Enhanced chlorinated very short-lived substances in South East Asia: Potential source regions and source types

Norfazrin Mohd Hanif, Claire E. Reeves, David E. Oram, Matthew J. Ashfold, Marios Panagi, Zoe L. Fleming, Lauren J. Gooch, Johannes C. Laube, Azizan Abu Samah, Ahmad Amin Abdullah, William T. Sturges

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Abstract

Enhancements of the mixing ratios of short-lived halogenated gases were observed in air samples collected at Bachok Marine Research Station (BMRS), Peninsular Malaysia during Northern Hemisphere winters in 2013/2014 and 2015/2016. This study investigates the potential source regions and source types that influenced the variability in chlorinated very short-lived substances (Cl-VSLS) [dichloromethane, 1,2-dichloroethane, trichloromethane, tetrachloroethene] and methyl halides [methyl chloride and methyl bromide]. The UK Met Office’s Numerical Atmospheric Modelling Environment (NAME) dispersion model, was used for tracking the origin of air masses arriving at BMRS. For the purpose of identifying possible sources of these compounds, carbon monoxide (CO) emission data taken from the Representative Concentration Pathway 8.5 were used along with NAME footprints to calculate modelled CO mixing ratios. A correlation analysis between the mixing ratios of measured compounds and the modelled CO from various emission sectors was perform to assess the extent to which emission sectors might be related to the mixing ratios of halogenated gases. The results show that the events of higher mixing ratios were associated with air masses, especially from East China. During the 2013/2014 campaign, the modelled CO from industrial, solvents and agriculture (waste burning on fields) were significantly correlated with the mixing ratios of Cl-VSLS (R > 0.7) and methyl halides (R > 0.40). During the 2015/2016 campaign, the strength of these correlations reduced for Cl-VSLS (R > 0.5) and with no significant correlations for methyl halides. Instead, mixing ratios of methyl halides were correlated (R=0.4) with modelled CO from forest burning. This work provides evidence that East and South East Asia act as important sources of halogenated gases. This is of significant given the proximity of these regions to prevalent deep convection which can rapidly transport these halogen-containing gases into the stratosphere and impact the ozone layer.

Original languageEnglish
Article number012011
JournalIOP Conference Series: Earth and Environmental Science
Volume616
Issue number1
DOIs
Publication statusPublished - 29 Dec 2020
Event2nd International Conference on Green Environmental Engineering and Technology 2020, IConGEET 2020 - Seoul, Virtual, South Korea
Duration: 23 Jul 202024 Jul 2020

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