After 2012, emissions of dichloromethane from China accounted for 50–60 per cent of the global total
Emissions of industrially produced chlorocarbon, dichloromethane (CH2Cl2), increased in China from 2011-2019, a new study established. The emissions grew to 628 gigagrams (Gg) per year in 2019 from 231 Gg per year in 2011 in the country, with an average annual increase of 13 per cent primarily from eastern China.
The overall increase in CH2Cl2 emissions from China has the same magnitude as the global emission rise of 354 Gg per year over the same period.
If global dichloromethane emissions remain at 2019 levels, they could lead to a delay of around five years in Antarctic ozone recovery compared to a scenario with no dichloromethane emissions, the report published in Nature Communications noted.
Short-lived halogenated substances (VSLS) such as dichloromethane have an atmospheric lifetime shorter than six months. Dichloromethane has been identified as the most abundant chlorine-containing VSLS, accounting for 70 per cent of the total stratospheric source gas injection from chlorine-containing VSLS.
Dichloromethane originates mainly from anthropogenic sources, including its use as an emissive solvent for adhesive and cleaning purposes, and as a feedstock for hydrofluorocarbon (HFC) production.
Luke Western from the School of Chemistry, University of Bristol said:
International monitoring networks have known that global atmospheric concentrations of dichloromethane have been rising rapidly over the last decade, but until now, it was unclear what was driving the increase.
To answer that question researchers from Peking University, the China Meteorological Administration and the University of Bristol teamed up to examine new data collected within China.
A substantial increase in the annual dichloromethane emissions from China in 2011-2019 was observed using measurements from nine sites within China Meteorological Administration’s monitoring network by an inverse modelling approach.
The mean annual emissions growth rate in China was 13 per cent. There was a rapid increase in emissions after 2012, from 272 Gg per year in 2012 to 534 Gg per year in 2015. After 2015, emissions continued to rise overall but at a much slower rate.
China accounted for 30-35 per cent of global dichloromethane emissions in 2011-2012. After 2012, emissions from China accounted for 50–60 per cent of the global total.
The eastern part of China, including part of the North China Plain and the Yangtze River Delta region, are shown to be the main source regions for dichloromethane over the study period. These regions also contribute most to the increase between the pre-2012 and post 2015 periods. The Yangtze River Delta region, which consists of the highly populated provinces Zhejiang, Jiangsu, Shanghai and Anhui, was one of the biggest emitters.
Most chloromethane factories in China are in Shandong province, the Yangtze River Delta and the Sichuan Basin, which is consistent with the key regions that exhibit high emissions and emission increase in this study.
The main regions of dichloromethane emissions in China and their increase over the study period are highly consistent with the locations of economically developed and industrialised regions, confirming a substantial anthropogenic source for emissions in China.
The increase in emissions from China plays an important role in the global emissions growth, and these increases have the potential to impact the recovery of the stratospheric ozone layer.
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