Methods Establishment Of Compound-Specific Radiocarbon Analysis And Its Application In Source Identification Of Polycyclic Aromatic Hydrocarbons

Natural compound-specific radiocarbon analysis(CSRA)and its application is currently at the forefront of earth science research and is also an effective method for studying biogeochemical processes of organic carbon.In this study,we established a pre-treatment method for the CSRA in the domestic laboratory and apply it to study the source identification of PAHs in seawater and sediments.It is expected to provide a new method and idea for the evaluation of marine pollution.This study mainly achieved the following conclusions.A pre-treatment method for the CSRA of the trace organic matters has been established.This method mainly includes:bluk sampling,organic extraction,component separation and purification,preparation of monomeric hydrocarbons by preparative capillary gas chromatography,construction of vacuum line-graphite reactor,catalytic oxidation of organic matters,purification,quantification,and graphitization of CO2.We also focused on the quality control and assurances of each step.The pretreatment results showed that Flu,Phen+An,Fuo and Py were successfully separated from seawater.The carbon masses of these compounds were 1.8-5.0 ?mol,and the averaged purities were 96±2%.Phen+An,Fluo+Py,5+6 rings,and Perylene were successfully separated from the sediments and the carbon masses were 2.1-6.0 ?mol,and the averaged purities were 95±3%.We applyed the CSRA to identify the source appointment of dissoveld PAHs in the seawater of the Taiwan Strait.The results showed that the ?14C values of monomeric PAHs in the water masses of the Taiwan Straits were-997‰ to-873 ‰,indicating the input characteristics of relatively consistent fossil fuel PAHs.The ?14C values of each monomer PAHs are as follows:South China Sea Warm Current(SCSWC)>Min-Zhe Coastal Current(MZCC)>Xiamen Western Harbour Water(XMWH)>Joulong River Estuary Diluted Water(JRDW).Based on the 14C mass balance,the percentages of monomeric PAHs contributed by biomass combustion in the water masses of the Taiwan Strait were very low.The proportion of biogenic PAHs in the seawater of JRDW,XMWH,MZCC,and SCSWC averaged 10± 0.5%,7.5±0.7%,2.8 ± 0.8%,and 1.710.6%.The source characteristics of PAHs were directly related to the PAHs characteristics of anthropogenic emissions in the Taiwan Strait and its surrounding sea areas and land(mainly fossil fuel and their combustion emissions).We also applied CSRA technology to study the souces of PAHs in sediments from the estuarine to offshore environment.In the sediments of the Jiulongjiang Estuary and Western Taiwan Strait,the ?14C distribution of monomeric PAHs was from-849‰ to-18‰,indicating that the fossil source contribution remains the main source of PAHs in estuarine and offshore sediments,with an average contribution rate of approximately 72%±11%.Those were significantly less than the ?4C values(-906‰ to-873‰)of each monomer PAHs in the water-dissolved phase.It showed that the transport process of PAHs from surface seawater to sediments enriched lighter carbon gradually.This might be owing to that the suspended biomass particles are more easily absorbed or adsorbed lighter carbon and buried.Except for PeryleneG the ?14C values of the offshore of the Jiulong River estuary to the Western Taiwan Strait gradually decreased with the increase of the ring number of sediment PAHs,those were the proportion of decayed carbon(or fossil fuel source)gradually increased.That might be because the proportion of PAHs contributed by fossil sources increased with the ring number of PAHs,or that high molecular weight PAHs were more likely to be adsorbed by particles or absorbed by organisms and buried in sediments during the bury into the sediment of PAHs contributed by the release of fossil sources such as oil leakage or combustion.In addition,during the transport of perylene from the estuary to offshore,the biomass contribution decreased significantly from 40%to 23%,indicating that the intensity of land-sourced actions gradually weakened,and indirectly indicating the significant increases of perylene input from the direct discharge of fossil fuel.