Project No: 16306224

Title: Observational study of short-lived halocarbons in a coastal suburban environment

Principal Investigator: Prof. Dasa GU

Abstract:

Halocarbons are primary cause of stratospheric ozone layer depletion and pose serious health risks, making them a priority for research since the 1970s. Furthermore, halocarbons are increasingly acknowledged to exert significant influences that affect both climate and air quality. The collective implementation of international agreements (e.g., Montreal Protocol) has controlled the production of most long-lived halocarbons (e.g., chlorofluorocarbons (CFCs), halons), and their abundances are slowly declining. However, there remains significant uncertainty on the rate of ozone layer recovery. One key uncertainty is the increasing emissions of uncontrolled short-lived halocarbons (SLHs) with a lifetime less than six months, as highlighted in the WMO Assessment of Stratospheric Ozone Depletion. As some short-lived halocarbons can reach the stratosphere through deep convention, it was suggested that they may delay the recovery of the stratospheric ozone hole by decades. Despite their ubiquitous presence, SLHs remain subject to substantial uncertainties regarding their abundances, emissions, and environmental impacts due to the paucity of continuous measurements. While SLHs can be emitted from complicated nature sources, recent studies suggested there was rapid and unexpected increase of anthropogenic emissions, especially in eastern and southeastern Asia. Based on our previous study results, we found there is a critical need for continuous measurement of SLHs in Hong Kong. In this proposed project, we plan to study the characteristics of major SLHs by conducting long-term measurements on a daily basis at a coastal suburban site in HKUST. Combining intensive measurements during episodic events, we will analyze the potential contributions from complicated emission and transport processes on their temporal variations. Utilizing observation data, we will conduct top-down emission estimation through both interspecies correlation method and Bayesian interference method, while emission results and uncertainties will be compared and assessed. The long-term observation data and emission estimates obtained from this project will provide valuable information in improving modeling the interactions between anthroposphere and biosphere.