| Dibenzo-p-dioxins and dibenzo-furans (PCDD/Fs) and polychlorinated biphenyls (PCBs) are two groups of persistent organic pollutants (POPs) that are widely distributed in the environment. These two groups of compounds are both quite stable in environment, and can be accumulated in the fatty tissue of living organisms and showed high toxicity at very low levels. Atmosphere is the major pathway for these chemical pollutants to transport and redistribute in the environment. Studies on emission, concentration and environmental chemical behavior of dioxin-like POPs are all important research directions. Among them, research on the environmental chemical behavior of dioxin-like POPs in environmental media was not enough, so study on environmental chemical behavior of dioxin-like POPs in typical region was significant.In this study,20atmospheric samples and25soil samples were collected in summer and winter in Shanghai. By using isotope dilution/high resolution gas chromatogr aphy/high resolution mass spectrometry method, the concentrations, profiles, gas-particle partitioning, vertical distribution and soil-air exchange of PCDD/Fs and doxin-like PCBs in Shanghai were studied. It mainly includes thses parts as follows:Atmospheric concentrations of dioxins in summer and winter were258-2,009fg/m3and315-4,928fg/m3, the TEQ was9.43-88.5fg-TEQ/m3and15.0-423fg-TEQ/m3respectively. Atmospheric concentration of dioxins-like PCBs in summer and winter were370-4,877fg/m3and1041-7,474fg/m3, and the TEQ were1.79-17.0fg-TEQ/m3and5.26-55.9fg-TEQ/m3respectively. It showed a clear seasonal trend that concentrations of dioxins like POPs in winter were significantly higher than those of summer. The concentrations of individual congeners followed the same spatial change trends in same season. The higheast concentrations were found in industrial area and the lowest concentration were found in control point.The results of studies on gas-particle partitioning of PCDD/Fs and PCBs indicated that PCBs were primarily distributed in gas and PCDD/Fs were primarily bounded in particle. LogKp and logPL0of PCDD/Fs and PCBs presented obvious linear relativity. Overall, gas-particle partitioning of PCDD/Fs and dl-PCBs was better simulated by Jungee-Pankow than octanol/air partition coefficient-based model.The results of reverse trajectories and principal component analysis showed that the monomer dioxins distribution characteristics were influent by nearby atmospheric emission sources in Shanghai and the influence from secondary aluminum industry and electric arc furnace steelmaking sources were quite outstanding.Concentrations of dioxins in soil showed that roadside soil>farmland area>residential areas; whereas the concentration of dl-PCBs in soil showed the urban industrial areas>suburban industrial area>residential areas>suburbs. Concentrations of dioxins in northern regions were higher than those of southern areas.The results from the soil-air exchange model showed that dioxins exhibited net absorptions from the air to the soil, whereas lower chlorinated PCBs presented a net absorption from the soil to the air, high chlorinated PCBs (PCB169and189) presented net absorptions from the air to the soil.In this study the health risks of PCDD/F and dl-PCBs exposure were assessed for adults and children in summer and winter in Shanghai. Dioxin intake from breath showed that children exposure to dioxin-like POPs greater than the risk of exposure to adults, and intake of dioxins like POPs in winter was greater than in summer. But on the whole, the daily dioxins inhalation exposure for adults and children in Shanghai is approximately equal to Guangzhou and Dalian. |
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