The gas phase atmospheric photolysis and reactions of key alkyl nitrates and their role in NOy partitioning.

Lead Research Organisation: University of Bristol
Department Name: Chemistry

Abstract

Alkyl nitrates play a crucial role in controlling the budgets of secondary organic aerosols, ozone, NOx, NOy and HOx throughout the troposphere and the importance of these families in determining atmospheric composition, the earth's radiative balance and any future change in climate can not be overemphasised. A number of recent regional and global model studies have demonstrated that vital kinetic and photolytic parameters, especially for the alkyl nitrates formed from the oxidation of biogenic volatile organic compounds, are missing, preventing atmospheric chemical models from describing oxidant chemistry well and hence determining lifetimes of key greenhouse gases and surface pollutants. These kinetic and photolytic parameters include their loss rate via photolysis, loss rate via reaction with OH and O3 and whether NOx is released on reaction with OH and O3. In this study a combination of Turbulent-Flow Chemical Ionisation Mass Spectrometry coupled with a Gas chromatography- electron capture detector (GC-ECD) for the detection of alkyl nitrates will be used to characterise the kinetics of reaction with OH of key alkyl nitrates, whilst a relative rate technique coupled with GC-ECD and GC-MS will be used to characterise the kinetics of reaction of unsaturated organic nitrates with O3 and a state of the art flash photolysis cavity ring system will be used to measure the photolysis and quantum yield of organic nitrates. Such data will be incorporated into models describing the troposphere and compared with available measurements. The proposed work will be crucial to the understanding of the effects of biogenic volatile organic compounds on atmospheric pollution and climate change.

Publications

10 25 50

 
Description Organic nitrates in the atmosphere are formed through the reaction of organic free radicals and nitrogen oxides (NOx). It emerges that in natural environments naturally occurring free radicals assist terrestrial plants in particular by sequestering NOx formed by soil bacteria that are released into the atmosphere. Once formed these organic nitrates can be deposited to the surface and provide much needed nitrogen to the plant. However, in polluted environments these organic nitrates can store NOx and release it later on in an air masses history leading to ozone formation. In this study we have been able to characterise a number of organic nitrates and their chemical reactivity so that we can determine whether they are likely to deposit (good) or assist on ozone formation (bad).
Exploitation Route We are generating data for updates to the MCM (Master Chemical Mechanism) so that these data can be used more widely
Sectors Environment,Transport

 
Description Examples in science teaching in UK secondary schools
First Year Of Impact 2014
Sector Education
 
Description Leverhulme Grant Scheme
Amount £186,000 (GBP)
Organisation The Leverhulme Trust 
Sector Academic/University
Country United Kingdom
Start 02/2014 
End 02/2017
 
Description Please look at http://www.chemlabs.bris.ac.uk/outreach/latest.html this details the myriad outreach work that we do 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Schools
Results and Impact We run numerous Outreach activities please refer to the website log.

Please read our education papers
1. Criegee Biradicals and Climate Change. D.E. Shallcross and T.G. Harrison. Education in Chemistry 50(5) 22-24, 2013
2. Creating Climate Change Awareness in South African Schools Through Practical Chemistry Demonstrations. Suthananda N Sunassee, Ryan M Young, Joyce D Sewry, Timothy G Harrison, Dudley E Shallcross. Acta Didactica Napocensia 4, 35-48 (2012).
3. Outreach within the Bristol ChemLabS CETL (Centre for Excellence in Teaching and Learning). D.E. Shallcross, T.G. Harrison, T.M. Obey, S.J. Croker, N.C. Norman. Higher Education Studies 3(1), 39-49, 2013
4.
Year(s) Of Engagement Activity Pre-2006,2006,2007,2008,
URL http://www.chemlabs.bris.ac.uk/outreach/latest.html