Chlorofluorocarbons, hydrochlorofluorocarbons, and hydrofluorocarbons in the atmosphere of four Chinese cities
2013
Wu, Jing | Fang, Xuekun | Xu, Wanyun | Wan, Dan | Shi, Yehong | Su, Shenshen | Hu, Jianxin | Zhang, Jianbo
From July 2009–April 2011, 304 whole-air samples were collected at urban and suburban sites in four Chinese cities. The results indicated that recent chlorofluorocarbon (CFC) concentrations in all four cities are approaching Northern Hemispheric (NH) background levels, suggesting that the phase-out of CFCs in China is underway. However, hydrochlorofluorocarbon (HCFC) and 1,1,1,2-tetrafluoroethane (HFC-134a, CH2FCF3) concentrations have risen far above the NH background levels. Their concentration variability is evident, suggesting significant regional emissions. One-way analysis of variance (ANOVA) and independent-sample t-tests were applied to analyze the spatial distributions and emissions. Monochlorodifluoromethane (HCFC-22, CHClF2) levels at the urban sites were 30% higher than those observed at the suburban sites (P < 0.05), likely owing to larger population density in the urban areas. The largest 1-dichloro-1,1-fluoroethane (HCFC-142b, CH3CClF2) mean concentrations were detected in Beijing (131 and 52 pptv for urban and suburban sites, respectively), likely because of more widespread use of extruded polystyrene board. The variation in HFC-134a concentration levels in different cities was mainly related to the vehicle population. In addition, the different HCFC species exhibited significant positive correlations amongst themselves for each city (P < 0.05), suggesting that either they were emitted from similar or co-located sources or they shared similar emission patterns. These results are helpful to confirm the phase-out of ozone-depleting substances (ODSs) and to provide guidance for implementing effective phase-out strategies for ODSs and greenhouse gases.
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