Bioaccumulation Effect Of Methyl Siloxanes In Aquatic Organisims

As kinds of synthetic organic silicon compounds,methyl siloxanes include two structures:liner methyl siloxanes and cyclic methyl siloxanes(expressed as Ln and Dn,respectively,n is the number of silocon atom).Because of their unique physical and chemical properties,they are frequently used in various fields of national economy and have been detected in a variety of environmental mediums.The amount of contaminants absorbed by the organisms can generate an important effect on the risk assessment,thus this research adopted the low dose exposure concentration of environment related laboratory experiment and made the methyl siloxanes exposure concentration in water phase maintain in the scope of relatively stable during the whole uptake stage.Cyprinus carpio as a biological subject,during 32 days exposure in a tank,then transfered to clean water for keeping 32 days,after that,we determined the concentrations of methyl siloxanes in C.carpio during different expose time.By using the kinetics equation,we got the absorption rate constant and the purification rate constant of methyl siloxanes in C.carpio.Besides,we collected aquatic biological samples in Shuangtaizi Estuary and determined the concentrations of methyl siloxanes in organisms.The method of stable isotope was used to determine the trophic level of biological samples in the ecology system.Based on these,the linear relationship was established between the methyl siloxanes per body fat and trophic level to analysis the trophic magnifications of organisms in the aquatic food chain.This study showed that:(1)five siloxanes(D4,D5,D6,D7 and L10)were detectable in C.carpio.The concentrations changed over time in C.carpio obviously.At the beginning of uptake,the concentration increased fast then became more gently.In the depuration period,the concentrations declined constantly.The kinetics equation was used to obtain the absorption rate constant and purification rate constant.The bio-concentration factor(BCF)of D4 was higher than other compounds,with the value of 6197.34 L/kg.The result demonstrated that D4 was obvious bio-concentration.(2)In field study,9 kinds of methyl siloxane were detectable,including D3-D7 and L8-L10.According to the predator-prey relationships,we divided the organisms into three major food chains.In the food chain of Plankton-Scapharcasubcrenata-Glossaulax didyma-Palaemon gravieri,D5(R = 0.88,p<0.88),D6(R = 0.72,p<0.01),L7(R = 0.83,p<0.001),L8(R = 0.76,p = 0.001)were observed significantly magnification.It suggested that D5,D6,L7,L8 can be amplified in the food chain.In summary,combined with bio-concentration factor and trophic magnification factor,D4,D5,D6,L7,L8 were with effect of bioaccumulation,D4 can generate bioaccumulation effect through the organisms directly with environmental contact,while D5,D6,L7,L8 can generate bioaccumulation effect through trophic magnification in the food chain.