Analytical Method And Preliminary Study On Environmental Behavior Of PCDD/Fs And DL-PCBs In Environmental And Biological Samples

Tremendous increase in economy, industrial productivity and energy consuming, has resulted in serious problems of environmental pollution. Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo-furans (PCDD/Fs), or dioxin-like polychlorinated biphenyls (DL-PCBs), emitting from Electron waste incineration, municipal solid waster incineration and vehicle exhaust, etc., are great hidden troubles to environment and human health. It is of great importance to carry out some research on PCDD/Fs and DL-PCBs in environmental and biological samples, and then provide a guide to limit emissions and take measures to reduce or eliminate them.In developed countries, great efforts have been made to research on dioxins sources and environmental geochemistry behaviors, yet few in China, especially for DL-PCBs. Thus, in order to build a reliable analytical method of PCDD/Fs and DL-PCBs in environmental and biological samples, survey and assess their pollution level, identify their source and explore their environmental behaviors, we present the major research content in the study: (1) The analytical methods are built to determine PCDD/Fs and DL-PCBs in environmental and biological samples; (2) The pollution level of PCDD/Fs and DL-PCBs are primarily surveyed and assessed in some food, and these compounds are compared those in local environmental samples; (3) Atmospheric deposition fluxes of PCDD/Fs are determined, their spatial and temporal variations are investigated, and the relationships of PCDD/F deposition fluxes between meteorological and environmental factors are analyzed; (4) the source of PCDD/Fs in atmospheric deposition is roughly identified and PCDD/Fs environmental behaviors are primarily explored.A modified analytical method, based on EPA1613, was built to determine PCDD/Fs in environmental samples. Samples were cleaned up successively with acid silica gel, a multi-layer silica gel column and a basic alumina column. PCDD/Fs were determined with GC-HRMS. Precise and recoveries of the entire procedure were evaluated by replicate analysis (n=4) of PCDD/Fs standard solutions, with RSD below 7.1% and the recoveries in the range of 62-103%. The method was also validated by replicate analysis (n=3) of certified reference material. The found values were in agreement with those certified with the RSD below 15%.Based on the above analytical method, another analytical method is built to simultaneously determine PCDD/Fs and DL-PCBs in environmental samples. Samples cleaned with acid silica gel and a multi-layer silica gel column. A fiorisil column is used to separate PCDD/Fs and DL-PCBs, and a gel permeation chromatography column is used to eliminate high molecular interferences in sediments and soils. Precise and recoveries of the entire procedure is evaluated by replicate analysis (n=4) of PCDD/Fs and PCBs standard solutions, with RSD below 8.9% and 11.4% for PCDD/Fs and PCBs respectively, and with the recoveries in the range of 60-105%. These compounds are successfully analyzed in environmental samples such as sediment, slurry, soil and fly ash from 11^th round of international intercalibration study.Past research shows that the contribution of DL-PCBs to total TEQ is comparable with that of PCDD/Fs, and more than 90% of TEQ in human body is resulted from food, especially animal food. Large amounts of solvent and acid silica gel are used repetitiously to eliminate the lipid in food based on the phase distribution. PCDD/Fs and DL-PCBs in extremely low level are determined in poultry, egg, pork and ham with a larger sample amount. Homologue or congener profiles of these compounds in these foods are similar to each other, although the interested compounds are in obviously different level, indicating that the source is difficult to be identified. Lower chlorinated PCDD/Fs are more likely to be accumulated in biology.Atmospheric deposition is an important pathway for the loading of PCDD/Fs to environmental sinks. Atmospheric deposition of PCDD/Fs in Guangzhou city is investigated, based on the research on PCDD/Fs in ambient air, soil and sediment. The annual deposition fluxes of tetra- to octa-CDD/Fs (total PCDD/Fs) were found to range from 170-3000 (mean 1500) pg m^-2 day^-1, and the fluxes of total 2,3,7,8-substituted PCDD/F congeners ranged from 2.1-41 (mean 20) WHO-TEQ m^-2 day^-1 at Wushan. The average deposition fluxes of total 2,3,7,8-substituted PCDD/F congeners in rainy season were found to be 37, 27 and 28 pg WHO-TEQ m^-2 day^-1 at Yuancun, Haizhu and Changban, respectively. PCDD/Fs deposition fluxes in Guangzhou were comparable or higher than those in other regions. It was found that the profiles of PCDD/F homologues or congeners in the samples were the same either spatially or temporally, indicating that the PCDD/F emission sources were similar to one another. The PCDD/F deposition fluxes behaved obviously higher in rainy season than in dry season. Results from regression analysis showed that number of rainy days, the amount of wet precipitation, PCDD/F concentrations in particles and organic carbon content played important roles in the variation of PCDD/F deposition fluxes. Monthly average temperatures change little from January to December. Therefore, it only played a minor role in monthly variation of PCDD/F deposition fluxes. Particle deposition fluxes were generally not considered as the factor that could cause the differences in PCDD/F deposition fluxes between rainy and dry seasons, but were found to be related with PCDD/F deposition fluxes in rainy season or dry season. The similarities in PCDD/F homologue patterns and the differences in deposition fluxes between samples collected from heavy-traffic roadside and nearby residence house roof indicated that vehicle exhaust might be an important source for PCDD/F in Guangzhou. PCDD/F concentrations and profiles of PCDD/F homologues in atmospheric deposition were compared with those in both total suspended particles in air and soils, and conclusions indicated that atmospheric deposition possibly tended to remove lower chlorinated DD/Fs from air and was one of sources for PCDD/Fs in soils.