1. East Asian Emissions of Ozone Depleting Substances Observed in Taiwan
Lauren Gooch, William T. Sturges*, Johannes Laube and David Oram, UEA, UK
Jia-Lin Wang, Cheng-Feng Ou-Yang and Neng-Huei Lin, National Central University, Taiwan
Charles C.-K. Chou, Research Center for Environmental Changes, Academia Sinica, Taiwan
Azizan Abu Samah and Phang Siew-Moi, University of Malaya, Malaysia
*Presenting
Introduction
Whilst the production of many of ozone depleting substances (ODSs) has been phased out or replaced, new threats are emerging; in many cases with unknown origins. Here we present measurements from Taiwan, and also Malaysia (Fig 1), of a range of ‘conventional’ and more recently-discovered ODSs during transport from industrial areas in the wider region. We also note the potential for transport of these ODSs across the South China Sea to the tropics where uplift to the stratosphere is likely.
Sampling and Analysis
Campaigns were carried out in Spring when flow from the N and NE is common (e.g. China, Korea, Japan) alternating with relatively ‘clean’ background air from the West Pacific. Examples of these are shown in the NAME back trajectories plots (Fig 2), as well as an example of local ‘island flow’.
Spring 2013/15
Jan 2014
(1)
Spring 2014
(2)
(3)
Over 60 trace gas species were measured using high sensitivity gas chromatography-mass spectrometry (GC-MS).
Sampling locations in Taiwan and Malaysia
‘AutoSpec’ GC-MS
NAME plots by Dr Matt Ashfold, University of Nottingham Malaysia
Long-range transport to the tropics
HCFC-22 and HFC-23
CFC-113, CFC-113a, and HCFC-133a
CFCs and chlorocarbons
Many ODS abundances are similar to, or occasionally above, those in the ‘background’ atmosphere, suggesting few local or regional sources (e.g. CFC-12, CCl4, CH3CCl3).
Results
Continuing emissions of HCFCs in E. Asia.
Exceptionally elevated very short- lived chlorocarbons (VSLS) – see talk by Oram et al. (QOS )
Whereas CFC-113 is decreasing globally in line with the Montreal Protocol, the recently ‘discovered’ gases CFC-113a and HCFC-133a have increased over the last two decades1,2, from unknown sources.
CFC-113, CFC-113a and HCFC-133a may have common sources or emission regions in E. Asia
They are know to have common origins as intermediates and byproducts in the manufacture of HFC-134a and HFC-125
HFC-23 is a byproduct of the manufacture of HCFC-22.There is some evidence of a weak correlation between the two, but only in 2014 and 2015, with possibly fewer excursions from background in HFC-23 over time.
ODS byproduct species appear to continue to be produced in E.Asia
During the winter monsoon, “cold-surge” events transport emissions from E. Asia south across the South China Sea.
ODS from E. Asia can add to background levels in the tropics during the winter monsoon
See talk by Oram et al. (QOS )
NAME plot by Dr Matt Ashfold, University of Nottingham Malaysia
Evidence for this is seen in elevated levels of some of the aforementioned halocarbons at Bachok on the NE Malaysian coast during Jan/Feb 2014.
typical NH “background’ abundance
typical NH “background’ abundance
typical NH “background’ abundance
typical NH “background’
Halons-1211 and 1202
Halon-1202 is a byproduct of the over-fluorination of HCFC-22 in the manufacture of Halon The two halons are mostly well correlated, with fewer excursions in Halon-1202 in 2015.
There is no evidence from the NAME trajectories of any particular region being associated with their origin.
Others are significantly enhanced, notably HCFCs, CH3Br, and certain chlorocarbons; e.g. CH2Cl2.
All three appear to be well correlated in the Taiwan studies.
typical NH “background’ abundance
typical NH “background’ abundance
References
Laube, et al. Newly detected ozone depleting substances in the atmosphere, Nature Geoscience, 7, 266–269, 2014
Vollmer et al., Abrupt reversal in emissions and atmospheric abundance of HCFC-133a (CF3CH2Cl), Geophys. Res. Lett., 42, 8702–8710, 2015
Conclusions
There is evidence for continuing emissions of certain ODSs from E. Asia in measurements made in Taiwan during 2013/14/15 – notably certain HCFCs, halons, and chlorinated solvents.
Some may be quite specific to E. Asia emissions, e.g. ‘new’ gases such as CFC-113a and HCFC-133a.
Elevated levels of the same gases are seen more than 3,000 km across the South China Sea with CFCs and HCFCs contributing up to an additional 55 ppt of Effective Equivalent Chlorine (EECl) above Northern Hemispheric background; and halons up to 40 ppt more EECl. Chlorocarbons may contribute even more.
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