Residual Characteristics And Potential Risks Of Neonicotinoids In Waters

In this dissertation,seven widely neonicotinoid insecticides?Neonics?used in recent years are selected as the target chemicals.The UPLC-MS/MS was employed to determine seven kinds of Neonics in samples from Hangzhou tap water system,Xiangshan Bay seawater samples during 2017-2019,and Xiangshan Bay and Shipu Bay seawater and sediment samples.The relative potency factor?RPF?method was used to integrate the residue of seven Neonics in these environmental medias.On this basis,the removal effect of Neonics by the Hangzhou Water treatment plants?WTP?and the potential risks of Neonics via drinking for human were evalutaed.The residual characteristics and variation of Neonics in seawater samples from Xiangshan Bay in past three years were investigated.The species sensitivity distribution?SSD?method and interspecies correlation estimation?ICE?were used to estimate the risk thresholds of representative aquatic organisms and Chinese aquatic organisms.Finally,the distribution of Neonics in the seawater and sediment of Xiangshan Bay was evaluated by the distribution coefficient(K_b/p)method.The results were described as follows:?1?The fate of Neonics in tap water system and their potential health risks in Hangzhou:Neonics were detected at all stages in Hangzhou tap water system,with the highest detection rate for Imidacloprid?87%?,followed by acetamiprid?83%?and clothianidin?54%?.At least one Neonics was detected in 85%of the samples.Thiacloprid was not detected in all samples.The highest average residual concentration in tap water samples was acetamiprid?5.8 ng/L?,followed by imidacloprid?4.0 ng/L?and nitenpyram?2.5 ng/L?.The average integrated concentration(IMI_RPF)in tap water samples was 17.2 ng/L,and the maximum integrated concentration was 105.4 ng/L.Comparing the changes of Neonics in before-WPT and after-WPT,the results show that the water treatment process will remove more than 50%of these pesticides.The maximum chronic daily intake?CDI?of Neonics for adults and children exposed to drinking water is 10.2 and 12.4 ng/kg/d.Compared to dietary intake of fruits and vegetables,drinking water exposure is only a small percentage.The integrated concentration of Neonics exposed to drinking water was less than the daily reference dose?Rf D?and the acceptable daily intake?ADI?,which were all within acceptable ranges.?2?Residual characteristics,trends and potential ecological risks of Neonics in Xiangshan Bay:95%of seawater samples from Xiangshan Bay were detected at least one Neonics.56%samples were detected more than four Neonics.The highest frequency of detection of Neonics were observed by imidacloprid?83%?following by dinotefuran?82%?.The concentrations of these two chemicals were ranged from ND to 635.77 ng/L and ND to 568.7 ng/L,respectibrly.Our resluts showed residues of Neonics were increase from 2017 to 2019,and new types of such pesticides in the region are gradually replacing the old types of pesticides for agriculture.Through SSD analysis,the exposure by the average IMI_RPF was found to pose an acute toxicity risk to approximately 10%of aquatic organisms and a chronic toxicity risk to 25%of aquatic organisms.?3?Residual levels and distribution of Neonics in the sediments of Xiangshan Bay and Shipu Bay:Neonics were frequently detected in the sediments of Xiangshan Bay and Shipu Bay.100%of the samples can detect at least three Neonics.The detection rates of imidacloprid and furfuran in the sediment and seawater samples were 100%,and the average concentrations in the seawater samples were 23.93 ng/L and 126.60 ng/L,and the average concentrations in the sediment samples were 6.66ng/g and 19.78 ng/g.The distribution ratio(K_b/p)reavled that residual of Neonics in sediment samples was higher than that in seawater samples,and Neonics are migrated from seawater samples and enriched in sediment samples.