Bioccumulation Characteristics Of Organotins In Aquatic Animals And Organotins' Trophic Transfer In Food Web In The Three Gorges Reservoir Region

Tributyltin(TBT)and triphenyltin(TPh T)in organotins(OTs)are the only two metal compounds currently known in endocrine disruptors,which are also considered to be two of the most toxic chemical substances introduced into the water environment artificially.Due to their high toxicity and bioaccumulation,many countries and regions have restricted and supervised the use of OTs products.In 2001,the International Maritime Organization(IMO)adopted The International Convention on the Control of Harmful Anti-fouling Systems on Ships(AFS Convention)which were brought into effect officially in 2008 to prohibit ships from using OTs antifouling paints.In 2011,the AFS Convention went to effect in China.The monitoring of OTs in aquatic environment of the the Three Gorges Reservoir Region(TGRR)over the years showed that OTs pollution has existed in various waters for a long time,which may pose risks to the ecological environment,aquatic animals and even humans in the TGRR.However,the research on accumulation characteristics of OTs in wild aquatic animals in the TGRR is currently still none.This study comprehensively discussed current situation of OTs pollution in the habitat of aquatic animals in the TGRR,and the distribution and enrichment characteristics of OTs in aquatic animals ten years after the formal implementation of the AFS Convention in China.And it emphatically explored the accumulation regularity of OTs in wild fishes and transfer between trophic leves of OTs in the food web.The main content and results of the research are as follows.(1)The research on the concentration levels and distribution of OTs in the habitat of aquatic animals showed that ten years after the formal implementation of the AFS Convention in China,monobutyltin(MBT),dibutyltin(DBT),tributyltin(TBT),monophenyltin(MPh T),diphenyltin(DPh T)and triphenyltin(TPh T)were still widely detected in the water environment of the TGRR,and there still existed new input of TBT and TPh T.Among 6 kinds of OTs,TBT appeared a highest detection rate,and MBT appeared a highest concentration level.And the concentration levels of butyltins(BTs)were generally higher than those of phenyltins(Ph Ts).At the same time,it was observed that BTs levels in the lower reaches of the reservoir region was generally higher than or reached to which in the upstream,and the levels in wharf zone was significantly higher than that in non-wharf zones,indicating that the main source of TBT was the leak of antifouling paints from ships.The detection rates and concentration levels of Ph Ts were both low in water environment in the TGRR,and there were no significant spatial differences among Ph Ts levels of different sampling sites.(2)OTs,especially TBT and TPh T,were widely detected in aquatic animals in TGRR.The log BAF values of TBT and TPh T concentration levels were 3.77 and 4.37,respectively,which were exceed the biological accumulation standard(3.7),indicating that TBT and TPh T have significantly accumulated in aquatic animals in the TGRR.Even though the concentration levels of TBT in the aquatic animals were generally higher than those of TPh T,the biological accumulation factors of TPh T were higher than TBT,showing more stronger bioaccumulation.The differences in organotin concentrations and spatial distributions were not significant.The correlations between OTs and biological indicators were not obvious.The influence of feeding habit on TBT and TPh T levels was more significant than habitat layers.In aquatic animals of various feeding habit in the TGRR,the concentration levels of TPh T showed the trend of herbivores < filter feeders< omnivores < carnivores.TBT concentration levels in carnivores were significantly higher than those in other three kinds of animals.The degradation products of TBT and TPh T were not detected in most aquatic animals.The degradation index of TPh T presents trends of carnivores < omnivores < filter feeders < herbivores,and the correlation between TBT degradation index and feeding habit was not obvious.(3)This study built a micro-food web for aquatic animals in the TGRR,and the trophic levels ranged from 2 to 4.The concentration levels of TBT and TPh T significantly increased with an increase in trophic level.The trophic magnification factors(TMFs)of TBT and TPh T were 3.63 and 3.71,respectively,which both showed significant effects of trophic transference and biomagnification.And the effect of biomagnification of TPh T was stronger than TBT.MBT also showed a significant increase with trophic levels whose TMF was 2.95.The results of ecological risk assessment using chronic thresholds and different water quality standards of OTs showed that TBT and TPh T have caused significant ecological risks on aquatic animals in some areas of the TGRR.TBT and TPh T have showed rather significant trophic transference and biomagnification effect which may have caused ecological risks in a lager range.Therefore,we should pay more attention to constant monitoring of OTs in the water environment of the TGRR and take imperative measures to control OTs pollution.