ClearfLo - London(2012)
Urban pollution such as that currently endured in London has an adverse effect on human health.
However, an understanding of the chemical processes responsible for such poor air quality is incomplete.
The Clean Air for London (ClearfLo) campaign in Jan/Feb 2012 and July/August 2012 aims to deliver a
comprehensive range of atmospheric measurements across London at both ground based and elevated sites.
These observations complemented by modelling will be used in an effort to improve predictive capability for air
quality in London. The main aims and objectives of ClearfLo with respect to radical species are to measure such
species concurrent with their sources and sinks and to quantify the oxidative budget of London’s urban atmosphere both in winter and in summer.
The University of Leeds is responsible for measurements of gas phase radicals (i.e. OH, HO2 and RO2).
The comprehensive suite of field measurements planned during the ClearfLo campaigns will be followed by a detailed synthesis of the
winter and summer datasets to enable the oxidative budget of the winter and summer atmospheres to be determined.
These field observations will be used to constrain a detailed zero-dimensional model based on the Master Chemical Mechanism
and the model will be used to calculate the oxidative budget of London’s urban atmosphere.
Further information can be found at http://www.clearflo.ac.uk/
Hill Cap Cloud Thuringia (HCCT) - Germany (2010)
The ground based FAGE instrument took part in the HCCT-2010 campaign, which ran from the 13th September until 24th October 2010.
The project is funded by the Leibniz-Institut fur Tropospharenforschung (IFT) and involves collaboration with a number
of international partners.
Clouds play a crucial role in the chemistry of the atmosphere, occupying, on average ~ 15 % of the volume of the lower
atmosphere. Modelling studies have shown that aqueous phase chemistry in clouds can influence
gas phase radical chemistry and in turn can cause significant reductions in the oxidative capacity. The HCCT project aims to
quantify the uptake of OH and HO2 radicals in cloud droplets and
to study the dependency of this uptake efficiency on the different microphysical and chemical conditions encountered during
different cloud events. The instrument was located at Mt. Schmucke, Thuringia in Germany; a site where hill cap
clouds frequently occur. The photograph shows the FAGE instrument measuring during a cloud event; the detection cell is
co-located at the top of the 22 m tower alongside cloud water samplers and other instrumentation.
Analysis of the measurements made during the campaign are underway.
Seasonal Oxidant Study (SOS) - Cape Verde (2009)
In 2009 the AirFAGE instrument was used in its ground configuration to make measurements of OH and HO2
at the Cape Verde Observatory.
Seasonal influences on OH and HO2 chemistry were investigated during three intensive measurement campaigns
made in three distinct seasonal periods; SOS1 during February-March (generally dry with clear sky), in June during SOS2 (clear and dry),
and SOS3 in September (some sustained periods of heavy rainfall). Preliminary data analysis suggests mean midday concentrations of OH were
3.6, 3.5 and 4.6 × 106 cm-3 for SOS1, 2 and 3; the corresponding mean noontime concentrations of HO2
were 1.8, 2.1 and 1.8 × 108 cm-3. Compared to measurements made in May-June 2007, during the RHAMBLE
project the peak concentration of HO2 for SOS2 seem similar, whereas the concentration of OH in SOS2 appears about 30 % lower.
OP3 - Borneo (2008)
The Oxidant and Particle Photochemical Processes project over a South-East Asian tropical rain forest took place in
Borneo in 2008, conisting of two intensive ground based campaigns and an aircraft campaign to coincide with the
second ground-based measurement period.
The FAGE group took part in all three measurement campaigns. Despite low ozone concentrations, limiting primary
production of OH from ozone photolysis, ground based observations found significant OH levels - up to 8.7 x 106
molecule cm-3. In addition, the OH lifetime instrument measured high OH reactivity, corresponding to a lifetime
for OH approaching 10 ms, indicating that significant additional OH sources must be present.
OH concentrations up to 6 x 105 molecule cm-3 were also recorded
on several nights after j(O1D) had dropped to zero, suggesting a non-photolytic source of OH.
COBRA - Canada (2008)
Direct measurements of OH and HO2 radical concentrations were made, using the University of Leeds FAGE instrument,
as part of the COBRA (Combined Impact of Iodine and Bromine Release on the Arctic Atmosphere) campaign, on the coast of Hudson Bay during spring 2008.
Mean noontime OH and HO2 concentrations of (0.765 ± 1.05) x 106 molecule cm-3
and (1.34 ± 0.62) x 108 molecule cm-3 respectively, were observed. These observations were used in conjunction
with a box model, constrained to supporting observations, to asses the radical budget in this cold, northerly environment.
HCHO photolysis was found to be the dominant daytime radical source, providing 74 % of the observed HOx,
with observed HCHO concentrations requiring the presence of a considerable (>80%) surface source. Model simulations also suggest
significant roles for halogen chemistry and the heterogeneous loss of HO2. The formation of HO2NO2
has been identified as playing an important role as a radical reservoir, reducing HOx concentrations during the day, and thus
impacting both local oxidising capacity and ozone production. The sensitivity of the local chemistry to uncertainties in these
processes is explored, the majority of which are not represented in global chemistry models.
RHaMBLe - Cape Verde Campaign (2007)
The Reactive Halogen Marine Boundary Layer project aimed to quantify the impact of reactive halogen species
at both coastal and open ocean locations. The second leg of the project, focussing on open ocean impacts, took place at
the Cape Verde Observatory in 2007.
Located ~ 500 km off the West coast of Africa, the site predominantly samples background, tropical
marine boundary layer air.
During the project the ground-based FAGE instrument made measurements of OH and HO2. Owing to high humidity
and low solar zenith angle experienced at the site midday OH concentrations reached around 1 x 107 molecule
cm-3 and HO2 levels were as high as 7 x 108 molecule cm-3 on some days.
Although the halogen oxide concentration in this region is low, steady state analysis of the HOx radicals highlights
that reaction of HO2 with IO and BrO radicals acts as a major HO2 sink in this region, whilst photolysis
of the reaction products (HOI and HOBr) is an important OH source.
This work demonstrates the importance of halogen chemistry in the remote MBL and that to accurately predict global OH levels
this chemistry should be included in model simulations.
Whalley, L.K.; Furneaux, K.L.; Goddard, A.; Lee, J.D.; Mahajan, A.; Oetjen, H.; Read, K.A.; Kaaden, N.;
Carpenter, L.J.; Lewis, A.C.; Plane, J.M.C.; Saltzman, E.S.; Wiedensohler, A.; Heard, D.E.
The chemistry of OH and HO2 radicals in the boundary layer over the tropical Atlantic Ocean,
Atmospheric Chemistry and Physics, 2010, 10, 1555-1576
Read, K.A.; Mahajan, A.S.; Carpenter, L.J.; Evans, M.J.; Faria, B.V.E.; Heard, D.E.; Hopkins, J.R.; Lee, J.D.; Moller, S.J.; Lewis, A.C.; Mendes, L.; McQuaid, J.B.;
Oetjen, H.; Saiz-Lopez, A.; Pilling, M.J.; Plane, J.M.C.
Extensive halogen-mediated ozone destruction over the tropical Atlantic Ocean,
Nature, 2008, 453, 7159, 2332-1235
CHABLIS Campaign (2005)
The CHABLIS project took place at the Halley Research Station, Antarctica from Jan 2004 - Feb 2005. The ground-based FAGE instrument
was deployed at the site during the austral summer of 2005 and made round-the-clock measurements of OH and HO2
for 6 weeks. Peak OH and HO2 concentrations were ~ 8 x 105 molecule cm-3 and 3.8
x 107 molecule cm -3 respectively.
Photolysis of O3 and formaldehyde were found to be the dominant source of the radicals, whilst,
NOx, originating from snowpack photochemistry, and the halogen oxides present, were the dominant
species leading to radical inter-conversion and enhancement of OH.
Bloss, W.J.; Lee, J.D.; Heard, D.E.; Salmon, R.A.; Bauguitte, S.J.-B.; Roscoe, H.K.; Jones, A.E. , Observations of OH and HO2
radicals in coastal Antarctica, Atmospheric Chemistry and Physics,, pp.4171-4185, 2007, 7
NAMBLEX Campaign (2002)
The North Atlantic Marine Boundary Layer Experiment took place at Mace Head, Ireland in the summer
One of the main aims of the NAMBLEX campaign involved the comparison of concentration measurements of a range of
free radical species (OH, HO2, RO2 and NO3) with calculations of a zero-dimensional box model based on the MCM, allowing a
quantitative test of the basic understanding of oxidation processes in clean and moderately polluted MBL air.
Through this work the importance of halogen chemistry and aerosols upon HOx levels was demonstrated.
Bloss, W.; Lee J.D.; Johnson G.P.;
Sommariva R.; Heard, D.E.; Saiz-Lopez, A.; Plane, J.M.C.; McFiggans, G.; Coe H.;
Flynn, M.; Williams, P.; Rickard A.R.; Fleming, Z.L. , Impact of halogen
monoxide chemistry upon boundary layer OH and HO2 concentrations at a
coastal site , Geophysical Research Letters, , pp.L06814 , 2005 ,
American Geophysical Union , 32
Smith S.C.; Lee J.D.L.; Bloss, W.;
Johnson G.P.; Heard, D.E. , Concentrations of OH and HO2 radicals
during NAMBLEX: Measurements and steady-state calculations, Atmospheric
Chemistry and Physics Discussions, , pp.12403-12464 , 2005 , European
Geophysical Society , 5
Fleming Z.L.; Monks P.S.; Rickard A.R.; Heard,
D.E.; Bloss, W.; Seakins, P.W.; Sommariva R.; Pilling, M.J.; Morgan R.; Green,
T.J.; Brough N.; Mills, G.P.; Penkett S.A.; Lee J.D.L.; Saiz-Lopez A.; Plane
J.M.C. , Peroxy radical chemistry and the control of ozone photochemistry at
Mace Head, Ireland, Summer of 2002, Atmospheric Chemistry and Physics
Discussions, , pp.12313-12371 , 2005 , European Geophysical Society , 5
Heard, D.E.; Read, KA.; Methven, J.; Al Haider, S.; Bloss, W.; de Leeuw,
G.; Johnson, G.P.; Pilling, M.J.; Seakins, P.W.; Smith, S.C.; Sommariva, R.;
Stanton, J.; Still, T.; Brooks, B.J.; Jackson, A.V.; McQuaid, J.B.; Morgan, R.;
Smith, M.H.; Carpenter, L.J.; Carslaw, N.; Hamilton, J.F.; Hopkins, J.R.; Lee,
J.D.; Lewis, A.C.; Purvis, R.M.; Wevill, D.J.; Brough, N.; Green, T.J.; Mills,
G.P.; Penkett, S.A.; Plane, J.M.C.; Saiz-Lopez, A.; Worton, D.; Monks, P.S.;
Fleming, Z.L.; Rickard, A.R.; Alfarra, M.; Allan, J.D.; Bower, K.; Coe, H.;
Cubison, M.; Flynn, M.; McFiggans, G.; Gallagher, M.W.; Norton, E.G.; O'Dowd,
C.D.; Shillito, J.; Topping, D.; Vaughan, G.; Williams, P.; Bitter, M.; Ball,
S.M.; Jones, R.L.; Povey, I.M.; O'Doherty, S.; Simmonds, P.G.; Allen, A.;
Kinnersley, R.P.; Beddows, D.C.S.; Dall'Osto, M.; Harrison, R.M.; Donovan, R.J.;
Heal, M.R.; Jennings, S.G.; Noone, C.; Spain, G. , The North Atlantic Marine
Boundary Layer Experiment (NAMBLEX). Overview of the Mace Head, Ireland, in
Summer 2002, Atmospheric Chemistry and Physics Discussions, ,
pp.12177-12254 , 2005 , European Geophysical Society , 5
Bloss, W.; Brough N.; Carslaw N.; Flynn M.; Haggerstone A.L.; Heard D.E.;
Hopkins J.R.; Lee J.D.L.; Lewis A.C.; McFiggans G.; Monks P.S.; Penkett S.A.;
Pilling, M.J.; Plane J.M.C.; Read K.; Saiz-Lopez A.; Rickard A.R.; Williams P. ,
OH and HO2 chemistry during NAMBLEX: roles of oxygenates, halogen
oxides and heterogeneous uptake, Atmospheric Chemistry and Physics
Discussions, , pp.10947-10996 , 2005 , European Geophysical Society , 5
PUMA Campaign (1999/2000)
The Pollution in the Urban West
Midlands project was sponsered by NERC under the Urban
Regeneration in the Environment thermatic program. The aim of the project was
to comprehensively monitor urban air quality over two four week field
campaigns in the summer of 1999 and winter of 2000 at a central site within
the West Midlands. Measurements of OH and HO2 in urban areas are
scarce, and this campaign provided the first example of such measurements in
Emmerson K.M.; Carslaw N.; Carpenter
L.J.; Heard, D.E.; Lee J.D.L.; Pilling, M.J. , Urban Atmospheric Chemistry
During the PUMA Campaign 1: Comparison of modelled OH and HO2 concentrations
with measurements, Journal of Atmospheric Chemistry, , pp.142-164 ,
2005 , Kluwer Academic Publishers , 52
Heard D.E.; Carpenter L.J.; Creasey D.J.; Hopkins J.R.; Lee J.D.L.;
Lewis A.C.; Pilling M.J.; Seakins P.W.; Carslaw N.; Emmerson, K.M. , High
levels of the hydroxyl radical in the winter urban troposphere,
Geophysical Research Letters, , pp.L18112 , 2004 , American Geophysical
Union , 31