| Hexabromocyclododecanes?HBCDs?as a kind of hydrophobic aliphatic brominated flame retardant,are widely used in electronics,chemicals and building materials.Baiyangdian is the largest natural lake in the North China Plain and the most important functional water body in the Xiong'an New Area.In recent years,various types of POPs pollution in Baiyangdian Lake has become increasingly serious.In the present thesis,the distribution and the selective behavior of diastereoisomers and enantiomers of HBCDs in aquatic and terrestrial plant systems from Baiyangdian Lake was conducted for the first time,Main results acquired are as follows:1)The concentrations of?HBCD in Baiyangdian water,aquatic plants and sediment samples were in the range of 0.899.64 ng·L-1,N.d.?lower than the detection limit?7.26ng·g-1?dry weight?and 0.8415.93 ng·g-1,respectively.The concentrations of?HBCD in soil and terrestrial plant samples were in the range of 1.328.25 ng·g-1 and N.d.2.18ng·g-1,respectively.Compared with other areas worldwide,HBCDs concentrations in Baiyangdian Lake were at relatively low level.2)It is noticeable that significant diastereomer-and enantio-selective enrichment behavior of HBCDs were found in the lake.The average composition percentage of?-,?-,?-HBCD in water samples was 18.89%,41.25%,39.86%,respectively.?-HBCD and?-HBCD were the main diastereoisomers in most plant and sediment samples.?-?-HBCD was more readily to be selectively enriched than?+?-HBCD in water samples.The major enantiomers in aquatic plant samples were?-??-HBCD and?-??-HBCD.?+??-HBCD and?-??-HBCD were found as the dominant enrichment enantiomers in the sediment.Similar to the above media,?-HBCD and?-HBCD were the dominant diastereoisomers in soil and plant samples,with an average percentage contribution of 68.24%and 44.10%,respectively.?-?-HBCD was more readily to be selectively enriched than?+?-HBCD in most soil and plant samples.3)Root concentration factors?RCFs?of?HBCD from soil to plant root was in the range of 0.120.93,with the highest accumulation ability of Hemistepta lyrata Bunge and the lowest of Limonium sinense.Translocation factors?TFs?from root to shoot ranged from0.09 to 0.81.The plant acropetal translocation ability was in the order of Limonium Sinense>Eleusine indica Gaertn>Capsella Bursa-pastoris>Hemistepta lyrata Bunge.No significant correlations were found between RCFs and log Kow,as well as TFs and log Koww in soil-plant system,which might be resulted from both the plant species differences and the complexity of the real environment.4)In this study for the first time estimated the reserves in the surface sediments of the entire Baiyangdian Lake,and the reserve of?HBCD was 68.53kg.The results of ecological risk assessment showed that the ecological risk of HBCDs in Baiyangdian Lake water and sediment were low level,which provides priority for the zonal management of Baiyangdian.This paper for the first time provides evidences of HBCDs contamination and their stereoselectivity behavior in the plant system in Baiyangdian Lake,and it is of great significance for comprehensive assessment of its regional ecological security risk,and pollution control of persistent organic pollutants?POPs?. |
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