Production and removal of tropospheric oxidants
Halogen oxide kinetics and photochemistry
Iodine species in the atmosphere
Current / recent research
Radical Production from Alkene Ozonolysis
The gas-phase reaction between ozone and alkenes produces a range of products, including radical species which contribute to atmospheric oxidation, and partially oxidised organic compounds which add to atmospheric reactivity. This project aims to investigate the radical and organic gas-phase products formed from the ozonolysis of a range of alkenes of biogenic and anthropogenic origin. The experimental work is being performed using the European Photoreactor (EUPHORE) simulation chamber, in Valencia, Spain. This project is funded by NERC in collaboration with Prof Paul Monks (Leicester) and Dr Andrew Rickard (Leeds), and is being conducted by Salim Alam and Dr Marie Camredon.
Impacts of Aerosol upon Atmospheric Oxidants
Atmospheric oxidants, gas-phase species such as OH and HO2, drive the removal of most pollutants, limit the levels of global warming gases such as methane, and initiate the formation of low-level ozone. Understanding their abundance is central to predicting future atmospheric composition. The oxidant species can be removed from the atmosphere by reaction with aerosol (condensed material), reducing their concentrations, and oxidising the condensed phase components altering their properties. Calculations show that these reactions can have a major impact upon oxidant levels and aerosol evolution, but details of the processes are poorly understood. This project uses a laboratory flow-tube system to study the interaction of gas-phase radical species with various atmospheric aerosol, and is being carried out by Kate Faloon and Suad Al-Kindi.
Point Measurements of Iodine and Bromine in the Marine Boundary Layer
Halogen species, particularly iodine and bromine compounds, are released from the ocean surface by marine organisms and through inorganic mechanisms. In the atmosphere, these compounds are photolysed, releasing the halogen atoms (I or Br), which can then influence atmospheric oxidant levels, participate in catalytic ozone destruction cycles and potentially lead to the formation of new atmospheric particles. These processes are known to occur in certain coastal regions, but their significance over the open ocean, and hence overall global impact, is uncertain: this project aims to address this uncertainty, through development of a new technique to perform point measurements of halogen atoms in the atmosphere. This work is being conducted by Dr Juan Najera.
Stratospheric Halogen Photochemistry
The stratospheric ozone layer protects the planet’s biosphere from harmful solar UV radiation, determines the temperature structure and hence circulation of the middle atmosphere, and contributes to radiative balance. The chemical mechanism for formation of the ozone hole involves the photolysis of the ClO dimer, Cl2O2, as a rate limiting step. Uncertainty over the photochemistry of Cl2O2 is one of the major limitations in our current understanding of the chemical causes of ozone depletion. In this project, we aim to apply UV absorption spectroscopy, resonance fluorescence and chemical ionisation mass spectrometry approaches to improve our understanding of Cl2O2 photolysis. This project is funded by NERC in collaboration with Dr Carl Percival from the University of Manchester, and is being carried out by Dr Shana Saha.
Key Publications since 2001
W.J. Bloss, M. Camredon, J. D. Lee, D. E. Heard, J. M. C. Plane, A. Saiz-Lopez, S. J.-B. Bauguitte, R. A. Salmon, and A. E. Jones (2010) Coupling of HOx, NOx and halogen chemistry in the Antarctic boundary layer, Atmos. Chem. Phys., 10, 10187-10209, 2010.
A. K. Mollner, L. Feng, M. K. Sprague, M. Okumura, D. B. Milligan, W. J. Bloss, S. P. Sander, P. T. Martien, R. A. Harley, A. B. McCoy and W.P. Carter (2010) Rate of gas phase association of hydroxyl radical and nitrogen dioxide, Science, 330, 646-649, 2010.
M. Camredon, J. F. Hamilton, M. S. Alam, K. P. Wyche, T. Carr, I. R. White, P. S. Monks, A. R. Rickard, and W. J. Bloss (2010) Distribution of gaseous and particulate organic composition during dark α-pinene ozonolysis, Atmos. Chem. Phys. 10, 2893-2917
C.S.E. Bale, T. Ingham, R. Commane, D.E. Heard and W.J. Bloss (2008) Novel Measurements of atmospheric iodine species by resonance fluorescence, J. Atmos. Chem. 60, 51-70 (2008) Novel Measurements of atmospheric iodine species by resonance fluorescence,. 60, 51-70
W.J. Bloss, J.D. Lee, D.E. Heard, R.A. Salmon, S. J.-B. Bauguitte, H.K. Roscoe and A.E. Jones (2007) Observations of OH and HO2 Radicals in coastal Antarctica. Atmos. Chem. Phys. 7, 4171-4185
W.J. Bloss, M.J. Evans, R. Sommariva, D.E. Heard, M.J. Pilling (2005) The oxidative capacity of the troposphere: Coupling of field measurements of OH and a global chemistry transport model. Faraday Discuss. 130, 425-436.
W.J. Bloss, J.D. Lee, G.P. Johnson, D.E. Heard, R. Sommariva, J.M.C. Plane, A. Saiz-Lopez, G. McFiggans, H. Coe, M. Flynn, P. Williams, A. Rickard and Z. Fleming (2005) Impact of Halogen Monoxide Chemistry upon Boundary Layer OH and HO2 concentrations at a Coastal Site. Geophys. Res. Lett. 32, doi:10.1029/2004GL022084.
W.J. Bloss, S.N. Nickolaisen, R.J. Salawitch, R.R. Friedl and S.P. Sander (2001) Kinetics of the ClO Self-Reaction and 210 nm Absorption Cross Section of the ClO Dimer. J. Phys. Chem. A, 105, 11226-11239.
W.J. Bloss, D.M. Rowley, R.A. Cox and R.L. Jones (2001) Kinetics and Products of the IO Self-Reaction. J. Phys. Chem. A, 105, 7840-7854