Abstract
During this study 158 whole air samples were collected in 45 Chinese cities in January and February 2001. The spatial distribution of different classes of halocarbons in the Chinese urban atmosphere, including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), Halon-1211, and other chlorinated compounds is presented and discussed. Most of these compounds were enhanced compared to background levels. However, the mean enhancement of CFCs was relatively small, with CFC-12 and CFC-11 increases of 6% (range 1–31%) and 10% (range 2–89%), respectively, with respect to the global background. On the contrary, strongly enhanced levels of CFC replacement compounds and halogenated compounds used as solvents were measured. The average Halon-1211 concentration exceeded the background of 4.3 pptv by 75% and was higher than 10 pptv in several cities. Methyl chloride mixing ratios were also strongly elevated (78% higher than background levels), which is likely related to the widespread use of coal and biofuel in China.
Highlights
Halocarbons are an important sub-class of VOCs, and the emissions of many halocarbon species are regulated by the Montreal Protocol and its subsequent amendments because of their potential to deplete stratospheric ozone (WMO, 2002; UNEP, 2003)
The total tropospheric burden of bromine is much less than the chlorine burden, stratospheric ozone depletion by bromine is an important process because a bromine atom is about 50 times more effective at destroying stratospheric ozone than a chlorine atom (Montzka et al, 2003)
In collaboration with the Hong Kong Polytechnic University (HKPU) and Zhongshan University, a total of 158 whole air samples were collected in 45 cities in China in January and February 2001 (Fig. 1) using evacuated 2-L stainless steel canisters each equipped with a bellows valve
Summary
Transported into the stratosphere where they are photolyzed. The chlorine and bromine atoms released through photolysis can initiate catalytic cycles leading to stratospheric ozone depletion (WMO, 2002). By 2001, when this study took place, many of the halocarbons discussed here had been phased out in developed countries under the Montreal protocol and subsequent amendments (by 1 January 1996 a 100% reduction of the base levels of production and consumption was established for many halogenated compounds), but were allowed to be produced and consumed in developing countries (UNEP, 2003). Mainly bromochlorodifluoromethane (Halon-1211), 1,2-dibromotetrafluoroethane (Halon2402) and bromotrifluoromethane (Halon-1301) have been used as fire-fighting chemicals (Butler et al, 1998), and are one of the most important anthropogenic source of bromine atoms in the stratosphere (Montzka et al, 2003). Emissions of halocarbons from the industrial sector are interesting because China is one of the most populated, industrialized and fastest developing countries classified in the Montreal Protocol’s ‘‘Article 5 parties’’ (developing countries still allowed to produce CFCs, halons and other halocarbons). In this study mixing ratios of 19 halocarbons measured in the urban atmosphere of 45 Chinese cities are presented and discussed
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