Fundamental chemical processes controlling tropospheric composition and change
The Earth’s atmosphere is a hugely complex, multi-phase system, the chemistry of which is controlled by tiny quantities of reactive species, including oxides of nitrogen, ozone, and volatile organic compounds. These trace species, and their tropospheric chemistry lie at the heart of many of our contemporary environmental and air quality issues, including summertime smog and particle formation. In order to better understand the roles and impacts of such reactive species within the Earth’s atmosphere, we have been using environment chambers and chemical modelling to simulate and study their reaction mechanisms. The primary focus of our research in this area is the atmospheric oxidation of volatile organic compounds and their partitioning to the particle phase to form Secondary Organic Aerosol (SOA).
Projects
The AER team has, and continues to, work on numerous collaborative projects in the area of Tropospheric Composition and Change; click on the links below to find out more about each piece of work:
Mass Spectrometers for the CHemical Analysis of Organic aerosolS (MSCHAOS)
Aerosol Coupling in the Earth System (ACES)
Total Radical Production and Degradation Products from Alkene Ozonolysis (TRAPOZ)
Toluene OXidation In a Chamber (TOXIC)
Highlight article
“Mapping gas-phase organic reactivity and concomitant secondary organic aerosol formation: chemometric dimension reduction techniques for the deconvolution of complex atmospheric data sets” Wyche et al., Atmospheric Chemistry and Physics, 2015, 15. pp. 8077-8100. ISSN 1680-7316
Read More…
Highly non-linear dynamical systems, such as those found in atmospheric chemistry, necessitate hierarchical approaches to both experiment and modeling in order, ultimately, to identify and achieve fundamental process-understanding in the full open system. Atmospheric simulation chambers comprise an intermediate in complexity, between a classical laboratory experiment and the full, ambient system. As such, they can generate large volumes of difficult-to-interpret data. Here we describe and implement a chemometric dimension reduction methodology for the deconvolution and interpretation of complex gas- and particle-phase composition spectra. The methodology comprises principal component analysis (PCA), hierarchical cluster analysis (HCA) and positive least squares-discriminant analysis (PLS-DA). These methods are, for the first time, applied to simultaneous gas- and particle-phase composition data obtained from a comprehensive series of environmental simulation chamber experiments focused on biogenic volatile organic compound (BVOC) photooxidation and associated secondary organic aerosol (SOA) formation. We primarily investigated the biogenic SOA precursors isoprene, α-pinene, limonene, myrcene, linalool and β-caryophyllene. The chemometric analysis is used to classify the oxidation systems and resultant SOA according to the controlling chemistry and the products formed. Furthermore, a holistic view of results across both the gas- and particle-phases shows the different SOA formation chemistry, initiating in the gas-phase, proceeding to govern the differences between the various BVOC SOA compositions. The results obtained are used to describe the particle composition in the context of the oxidized gas-phase matrix. An extension of the technique, which incorporates into the statistical models data from anthropogenic (i.e. toluene) oxidation and “more realistic” plant mesocosm systems, demonstrates that such an ensemble of chemometric mapping has the potential to be used for the classification of more complex spectra of unknown origin. The potential to extend the methodology to the analysis of ambient air is discussed using results obtained from a zero-dimensional box model incorporating mechanistic data obtained from the Master Chemical Mechanism (MCMv3.2). Such an extension to analysing ambient air would prove a powerful asset in assisting with the identification of SOA sources and the elucidation of the underlying chemical mechanisms involved.
Collaborators
Mediterranean Center for Environmental Studies, ES
Funders
Natural Environment Research Council (NERC)
Engineering and Physical Sciences Research Council (EPSRC)
Atmospheric Composition Change. The European NeTwork for excellence (ACCENT)
Integration of European Simulation Chambers for Investigating Atmospheric Processes (EUROCHAMP)
Research Outputs
Pereira, Kelly L., Hamilton, J.F., Rickard, A.R., Bloss, W.J., Alam, M.S., Camredon, M., Ward, M.W., Wyche, Kevin, Munoz, Amalia, Vera, Teresa, Vazquez, Monica, Borras, Esther and Rodenas, Milagros (2015) Insights into the Formation and Evolution of Individual Compounds in the Particulate Phase during Aromatic Photo-Oxidation Environmental Science and Technology, 49 (22). pp. 13168-13178. ISSN 0013-936X
Wyche, Kevin, Monks, P.S., Smallbone, Kirsty, Hamilton, J.F., Alfarra, M.R., Rickard, A.R., McFiggans, G.B., Jenkin, M.E., Bloss, W.J., Ryan, A.C., Hewitt, C.N. and MacKenzie, A.R. (2015) Mapping gas-phase organic reactivity and concomitant secondary organic aerosol formation: chemometric dimension reduction techniques for the deconvolution of complex atmospheric data sets Atmospheric Chemistry and Physics, 15. pp. 8077-8100. ISSN 1680-7316
Wyche, Kevin, Ryan, A.C., Hewitt, C.N., Alfarra, M.R., McFiggans, G.B., Carr, T., Monks, P.S., Smallbone, Kirsty, Capes, G., Hamilton, J.F., Pugh, T.A.M. and MacKenzie, A.R. (2014) Emissions of biogenic volatile organic compounds and subsequent photochemical production of secondary organic aerosol in mesocosm studies of temperate and tropical plant species Atmospheric Chemistry and Physics, 14. pp. 12781-12801. ISSN 1680-7316
Bloss, W.J., Alam, M.S., Rickard, A.R., Camredon, M., Wyche, Kevin, Carr, T. and Monks, P.S. (2013) Production of the Atmospheric Oxidant Radicals OH and HO2 from the Ozonolysis of Alkenes In: Barnes, I. and Rudziński, K.J., eds. Disposal of Dangerous Chemicals in Urban Areas and Mega Cities: Role of Oxides and Acids of Nitrogen in Atmospheric Chemistry. Springer, Netherlands, pp. 151-162. ISBN 9789400750333
Alfarra, M.R., Good, N., Wyche, Kevin, Hamilton, J.F., Monks, P.S., Lewis, A.C. and McFiggans, G.B. (2013) Water uptake is independent of the inferred composition of secondary aerosols derived from multiple biogenic VOCs Atmospheric Chemistry and Physics, 13 (23). pp. 11769-11789. ISSN 1680-7316
Alam, M.S., Rickard, A.R., Camredon, M., Wyche, Kevin, Carr, T., Hornsby, K.E., Monks, P.S. and Bloss, W.J. (2013) Radical Product Yields from the Ozonolysis of Short Chain Alkenes under Atmospheric Boundary Layer Conditions Journal of Physical Chemistry A, 117 (47). pp. 12468-12483. ISSN 1089-5639
Alfarra, M.R., Hamilton, J.F., Wyche, Kevin, Good, N., Ward, M.W., Carr, T., Barley, M.H., Monks, P.S., Jenkin, M.E., Lewis, A.C. and McFiggans, G.B. (2012) The effect of photochemical ageing and initial precursor concentration on the composition and hygroscopic properties of β-caryophyllene secondary organic aerosol Atmospheric Chemistry and Physics, 12 (14). pp. 6417-6436. ISSN 1680-7316
Jenkin, M.E., Wyche, Kevin, Evans, C.J., Carr, T., Monks, P.S., Alfarra, M.R., Barley, M.H., McFiggans, G.B., Young, J.C. and Rickard, A.R. (2012) Development and chamber evaluation of the MCM v3.2 degradation scheme for beta-caryophyllene Atmospheric Chemistry and Physics, 12 (11). pp. 5275-5306. ISSN 1680-7316
Hamilton, J.F., Alfarra, M.R., Wyche, Kevin, Ward, M.W., Lewis, A.C., McFiggans, G.B., Good, N., Monks, P.S., Carr, T., White, I.R. and Purvis, R.M. (2011) Investigating the use of secondary organic aerosol as seed particles in simulation chamber experiments Atmospheric Chemistry and Physics, 11 (12). pp. 5917-5929. ISSN 1680-7316
Alam, M.S., Camredon, M., Rickard, A.R., Carr, T., Wyche, Kevin, Hornsby, K.E., Monks, P.S. and Bloss, W.J. (2011) Total radical yields from tropospheric ethene ozonolysis Physical Chemistry Chemical Physics, 13 (23). pp. 11002-11015. ISSN 1463-9076
Rickard, A.R., Wyche, Kevin, Metzger, A., Monks, P.S., Ellis, A.M., Dommen, J., Baltensperger, U., Jenkin, M.E. and Pilling, M.J. (2010) Gas phase precursors to anthropogenic secondary organic aerosol: using the Master Chemical Mechanism to probe detailed observations of 1,3,5-trimethylbenzene photo-oxidation Atmospheric Environment, 44 (40). pp. 5423-5433. ISSN 0004-6981
Wyche, Kevin, Edwards, A.G., Monks, P.S., Leigh, R. and Davies, E. (2010) How clean is our air? Local air quality monitoring and a role for GMES
Camredon, M., Hamilton, J.F., Alam, M.S., Wyche, Kevin, Carr, T., White, I.R., Monks, P.S., Rickard, A.R. and Bloss, W.J. (2010) Distribution of gaseous and particulate organic composition during dark α-pinene ozonolysis Atmospheric Chemistry and Physics, 10 (6). pp. 2893-2917. ISSN 1680-7316
Parker, A.E., Monks, P.S., Wyche, Kevin, Balzani-LÃuÃv, J.M., Staehelin, J., Reimann, S., Legreid, G., Vollmer, M.K. and Steinbacher, M. (2009) Peroxy radicals in the summer free troposphere: seasonality and potential for heterogeneous loss Atmospheric Chemistry and Physics, 9 (6). pp. 1989-2006. ISSN 1680-7316
Wyche, Kevin, Monks, P.S., Ellis, A.M., Cordell, R.L., Parker, A.E., Whyte, C., Metzger, A., Dommen, J., Duplissy, J., Prevot, A.S.H., Baltensperger, U., Rickard, A.R. and Wulfert, F. (2009) Gas phase precursors to anthropogenic secondary organic aerosol: detailed observations of 1,3,5-trimethylbenzene photooxidation Atmospheric Chemistry and Physics, 9 (2). pp. 635-665. ISSN 1680-7316