Project No: 26304921

Title: Study of ambient halocarbons in Hong Kong: temporal variability and implication on source origins

Prof. Dasa GU


Halocarbons have been recognized for their role as major ozone depletion substances (ODSs) since the 1970s, while some of them also function as greenhouse gases (GHGs). International agreements, such as the Montreal Protocol, Kyoto Protocol, and Paris Agreement, were established for worldwide cooperation to gradually reduce the production and use of halocarbons. Initial success was achieved in phasing out global chlorofluorocarbons (CFCs) productions, but recent studies found an unexpected slowdown in the decline of the atmospheric concentration of trichlorofluoromethane (CFC-11) after 2012. Based on measurements from several locations in East Asia combining with global background observations, the increase in CFC-11 emissions from eastern China was suggested to account for up to 60% of the total increasing emission worldwide. However, the remaining fraction is unexplained because of the lack of long-term measurement. Historically, halocarbons have been emitted from various anthropogenic sources (e.g., dry cleaning industry, electronic industry, and refrigeration) in Hong Kong. Emission sources in the Pearl River Delta (PRD) region, such as chemical manufacturing, also have remarkable impacts on the ambient halocarbons in Hong Kong. The ambient mixing ratios of major CFCs were declining in Hong Kong and the PRD region before 2010. However, no continuous measurements on ambient halocarbons were conducted in Hong Kong after 2010. Given that CFC emissions from the PRD region account for up to 25% of their total emissions in China, any unexpected CFC emissions in the recent year can introduce significant impacts on atmospheric abundances of halocarbons worldwide. In this work, we propose to set up a framework for long-term measurement on ambient halocarbons, and generate 3-year data on ambient abundance of major ODS and GHGs at our supersite. The goal is to study the temporal variability of ambient halocarbons and estimate their source origins using multiple modeling approaches. The contribution from local and regional sources to their ambient presence will be investigated.