Abstract
Carbon tetrachloride (CCl4) is an ozone-depleting substance, accounting for about 10% of the chlorine in the troposphere. Under the terms of the Montreal Protocol, its production for dispersive uses was banned from 2010. In this work we show that, despite the controls on production being introduced, CCl4 emissions from the eastern part of China did not decline between 2009 and 2016. This finding is in contrast to a recent bottom-up estimate, which predicted a significant decrease in emissions after the introduction of production controls. We find eastern Asian emissions of CCl4 to be 16 (9–24) Gg/year on average between 2009 and 2016, with the primary source regions being in eastern China. The spatial distribution of emissions that we derive suggests that the source distribution of CCl4 in China changed during the 8-year study period, indicating a new source or sources of emissions from China’s Shandong province after 2012.
Highlights
Carbon tetrachloride (CCl4) was historically used as a solvent, cleaning agent, and as a feedstock in the production of other compounds such as the chlorofluorocarbons (CFCs; Carpenter et al, 2014)
We find eastern Asian emissions of CCl4 to be 16 (9–24) Gg/year on average between 2009 and 2016, with the primary source regions being in eastern China
The spatial distribution of emissions that we derive suggests that the source distribution of CCl4 in China changed during the 8-year study period, indicating a new source or sources of emissions from China’s Shandong province after 2012
Summary
Carbon tetrachloride (CCl4) was historically used as a solvent, cleaning agent, and as a feedstock in the production of other compounds such as the chlorofluorocarbons (CFCs; Carpenter et al, 2014). We follow an inverse modeling approach, where 8 years of near-continuous CCl4 data are used from the Advanced Global Atmospheric Gases Experiment (AGAGE; Prinn et al, 2018) station at Gosan, South Korea. These data are used in conjunction with two atmospheric transport models, the Numerical Atmospheric dispersion Modelling Environment (NAME; Jones et al, 2007; Manning et al, 2011) and the FLEXible PARTicle dispersion model (FLEXPART; Stohl et al, 2005), and two different statistical methods to investigate the magnitude and spatial distribution of emissions from the region of eastern Asia surrounding Gosan between 2009 and 2016. Significant changes in emissions may be expected during this period, given the Montreal Protocol phaseout schedule
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