Halogenated hydrocarbons (halocarbons) play important roles in global warming and stratospheric ozone depletion due to their long atmospheric lifetimes, and they have been a research priority since the middle of last century. This study investigates the temporal and spatial variations of halocarbons in Hong Kong and their potential source origins. Overall 209 monthly samples were collected at three ground sites in Hong Kong, including HKUST Supersite Station (UST), Yuen Long (YL), and Tai Po (TP) from August 2020 to July 2022. In addition, 683 daily samples were collected at UST from November 1, 2020 to June 30, 2021. Seventeen halocarbon species were investigated in this thesis with three categories: Montreal Protocol (M-P) banned species (e.g., CFCs, CCl₄, and CH₃Br), M-P controlled s...[ Read more ]

Halogenated hydrocarbons (halocarbons) play important roles in global warming and stratospheric ozone depletion due to their long atmospheric lifetimes, and they have been a research priority since the middle of last century. This study investigates the temporal and spatial variations of halocarbons in Hong Kong and their potential source origins. Overall 209 monthly samples were collected at three ground sites in Hong Kong, including HKUST Supersite Station (UST), Yuen Long (YL), and Tai Po (TP) from August 2020 to July 2022. In addition, 683 daily samples were collected at UST from November 1, 2020 to June 30, 2021. Seventeen halocarbon species were investigated in this thesis with three categories: Montreal Protocol (M-P) banned species (e.g., CFCs, CCl₄, and CH₃Br), M-P controlled species (e.g., HCFCs and HFCs), and non-regulated species (e.g., short-lived halocarbons).

For M-P banned species, their concentrations in Hong Kong presented minimal enhancements above the background levels, demonstrating the effectiveness of the Montreal Protocol implementations. Non-regulated species with short lifetimes presented the most significant enhancements above the background levels, suggesting the needs of further regulations. In terms of seasonal variations, the M-P banned species exhibited little changes, while regulated species were more prevalent in summer, and non-regulated species were higher in winter. Comparing between three monitoring sites, YL has the highest halocarbon concentrations, followed by TP and UST. The Positive Matrix Factorization (PMF) results from the three sites also indicate that refrigeration sources contributed more at the urban site YL, while natural sources were more prevalent at the suburban site UST. The Potential Source Contribution Function (PSCF) results suggest significant transport influence from Yangtze River Delta (YRD) to observed C₂HCl₃, C₂Cl₄, and HFC-134a, and important impacts from Fujian to observed HCFC-141b. Finally, the investigation of long-range transport effects in the daily samples collected at UST revealed that solvent usage was mainly located in eastern China, while impacts from refrigeration replacements were found in western Guangdong and Hong Kong’s surrounding regions. This study offers valuable insights into the efforts to implement the Montreal Protocol in Hong Kong and the surrounding areas, emphasizing the need for continual control of halocarbon emissions.