Changes to the chemical state of the Northern Hemisphere atmosphere during the second half of the twentieth century

Newland, Michael J., Martinerie, Patricia, Witrant, Emmanuel, Helmig, Detlev, Worton, David R., Hogan, Christopher, Sturges, William T. ORCID: https://orcid.org/0000-0002-9044-7169 and Reeves, Claire E. ORCID: https://orcid.org/0000-0003-4071-1926 (2017) Changes to the chemical state of the Northern Hemisphere atmosphere during the second half of the twentieth century. Atmospheric Chemistry and Physics, 17 (13). 8269–8283. ISSN 1680-7324

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Abstract

The NOx (NO and NO2) and HOx (OH and HO2) budgets of the atmosphere exert a major influence on atmospheric composition, controlling removal of primary pollutants and formation of a wide range of secondary products, including ozone, that can influence human health and climate. However, there remain large uncertainties in the changes to these budgets over recent decades. Due to their short atmospheric lifetimes, NOx and HOx are highly variable in space and time, and so the measurements of these species are of limited value for examining long-term, large-scale changes to their budgets. Here, we take an alternative approach by examining long-term atmospheric trends of alkyl nitrates, the production efficiency of which is dependent on the atmospheric [NO] ∕ [HO2] ratio. We derive long-term trends in the alkyl nitrates from measurements in firn air from the NEEM site, Greenland. Their mixing ratios increased by a factor of 3–5 between the 1970s and 1990s. This was followed by a steep decline to the sampling date of 2008. Moreover, we examine how the trends in the alkyl nitrates compare to similarly derived trends in their parent alkanes (i.e. the alkanes which, when oxidised in the presence of NOx, lead to the formation of the alkyl nitrates). The ratios of the alkyl nitrates to their parent alkanes increased from around 1970 to the late 1990s. This is consistent with large changes to the [NO] ∕ [HO2] ratio in the Northern Hemisphere atmosphere during this period. Alternatively, they could represent changes to concentrations of the hydroxyl radical, OH, or to the transport time of the air masses from source regions to the Arctic.

Item Type:	Article
Uncontrolled Keywords:	sdg 3 - good health and well-being,sdg 13 - climate action ,/dk/atira/pure/sustainabledevelopmentgoals/good_health_and_well_being
Faculty \ School:	Faculty of Science > School of Environmental Sciences University of East Anglia Research Groups/Centres > Theme - ClimateUEA
UEA Research Groups:	Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences Faculty of Science > Research Groups > Marine and Atmospheric Sciences (former - to 2017) Faculty of Science > Research Groups > Atmospheric Chemistry (former - to 2018) Faculty of Science > Research Groups > Climate, Ocean and Atmospheric Sciences (former - to 2017)
Depositing User:	Pure Connector
Date Deposited:	08 Jul 2017 05:05
Last Modified:	20 Mar 2023 09:37
URI:	https://ueaeprints.uea.ac.uk/id/eprint/64063
DOI:	10.5194/acp-17-8269-2017

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