Study On Enantioselective Accumulation Of Chirai PCBs In Lotus Roots Plant

Polychlorinated biphenyls (PCBs) are a group of typical persistent organic pollutions (POPs) andthreatened the health of human because of their persistence, toxicity, and bioaccumulation. There are19PCBs displayed stable chirality at ambient temperatures out of a total of209PCBs congeners. Twoenantiomers of chiral PCBs may have different biochemical processes and toxicities, and exhibitenantioselectivities in their bioaccumulation, metabolism, biotransformation,carcinogenicity-mutagenicity-teratogenicity and the endocrine disrupting activity. Therefore, it’simportant to enantioselectively study environmental problems of chiral PCBs, and further accurately toevaluate their hazard for human health and environment ecosystem. At present there are many reportsabout enantioselectivity of chiral PCBs in the environment and animals, but few in plants. Lotus root isa kind of aquatic vegetables with bigger cultivated area and higher economic value. Some studiesshowed that lotus root would accumulate pollutants such as pesticides and heavy metals from sedimentand water, so it also may accumulate PCBs in environment. On the one hand, the accumulation of chiralPCBs in lotus root plant would restore the environment. While on the other hand, it may also lead toquality and safety problems of lotus root because of PCBs contamination. Thus, this paper used chiralgas chromatography-mass spectrometry (GC-MS) technology to study enantioselective accumulation ofchiral PCBs including PCB95,91,136,149,176and183in lotus root.Firstly, a reliable and accurate method was developed for separation and determination of six chiralPCBs in lotus root, sediment and water. Enantiomers of chiral PCBs in samples were extracted byaccelerated solvent extraction (ASE), sulphonated by sulfuric acid, purified by Florisil solid extractionphase column, separated respectively on Chirasil-Dex and BGB-172columns, and determined withGC-MS. This method was applied to the determination of some lotus root samples from the market, theresults showed that chiral PCBs were not detected in most samples, indicating lotus root is safe as forchiral PCBs.The investigations on enantioselective accumulation of chiral PCBs in lotus root were respectivelyachieved in pond and bonsai. Lotus root, stem, leaf, sediment and water were termly sampled and PCBsenantiomers in these samples were analyzed using the developed method. The results showed that theaccumulations of PCB95,91and136were enantioselective in lotus root, stem and leaf. Thereinto,enantiomers of PCB95-1, PCB91-2and (-)-PCB136were preferentially accumulated. While for PCB149,176,183, the accumulations were enantioselective. The racemic presences of six chiral PCBsindicated there are not enantioselective degradations in sediment and water. The concentration of chiralPCBs in lotus root is the highest in day60, and their total mount in lotus root is stable after day120.By comparing simulated experimental results in pond and bonsai, the enantioselective accumulationbehaviors of chiral PCBs in lotus root are consistent although the concentrations of chiral PCBs and thegrowth environment of lotus root are different. Additionally, the enantiomeric concentrations of chiralPCBs in sediment and water have not significant differences. These suggested that the enantioselectiveaccumulation of chiral PCBs in lotus root depended on the biological characteristics of lotus root itself. Because of low bio-enrichment factors, lotus root is not suitable for a model plant in phytoremediationof contaminative environment.