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Title: Peroxy radical chemistry and the control of ozone photochemistry at Mace Head, Ireland, during the summer of 2002
Authors: Fleming, Zoe L.
Monks, Paul S.
Rickard, Andrew R.
Heard, Dwayne E.
Bloss, William J.
Seakins, Paul W.
Still, T.J.
Sommariva, R.
Pilling, Michael J.
Morgan, R.
Green, T.J.
Brough, N.
Mills, Graham P.
Penkett, Stuart A.
Lewis, Alastair C.
Lee, James D.
Saiz-Lopez, A.
Plane, J.M.C.
First Published: 2006
Publisher: European Geosciences Union
Citation: Atmospheric Chemistry and Physics, 2006, 6, pp.2193-2214
Abstract: Peroxy radical (HO2 +ΣRO2) measurements, using the PEroxy Radical Chemical Amplification (PERCA) technique at the North Atlantic Marine Boundary Layer EXperiment (NAMBLEX) at Mace Head in summer 2002, are presented and put into the context of marine, boundary-layer chemistry. A suite of other chemical parameters (NO, NO2, NO3, CO, CH4, O3, VOCs, peroxides), photolysis frequencies and meteorological measurements, are used to present a detailed analysis of the role of peroxy radicals in tropospheric oxidation cycles and ozone formation. Under the range of conditions encountered the peroxy radical daily maxima varied from 10 to 40 pptv. The diurnal cycles showed an asymmetric shape typically shifted to the afternoon. Using a box model based on the master chemical mechanism the average model measurement agreement was 2.5 across the campaign. The addition of halogen oxides to the model increases the level of odel/measurement agreement, apparently by respeciation of HOx. A good correlation exists between j(HCHO).[HCHO] and the peroxy radicals indicative of the importance of HCHO in the remote atmosphere as a HOx source, particularly in the afternoon. The peroxy radicals showed a strong dependence on [NOx] with a break point at 0.1 ppbv, where the radicals increased concomitantly with the reactive VOC loading, this is a lower value than seen at representative urban campaigns. The HO2/(HO2 + ΣRO2) ratios are dependent on [NOx] ranging between 0.2 and 0.6, with the ratio increasing linearly with NOx. Significant night-time levels of peroxy radicals were measured up to 25 pptv. The contribution of ozone-alkenes and NO3-alkene chemistry to night-time peroxy radical production was shown to be on average 59 and 41%. The campaign mean net ozone production rate was 0.11±0.3 ppbv h−1. The ozone production rate was strongly dependent on [NO] having linear sensitivity (dln(P(O3))/dln(NO)=1.0). The results imply that the N(O3) (the in-situ net photochemical rate of ozone production/destruction) will be strongly sensitive in the marine boundary layer to small changes in [NO] which has ramifications for changing NOx loadings in the European continental boundary layer.
Type: Article
Description: This work is licensed under a Creative Commons License and is also available from, along with further discussion.
Appears in Collections:Published Articles, Dept. of Chemistry

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