Reducing uncertainties in Ozone formation via Chamber Studies of VOC Oxidation
Lead Research Organisation:
University of Leeds
Department Name: Sch of Chemistry
Abstract
Chambers are a vital tool in understanding the chemistry of our atmosphere. They are an ideal vehicle to test proposed mechanisms under simplified, controlled but realistic conditions. The HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry) chamber was constructed during grant NE/C513493/1 and contains several significant features: 1) Uniquely, for an indoor chamber, we can monitor OH and HO2 radicals directly using the FAGE technique. 2) As the chamber is of a stainless steel construction, it is possible to vary pressures over tropospherically relevant conditions. 3) Many important species can be measured by a variety of techniques. This allows us to investigate the possibility of systematic measurement errors. Concentrations of tropospheric ozone are predicted to rise with implications for climate change and air quality. The current proposal seeks to study a number of reactions that are important in determining ozone levels. The mechanims are complex and can only be unravelled via experimental measurements. HIRAC, with a range of complementary detection systems, is an ideal tool to tackle these systems. The reactions to be studied are: 1) Ozone/alkene reactions have been shown to be an important source of OH radicals especially at night. We propose to measure OH and co-product yields as a function of alkene structure in order to construct temperature and pressure dependent structure activity relationships. 2) OH + aromatics - The peroxy radical formed from the attack of OH on the aromatic ring and addition of O2 can react via two channels, either generating a phenol + HO2 (radical regeneration) or ring opening to give dicarbonyl species which are important radical and aerosol precursors. The branching ratio for peroxy radicals formed from reaction of OH with benzene and toluene will be investigated, supported by ab initio calculations. 3) Recent work in our laboratory has identified significant fragmentation of the CH3CO radical formed from OH abstraction of ethanal. If confirmed, this would have important implications for PAN formation. Modelling simulations shown that monitoring CO and CO2 yields should confirm the presence or absence of chemically activated acetyl decomposition under atmospheric conditions. 4) OH + alkynes. The reaction with OH is the major atmospheric removal process for acetylene, an abundant anthropogenic and biomass pollutant. In the prescence of O2, there are two product channels generating glyoxal/OH and HCOOH/HCO. Glyoxal can be photolysed at relatively long wavelengths to give 2HCO radicals and is hence an important HOx source but, being relatively involatile, is also known to be a good aerosol precursor. The atmospheric budget of formic acid is poorly constrained. 5) OH + alkenes. Ethene oxidation is the single largest contributor to European O3 formation. The major uncertainties in this reaction is the rate of reaction of the intially formed hydroxyperoxy radical with NO and the fate of the product alkoxy radical. Both issues can be addressed by product studies in HIRAC As part of the proposal temperature control will be provided for HIRAC to simulate all conditions of the troposphere. One element of the study will be a systematic study (through a tied studentship) of a range of OH, Cl and NO3 reactions via relative and absolute techniques to construct temperature dependent structure activity relationships (SAR). Such SAR are vital in the development of the MCM for temperature dependent modelling of O3 formation and other issues.
Organisations
Publications
Carr SA
(2011)
Experimental and modeling studies of the pressure and temperature dependences of the kinetics and the OH yields in the acetyl + O2 reaction.
in The journal of physical chemistry. A
Farrugia L
(2015)
Revised structure activity parameters derived from new rate coefficient determinations for the reactions of chlorine atoms with a series of seven ketones at 290 K and 1 atm
in Chemical Physics Letters
Glowacki DR
(2012)
Interception of excited vibrational quantum states by O2 in atmospheric association reactions.
in Science (New York, N.Y.)
Lockhart J
(2013)
Mechanism of the reaction of OH with alkynes in the presence of oxygen.
in The journal of physical chemistry. A
Malkin T
(2010)
Measurements of OH and HO<sub>2</sub> yields from the gas phase ozonolysis of isoprene
in Atmospheric Chemistry and Physics
Seakins P
(2010)
A brief review of the use of environmental chambers for gas phase studies of kinetics, chemical mechanisms and characterisation of field instruments
in EPJ Web of Conferences
Seakins PW
(2011)
Developments in laboratory studies of gas-phase reactions for atmospheric chemistry with applications to isoprene oxidation and carbonyl chemistry.
in Annual review of physical chemistry
Whalley L
(2013)
Reporting the sensitivity of laser-induced fluorescence instruments used for HO<sub>2</sub> detection to an interference from RO<sub>2</sub> radicals and introducing a novel approach that enables HO<sub>2</sub> and certain RO<sub>2</sub> types to be selectively measured
in Atmospheric Measurement Techniques
Description | This project focused at looking at key reactions that contributed to the generation of O3 (a harmful pollutant and contributor to global warming) in the troposphere. The project utilized an advanced atmospheric chamber and an initial component of the project was to install a new laser system for OH and HO2 (key atmospheric intermediates) detection and to make the chamber temperature controllable. Following the instrumental upgrades we have successfully examined the following relevant reaction systems: O3 + isoprene, looking at OH and HO2 detection OH + alkyne reactions OH + acetaldehyde. Additionally we have also developed a new method for pressure dependent calibration of OH and HO2 detection. |
Exploitation Route | Explotation has been through academic publications and conference presentations. Two publications and 3 PhD thesis have been published. A further publication has been accepted in ACP. |
Sectors | Environment |
URL | http://www.chem.leeds.ac.uk/HIRAC/ |
Description | Work performed as part of this project has enhanced our understanding of ozone reactions in the troposphere and of oxidative chemistry in general. Outputs from the project have been included in the master chemical mechanism (MCM) which is an important tool linking to policy (e.g. modelling ozone forming potentials). Ozone formation links strongly to air quality (and hence health) and also contributes significantly to radiative forcing. |
First Year Of Impact | 2011 |
Sector | Environment |
Impact Types | Policy & public services |
Description | EUROCHAMP 2020 |
Amount | £3,000,000 (GBP) |
Funding ID | 730997 |
Organisation | European Commission |
Department | Horizon 2020 |
Sector | Public |
Country | European Union (EU) |
Start | 12/2016 |
End | 12/2020 |
Description | Equipment Grant associated with BioEnergy CDT at University of Leeds |
Amount | £110,000 (GBP) |
Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
Sector | Public |
Country | United Kingdom |
Start | 11/2014 |
End | 06/2015 |
Description | Marie Curie Fellowship Award |
Amount | £300,000 (GBP) |
Organisation | European Commission |
Sector | Public |
Country | European Union (EU) |
Start | 06/2013 |
End | 06/2015 |
Description | EUROCHAMP Activity |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Participants in your research and patient groups |
Results and Impact | Outreach and collaboration with other researchers across Europe. Hosted visitors from Germany and Spain. Publications and research collaborations |
Year(s) Of Engagement Activity | 2012,2013,2014 |