| There has been a great concern about the global transport of persistent organic pollutants (POPs). POPs are semi-volatile organic pollutants having long half-life in the environment and may pose negative impact on human health and ecosystems. They are able to transport in the atmosphere even to the places far away from where they are used/discharged. Typical POPs include organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polyborminated biphenyl ether (PBDEs) and polycyclic aromatic hydrocarbons (PAHs). While many studies have been conducted in Arctic, Antarctic, North America and Europe on long-range atmospheric transport (LRAT) of POPs, little was reported in China. The objective of this preliminary study was to monitor potential LRAT of PAHs and OCPs, using an approach of consecutive active sampling and air mass back trajectory analysis, at Mt Waliguan Global Baseline Observatory in northwestern China, and at Qingdao downwind of North China.In the first part of the thesis, the atmospheric characteristic of PAHs and OCPs at Mt Waliguan was studied. 24 hr air samples were collected consecutively from April 2 to May 23, 2005. In total, 26 paired vapor and particle samples were collected during the sampling periods. The PAH total concentrations in the gas phase varied from 7.0 to 26.1 ng/m3, with an average of 17.1 ng/m3. Considerably lower concentrations were observed for particulate PAHs, ranging from 0.3 up to 7.8 ng/m-3, with an average of 2.1 ng/m3. The average concentrations ofα-HCH,γ-HCH, HCB, TC, CC, o,p '-DDT, p,p'-DDT and p,p'-DDE in the atmosphere of were 58.4±24.4 pg/m3,139±58 pg/m3, 38.4±19.1 pg/m3, 18.1±11.8 pg/m3, 22.1±l5pg/m3, 17.9±20.3 pg/m3, 4.4±5.7 pg/m3 and 5.1±4.8 pg/m3, respectively. In general, the levels of OCPs were slightly higher than those observed in other remote area, such as the Arctic, Antarctic. The low temperature dependence of the POP concentrations in the air, and the absence of local use of these compounds implied long-range atmospheric transport to Waliguan. As suggested by backward air trajectory analysis, the high concentrations ofγ-HCH and DDTs, during the sampled spring period, were mainly related to air mass passing over the neighbouring countries (e. g. Russia, Kazakhstan).In the second part of the thesis, the atmospheric OCPs characteristic at Qingdao was determined. A modified Anderson-type Hi-Volume air sampler was operated at a rate of 288 m3 day-1. 24hrs air samples were collected consecutively from April 19 to May 21, and every one week between June 2005 and March 2006. In sum, 60 particle samples and 60 PUF samples were collected. The average concentrations ofα-HCH,γ-HCH, HCB,TC, CC, HEP, o,p'-DDT,p,p'-DDT and p,p '-DDE in Qingdao air were 77.3±41 pg/m3, 289±236 pg/m3, 220±186 pg/m3, 91.2±105 pg/m3, 398±312 pg/m3, 31.2±18. 9 pg/m3, 80.6±62.4 pg/m3, 54.6±49.2pg/m3 and 59.5±44 pg/m3, respectively. The concentration levels were much lower than those observed at Tianjing and Guangzhou. In general, the concentrations of OCPs increased from the spring-winter to the summer-autumn except for HCB which had no clear seasonal pattern. The relatively low slope and temperature dependence (R2<0.4) suggested that the concentrations of OCPs at Qingdao just can be partly explained by temperature difference. 5 days back trajectory indicated that unusually high air concentrations of OCPs were detected during the Asian dust episodes, and relatively low concentrations of OCPs were observed when relatively clean air mass came from the yellow sea. |
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