conclusions of the study are are summarized as follows:1.The concentration of NSAIDs in the northern,western and eastern waters of Taihu Lake is relatively high,ranging from 75 to 90 ng·L-1,of which ketoprofen is the main contributor to NSAIDs compound pollution and generally accounts for more than 80%of the total concentration of NSAIDs.The concentrations of NSAIDs in Taihu Lake are higher in summer(15.9-134.3 ng·L^-1)and autumn(16.4-144.6 ng·L^-1)but lower in spring(25.3-72.5ng·L^-1)and winter(14.6-57.4 ng·L^-1),being greatly correlated with water conductivity and pH,respectively.The MRQ model evaluation reveals that there are 9 sections in Taihu Lake showing a high ecological risk（MRQ>1）of the NSAID mixtures throughout the year.The ecological risk of the NSAID mixtures at a medium or high level（MRQ>0.1）lasts for a long time spanning the spring,summer and autumn seasons in which the risk is greatest in autumn.Overall,the pollution caused by the NSAID mixtures in the water of Taihu Lake should not be ignored and especially great attention should be paid to the pollution in autumn.2.Under the NSAIDs stress,the total organic carbon（TOC）content in the root exudates of Phragmites communis significantly changed.The total organic carbon content in the root exudates of the five growth-period experimental groups was generally lower than that of the control group,and generally decreased by more than 10%compared with the control group.There were 7,4,10 and 15 monosaccharides,fatty acids,organic acids and amino acids detected in the root exudates,respectively,and their relative contents in the experimental group and the control group were significantly different.The secretion of arabinose,palmitic acid,stearic acid,quinic acid,malonic acid,oxalic acid,malic acid,citric acid,propionic acid,taurine and ornithine under NSAIDs stress increased significantly,generally increased by 15%-60%.It shows that these 11 substances are the components of Phragmites australis actively responding to NSAIDs stress.3.The cumulative concentration of NSAIDs in the reed tissues at the seedling stage and the leaf-leaving stage was low.The accumulative concentration of NSAIDs in the reed tissue increased significantly after the rapid growth period.The accumulative concentration of NSAIDs in the roots of reed was generally greater than 15 ng·g^-1,which was greater than that of the stem and leaf(<10 ng·g^-1);The reed tissue began to be affected by NSAIDs stress,resulting in oxidative stress,and the antioxidant system started.Among them,the increase in Superoxide dismutase（SOD）,ascorbate peroxidase（APX）and peroxidase（POD）activity of enzyme antioxidants was the most obvious,generally increased by 10%-40%,which has the effect of alleviating the toxicity of NSAIDs.The important role,and the SOD,APX and POD enzyme antioxidant systems regulate the secretion of specific root secretions may be one of the important detoxification pathways.Under NSAIDs stress,the amount of chlorophyll a and b in reed leaves decreased significantly,generally decreased by 20%-40%and 30%-43%respectively.However,the stress of NSAIDs has little effect on growth indicators,which is related to the detoxification mechanism of Phragmites australis,and SOD,POD and APX enzyme antioxidant system regulate secretion of specific root exudate components may be one of important detoxification path way.