Relationship Between Organic Matter From Different Sources And Bioaccumulation And Sedimentation Of Typical Persistent Organic Pollutants In Lakes And Reservoirs

In recent years,investigators show increasing interest on the interaction between algae and various pollutants in the field of aquatic pollution.As phytoplanktons contribute the primary productivity in aquatic ecosystem,they play a role on the migration and transformation of pollutants,which has been defined as a"biological pump"effect.Polybrominated diphenyl ethers?PBDEs?can be enriched and amplified in the food web of aquatic environment,which will bring about the biological risks and even human health risks.Therefore,it is necessary to carry out the migration,transformation,and sedimentation of PBDEs in the complex aquatic environment.It is also significant to investigate the"biological pump"effect of algal organic matter on sedimentation process of PBDEs,which will contribute to a more scientific assessment of the contamination of PBDEs in aquatic environment.This dissertation mainly focused on the distribution,migration,and sedimenttation of PBDEs in algae,zooplankton,suspended particulated materials?T-SPM?and sediment cores.Algae,zooplankton,and T-SPM were collected from Lianan reservoir?LA?and Liuhuahu lake?LHH?in Guangzhou,and several sediment cores were collected in several lakes and reservoirs from Southern China,Southwest China,and Northeast China,respectively.Gas chromatography and mass spectroscopy?GC-MS?were used to analyze the contents of PBDEs in the collected samples.Rock Eval pyrolysis was used for organic matter fractions in the sediment cores,and fatty acid data in two of the cores were also used to study the biological pump effect of algal organic matter on the sedimentation of PBDEs.The historical variations of PBDEs and their links with those of algae organic matter and climate warming were investigated.In addition,the desorption behavior of BaP in surface sediments in aquatic environment were also investigated.Elemental analysis,solid-state ¹³C nuclear magnetic resonance?NMR?,and carbon dioxide gas adsorption method were used to characterize the sedimentary organic matter fractions,so as to explore the relationships of the desorption parameters of BaP with the composition,structure,and nanoporosity of organic matter fractions.LHH is a hyper-eutrophic lake while LA is a meso-eutrophic reservoir.The levels and seasonal variation of PBDEs in algae and zooplankton in LHH and LA were quite different.The contents of PBDEs were significantly higher in LHH than in LA.The seasonal variation patterns were related to temperature,rainfall,and sediment resuspension.Moreover,plankton biomass and eutrophication status in LHH and LA play dominant roles on the bioaccumulation of PBDEs in planktons.The seasonal variation of T-SPM fluxes showed great differences.The seasonal variation of PBDE fluxes were closely related to TOC fluxes and T-SPM fluxes,which were influenced by atmospheric deposition,water level,rainfall,and sediment resuspension.The bottom fluxes were far greater than the upper fluxes,which were influenced by sediment resuspension and lateral transportation of T-SPM.Rock-Eval pyrolysis is a good method to analyze aquatic organic matter.The correlation analysis showed the organic matter in T-SPM was mainly derived from algal organic matter.In addition,algal organic matter in LA and LHH made an dominant contribution to the sedimentation of PBDEs.The levels of PBDEs in the surface sediments of different regions are in the following sequence:LHH,LA,XFJ and DYW in South of China>JBH and XKH in Northeast of China>LGH and CHH in Southwest of China,which were related to the industrial development,the distance to cities,sewage discharge,and atmospheric deposition.The pyrolytic parameters such as S2,hydrogen index?HI?,and TOC are significantly correlated with each other in the each of sediment cores,suggesting a significant contribution of algal organic matter in these lakes.Algal organic matter contents in LA,LHH,XFJ,CHH,and XKH cores were significantly related to contents of PBDEs,indicating the dominant effect of algal productivity on PBDEs deposition.FAs in the LA core significantly correlated with algae-derived organic matter and PBDEs,suggesting the proxy of FAs as an good algae source.In addition,climate change could enhance the primary productivity in the investigated LA and XFJ,and thus influence the deposition of PBDEs.Finally,by comparing the settling fluxes and sedimentation fluxes of PBDEs,it was found that low brominated BDEs were more likely to recycle at the bottom,while high brominated BDEs were easily buried in the sediments.Finally,the desorption kinetics and mechanism were investigated using a Tenax extraction technique on different sediments spiked with radiocarbon-labeled benzo?a?pyrene?BaP?.Results showed that the sediments contained high percentages of algaenan and/or sporopollenin but low percentages of black carbon and lignin.A first-order,two-compartment kinetics model described the desorption process very well?r²>0.990?.Although some of the organic carbon fractions were significantly related to the desorption kinetics parameters,the NHC fractions showed the highest correlation.The multiple regression equations among the desorption kinetics parameters,structural parameters,and nanoporosity were well established.Nanoporosity and aromatic C were the dominant contributors.Furthermore,the enhanced percentages of desorbed BaP at elevated temperatures significantly showed a linear regression with the structure and nanoporosity.To our knowledge,the above evidence demonstrates for the first time that the transfer?or diffusion?of BaP in the nanopores of condensed aromatic components is the dominant mechanism of the desorption kinetics of BaP at organic matter particle scale.