Source Apportionment Of Persistent Toxic Substances In Typical Environmental Media By Receptor Modeling: Polycyclic Aromatic Hydrocarbons, Dioxins And Polychlorinated Biphenyls

Receptor models assess contributions from all the major sources based on observations at sampling sites,the "receptors".Receptor models have been widely used for source apportionment of pollutants in various environmental media.Many different receptor modeling methods are available,such as factor analysis/multiple linear regression(FA/MLR), chemical mass balance(CMB),positive matrix factorization(PMF) and factor analysis with non-negative constraints(FA-NNC).In this study,FA-NNC was modified and verified its applicability.The levels,compositions and sources of atmospheric polycyclic aromatic hydrocarbons(PAHs),pine needle polychlorinated dibenzo-p-dioxins/ dibenzofurans (PCDD/Fs) and polychlorinated biphenyls(PCBs) in Dalian and sediment PAHs in Baiyangdian were investigated.FA-NNC and PMF were adopted to apportion their sources.FA-NNC is one of the advanced receptor models.It has been used for source apportionment of organic pollutants by many researchers.However,it was reported that in some cases,FA-NNC could not converge,indicating the limits of the robustness of FA-NNC. In this study,FA-NNC was modified and verified by using artificial data set created by Monte Carlo simulation and real world data set.The robustness of FA-NNC was enhanced after modification.Furthermore,the model can offer more information of the pollution source and successfully predict the source fingerprints.Positive matrix factorization(PMF) was used to verify the effectiveness of the modified FA-NNC.Results from PMF and the modified FA-NNC were consistent,indicating the effectiveness of the modified FA-NNC.It was successful to employ FA-NNC and PMF for source apportionment of PCDD/Fs and PCBs in pine needles in Dalian.The source profiles derived from the two receptor-models were almost the same.In Dalian,the main sources of PCDD/Fs were estimated to be various combustion processes(58%～74%),PCP contamination(15%～17%), metal metallurgy(9%～12%),and traffic emissions(2%～13%).As for PCBs,two similar source profiles were identified by the two receptor-models.One source profile that is similar to Aroclor1242 represents China's technical PCB product PCB3(72%～80%),and another source profile that is similar to Aroclor1254 represents the product PCB5(20%～28%).The source contributions are qualitatively consistent with the proportions of technical PCB products synthesized and used in China. The average PAH levels in Dalian was comparable to that found in some international cities and lower than those reported for several northern Chinese cities.Obvious seasonal variations in the PAH concentrations were observed,with maximum and minimum concentrations in heating and non-heating period,respectively.It was successful to employ FA-NNC combined with local and literature PAH source profiles for source apportionment of atmospheric PAHs.The source apportionment results by the FA model with nonnegative constraints showed that PAHs originated from coal related sources mainly(89%) and followed by traffic emissions(11%) in heating period,and in non-heating period,traffic emissions is the major PAH contributor(79%),and coal-fired power plant as a second source (21%).The average sediment PAH level in Baiyangdian area was lower than that found in some other sediment samples worldwide.This indicates that the environment of Baiyangdian area was slightly contaminated by PAHs.Distinct patterns were found in upper and lower sediment samples,with high molecular weight PAHs(5 or 6 rings) mainly in upper sediment samples and low molecular weight PAHs(2 or 3 rings) in lower sediment samples,which indicated that the main sources of PAHs were changing with time.Results of FA-NNC showed that residential coal(31%) and biomass burning(39%) were the main PAH source in Baiyangdian area,followed by coal fired power plants(17%) and traffic emissions(13%).