Emission patterns and spatiotemporal variations of halocarbons in the Pearl River Delta region, southern China

Abstract

On 8 selected days between 25 October and 1 December 2007, 198 whole air samples were simultaneously collected at two sites in the greater Pearl River Delta (PRD), namely, Wan Qing Sha (WQS) in inland PRD and Tung Chung (TC) in Hong Kong, for the evaluation of halocarbons including chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and other chlorinated compounds. The mean mixing ratios of CFC-12, CH₃CCl₃, CH₃Br, C₂HCl₃, and C₂Cl₄ at WQS were much higher than those at TC (p < 0.001), while HCFC-22 was higher at TC (p < 0.01). Long-lived species such as CFC-11, CFC-12, and CFC-113 showed similar temporal patterns on most sampling days with small daily variation, whereas the main species used as solvents such as C₂HCl₃ and C₂Cl₄ presented large daily variations though with consistent temporal patterns. Source profile analysis revealed that although there was no remarkable change in emission sources between 2001–2002 and 2007, the emissions of CFCs and CCl₄ from the production of refrigeration in 2007 were 1.4–2.0 times those in 2001–2002, and the use of HCFC-22 has significantly increased in these years while the use of C₂HCl₃ and C₂Cl₄ in the electronics industry showed a remarkable reduction. By comparing the halocarbon data collected in this study with those observed by other research teams in recent years, we found that the levels of CFCs have declined since 2001, while their substitute HCFC-22 has increased in emissions in recent years, especially in Hong Kong. The annual trends are consistent with the implementation of the Montreal Protocol. The results obtained in this study provide useful information to local government on effective control of halocarbon emissions in this region.