Traffic-source Polycyclic Aromatic Hydrocarbons (PAHs) And Polychlorinated Dibenzo-p-dioxin (PCDD) And Polychlorinated Dibenzofuran (PCDF) In Guangzhou

Vehicles can emit many kinds of persistent organic pollutants, which contain polycyclic aromatic hydrocarbons (PAHs) and polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF). They draw people much attention because of their high toxicity, persistent, bioaccumulate in human and animal tissue, semi-volatile and long-range transport character, which can do a lots harm to people's health. This research aimed to find out the vehicle emission character of the Polycyclic aromatic hydrocarbons and Dibenzo -p-Dioxins and Dibenzofuran, as well as the process from source to receptor. This research chose the Pearl River tunnel and Hunan fast-road as the research area. This study collected April, July, December Pearl River Tunnel samples, including particulate and gaseous phase, as well as the ambient air samples. At the same time, this research also collected 12 months atmospheric deposition samples from roadside. Through analyzing, the PAHs concentrations of the tunnel samples ranged from 896.1 ng·m^-3 to 4066.2 ng·m^-3; PAHs in gaseous phase were far higher than those in the particulate phase. Compared to the ambient air samples' concentrations, which was ranged from 207.9 ng·m^-3-353.0 ng·m^-3, the ambient air samples' concentrations were far lower than the tunnel samples'. The PAHs congeners distribution of the ambient air samples was similar to the tunnel samples. It indicates that automobile emission is a very important source of PAHs in Guangzhou atmosphere. In summer, the PCDD/Fs concentrations in tunnel ranged from 3830.9 fg·m^-3 to 4690.2 fg·m^-3(193.0 fg·I-TEQ·m^-3-217.0 fg·I-TEQ·m^-3); In the winter, the concentrations in tunnel ranged from 18600.8 fg·m^-3-20388.8 fg·m^-3(1275.38 fg -I-TEQ·m^-3-1392.17 fg·I-TEQ·m^-3). The ambient air concentrations were lower than the tunnel samples. The concentrations of site B, site A, site C and site D in Pearl River Tunnel and its adjacent ambient air had a tendency of decline. Especially in winter, the tunnel air had a PCDD/Fs TEQ concentration about five times as high as that of outside air. This provides the evidence that the PCDD/Fs in the air are at least partly emitted from the combustion processes of gasline- and diesel-fueled cars. Utilizing the data of the tunnel samples, the emission factor (EF) was calculated. The mean EF of PAHs and PCDD/Fs in Guangzhou was 2164.7 ug·km^-1·vehicle^-1 and 1994.56 pg·km^-1·vehicle^-1(104.83 pg I-TEQ). According to these EF data, the PAHs and PCDD/Fs emission from automobiles in Guangzhou was estimated as 82t and 75.5g (3.97g I-TEQ) per year.Eleven atmospheric deposition samples were collected from 2006-01-01 to 2006-12-31 every month. The 12 months atmospheric deposition flux data indicated that the mean atmospheric deposition flux of PAHs and PCDD/Fs were 8.66 ug·m²Â·d and 1119.93pg·m^-2·d^-1 (32.57 pg TEQ m^-2·d^-1 ) respectively. This research also discussed the photolysis influence to the process of the sampling by adopting two different sampling equipments, as well as collecting daytime and nighttime sample respectively.