Source of large rise in emissions of unregulated ozone destroying
substance identified

Date:
December 14, 2021
Source:
University of Bristol
Summary:
New research has discovered that emissions coming from China of
the ozone-destroying chemical, dichloromethane, have more than
doubled over the last decade.



FULL STORY ==========================================================================
New research, led by the University of Bristol and Peking University,
has discovered that emissions coming from China of the ozone-destroying chemical, dichloromethane, have more than doubled over the last decade.


========================================================================== Since the signing of the Montreal Protocol, there has been a dramatic drop
in emissions of the main substances that are responsible for depleting
the stratospheric ozone layer, the part of the atmosphere that protects
us from harmful solar radiation.

Compared to the CFCs, and other regulated ozone-destroying compounds, dichloromethane only lasts for a short time in the atmosphere -- around
six months. Mainly for this reason, its production and use hasn't been controlled under the Montreal Protocol in the same way as longer-lived ozone-depleting substances.

Dr Luke Western from the University of Bristol's School of Chemistry,
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. Their results are published today in the journal Nature Communications.

Minde An, a postgraduate student from Peking University, and visiting researcher at the University of Bristol led the study.



==========================================================================
He said: "China is an important producer and user of compounds such as dichloromethane. Therefore, we wanted to examine measurements within
the country to determine its contribution to global emissions.

"Our calculations revealed that China's share of total global emissions
grew from about one-third to two-thirds over the last decade. The global emissions increase since 2011 is the same size as the rise in emissions
from China.

"We think that emissions of dichloromethane from China have increased
because of its use as a solvent in various industrial applications and
the expanding chloromethanes industry in China." Current controls on the
use of dichloromethane in China only relate to its toxicity or its role
in causing urban air pollution. Levels of dichloromethane are regulated
in consumer products, and there are restrictions on release rates from industrial processes, but there is no control on the overall amount that
can be emitted to the atmosphere.

Historically, emission rates of dichloromethane have been small enough
to not overly worry researchers studying ozone layer recovery. However,
the recent rise needs to be carefully watched in future.



==========================================================================
Dr Ryan Hossaini from the University of Lancaster, and co-author of the
study, said: "If current levels of dichloromethane persist, we could
expect to see a delay in ozone layer recovery of a few years. However,
if they continue to grow at the rate we've seen over the last decade,
it could lead to a delay of over a decade, though future emissions are
highly uncertain.

"Of significance is the location of the emissions discovered in this
study.

Short-lived compounds like dichloromethane are partly destroyed in the
lower atmosphere before they reach the ozone layer.

"However, in some parts of Asia, there are regions where the
atmosphere can transport these substances to the stratosphere relatively quickly. This means emissions from these regions may pack a bigger punch
than those released elsewhere." Despite these concerns, there are signs
that changes may be coming. In the last month, draft regulation by the
Ministry of Ecology and Environment in China listed dichloromethane as
a new pollutant whose use in several sectors such as paint stripping or insulating foam production could be banned.

Professor Matt Rigby, also from the University of Bristol's School
of Chemistry, said he was hopeful that these results can be repeated
in the future to determine the impact of changes in regulation for dichloromethane and other compounds of interest to the Montreal Protocol.

He added: "One of the most important outcomes of this work is
in showing what can be achieved through the close collaboration
between scientists from around the world." "These measurements
from China are highly valuable for researchers and policymakers
who are interested in the ozone layer and climate. We're looking
forward to continuing this work in future, to provide the parties
to the Montreal Protocol with increasingly accurate information
to help ensure that the recovery of the ozone layer stays on track." ========================================================================== Story Source: Materials provided by University_of_Bristol. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Minde An, Luke M. Western, Daniel Say, Liqu Chen, Tom Claxton,
Anita L.

Ganesan, Ryan Hossaini, Paul B. Krummel, Alistair J. Manning,
Jens Mu"hle, Simon O'Doherty, Ronald G. Prinn, Ray F. Weiss,
Dickon Young, Jianxin Hu, Bo Yao, Matthew Rigby. Rapid increase
in dichloromethane emissions from China inferred through
atmospheric observations. Nature Communications, 2021; 12 (1)
DOI: 10.1038/s41467-021-27592-y ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211214084533.htm

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