Peroxy radical chemistry and the control of ozone photochemistry at Mace Head, Ireland during the summer of 2002

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 model/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 [NO2] 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.

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Peroxy radical chemistry and the control of ozone photochemistry at Mace Head, Ireland during the summer of 2002

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-5-12313-2005 ◽

2005 ◽

Vol 5 (6) ◽

pp. 12313-12371 ◽

Cited By ~ 4

Author(s):

Z. L. Fleming ◽

P. S. Monks ◽

A. R. Rickard ◽

D. E. Heard ◽

W. J. Bloss ◽

...

Keyword(s):

Boundary Layer ◽

Production Rate ◽

Marine Boundary Layer ◽

Strong Dependence ◽

Peroxy Radical ◽

Chemical Mechanism ◽

Ozone Production ◽

Peroxy Radicals ◽

Night Time ◽

Model Measurement

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 model/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.

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Radicals in the marine boundary layer during NEAQS 2004: a model study of day-time and night-time sources and sinks

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-3075-2009 ◽

2009 ◽

Vol 9 (9) ◽

pp. 3075-3093 ◽

Cited By ~ 24

Author(s):

R. Sommariva ◽

H. D. Osthoff ◽

S. S. Brown ◽

T. S. Bates ◽

T. Baynard ◽

...

Keyword(s):

Boundary Layer ◽

New England ◽

Gas Phase ◽

Marine Boundary Layer ◽

Peroxy Radical ◽

Chemical Mechanism ◽

Physical Parameters ◽

Peroxy Radicals ◽

Night Time ◽

Aerosol Composition

Abstract. This paper describes a modelling study of several HOx and NOx species (OH, HO2, organic peroxy radicals, NO3 and N2O5) in the marine boundary layer. A model based upon the Master Chemical Mechanism (MCM) was constrained to observations of chemical and physical parameters made onboard the NOAA ship R/V Brown as part of the New England Air Quality Study (NEAQS) in the summer of 2004. The model was used to calculate [OH] and to determine the composition of the peroxy radical pool. Modelled [NO3] and [N2O5] were compared to in-situ measurements by Cavity Ring-Down Spectroscopy. The comparison showed that the model generally overestimated the measurements by 30–50%, on average. The model results were analyzed with respect to several chemical and physical parameters, including uptake of NO3 and N2O5 on fog droplets and on aerosol, dry deposition of NO3 and N2O5, gas-phase hydrolysis of N2O5 and reactions of NO3 with NMHCs and peroxy radicals. The results suggest that fog, when present, is an important sink for N2O5 via rapid heterogeneous uptake. The comparison between the model and the measurements were consistent with values of the heterogeneous uptake coefficient of N2O5 (γN2O5)>1×10−2, independent of aerosol composition in this marine environment. The analysis of the different loss processes of the nitrate radical showed the important role of the organic peroxy radicals, which accounted for a significant fraction (median: 15%) of NO3 gas-phase removal, particularly in the presence of high concentrations of dimethyl sulphide (DMS).

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Radicals in the marine boundary layer during NEAQS 2004: a model study of day-time and night-time sources and sinks

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-16643-2008 ◽

2008 ◽

Vol 8 (4) ◽

pp. 16643-16692 ◽

Cited By ~ 5

Author(s):

R. Sommariva ◽

H. D. Osthoff ◽

S. S. Brown ◽

T. S. Bates ◽

T. Baynard ◽

...

Keyword(s):

Boundary Layer ◽

New England ◽

Gas Phase ◽

Marine Boundary Layer ◽

Peroxy Radical ◽

Chemical Mechanism ◽

Physical Parameters ◽

Peroxy Radicals ◽

Night Time ◽

Aerosol Composition

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Night-time radical chemistry during the NAMBLEX campaign

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-587-2007 ◽

2007 ◽

Vol 7 (3) ◽

pp. 587-598 ◽

Cited By ~ 21

Author(s):

R. Sommariva ◽

M. J. Pilling ◽

W. J. Bloss ◽

D. E. Heard ◽

J. D. Lee ◽

...

Keyword(s):

Boundary Layer ◽

Marine Boundary Layer ◽

Chemical Mechanism ◽

Optical Absorption Spectroscopy ◽

Peroxy Radicals ◽

Night Time ◽

Measured Concentration ◽

Light Alkenes ◽

The North ◽

Order Of Magnitude

Abstract. Night-time chemistry in the Marine Boundary Layer has been modelled using a number of observationally constrained zero-dimensional box-models. The models were based upon the Master Chemical Mechanism (MCM) and the measurements were taken during the North Atlantic Marine Boundary Layer Experiment (NAMBLEX) campaign at Mace Head, Ireland in July–September 2002. The model could reproduce, within the combined uncertainties, the measured concentration of HO2 (within 30–40%) during the night 31 August–1 September and of HO2+RO2 (within 15–30%) during several nights of the campaign. The model always overestimated the NO3 measurements made by Differential Optical Absorption Spectroscopy (DOAS) by up to an order of magnitude or more, but agreed with the NO3 Cavity Ring-Down Spectroscopy (CRDS) measurements to within 30–50%. The most likely explanation of the discrepancy between the two instruments and the model is the reaction of the nitrate radical with inhomogeneously distributed NO, which was measured at concentrations of up to 10 ppt, even though this is not enough to fully explain the difference between the DOAS measurements and the model. A rate of production and destruction analysis showed that radicals were generated during the night mainly by the reaction of ozone with light alkenes. The cycling between HO2/RO2 and OH was maintained during the night by the low concentrations of NO and the overall radical concentration was limited by slow loss of peroxy radicals to form peroxides. A strong peak in [NO2] during the night 31 August–1 September allowed an insight into the radical fluxes and the connections between the HOx and the NO3 cycles.

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Night-time radical chemistry during the NAMBLEX campaign

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-6-7715-2006 ◽

2006 ◽

Vol 6 (4) ◽

pp. 7715-7745 ◽

Cited By ~ 2

Author(s):

R. Sommariva ◽

M. J. Pilling ◽

W. J. Bloss ◽

D. E. Heard ◽

J. D. Lee ◽

...

Keyword(s):

Boundary Layer ◽

Marine Boundary Layer ◽

Chemical Mechanism ◽

Optical Absorption Spectroscopy ◽

Peroxy Radicals ◽

Night Time ◽

Measured Concentration ◽

Light Alkenes ◽

The North ◽

Order Of Magnitude

Abstract. Night-time chemistry in the Marine Boundary Layer has been modelled using a number of observationally constrained zero-dimensional box-models. The models were based upon the Master Chemical Mechanism (MCM) and the measurements were taken during the North Atlantic Marine Boundary Layer Experiment (NAMBLEX) campaign at Mace Head, Ireland in July–September 2002. The model could reproduce, within the combined uncertainties, the measured concentration of HO2 (within 30–40%) during the night 31 August–1 September and of HO2+RO2 (within 15–30%) during several nights of the campaign. The model always overestimated the NO3 measurements made by Differential Optical Absorption Spectroscopy (DOAS) by up to an order of magnitude or more, but agreed with the NO3 Cavity Ring-Down Spectroscopy (CRDS) measurements to within 30–50%. The most likely explanation of the discrepancy between the two instruments and the model is reaction of the nitrate radical with inhomogeneously distributed NO, which was measured at concentrations of up to 10 ppt, even though this is not enough to fully explain the difference between the DOAS measurements and the model. A rate of production and destruction analysis showed that radicals were generated during the night mainly by the reaction of ozone with light alkenes. The cycling between HO2/RO2 and OH was maintained during the night by the low concentrations of NO and the overall radical concentration was limited by slow loss of peroxy radicals to form peroxides. A strong peak in [NO2] during the night 31 August–1 September allowed an insight into the radical fluxes and the connections between the HOx and the NO3 cycles.

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Understanding in situ ozone production in the summertime through radical observations and modelling studies during the Clean air for London project (ClearfLo)

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-2547-2018 ◽

2018 ◽

Vol 18 (4) ◽

pp. 2547-2571 ◽

Cited By ~ 20

Author(s):

Lisa K. Whalley ◽

Daniel Stone ◽

Rachel Dunmore ◽

Jacqueline Hamilton ◽

James R. Hopkins ◽

...

Keyword(s):

Elevated Temperatures ◽

Degradation Mechanism ◽

Peroxy Radical ◽

Box Model ◽

Chemical Mechanism ◽

Ozone Production ◽

Peroxy Radicals ◽

Sink Term ◽

Modelling Studies ◽

Model Measurement

Abstract. Measurements of OH, HO2, RO2i (alkene and aromatic-related RO2) and total RO2 radicals taken during the ClearfLo campaign in central London in the summer of 2012 are presented. A photostationary steady-state calculation of OH which considered measured OH reactivity as the OH sink term and the measured OH sources (of which HO2+ NO reaction and HONO photolysis dominated) compared well with the observed levels of OH. Comparison with calculations from a detailed box model utilising the Master Chemical Mechanism v3.2, however, highlighted a substantial discrepancy between radical observations under lower NOx conditions ([NO] < 1 ppbv), typically experienced during the afternoon hours, and indicated that the model was missing a significant peroxy radical sink; the model overpredicted HO2 by up to a factor of 10 at these times. Known radical termination steps, such as HO2 uptake on aerosols, were not sufficient to reconcile the model–measurement discrepancies alone, suggesting other missing termination processes. This missing sink was most evident when the air reaching the site had previously passed over central London to the east and when elevated temperatures were experienced and, hence, contained higher concentrations of VOCs. Uncertainties in the degradation mechanism at low NOx of complex biogenic and diesel related VOC species, which were particularly elevated and dominated OH reactivity under these easterly flows, may account for some of the model–measurement disagreement. Under higher [NO] (> 3 ppbv) the box model increasingly underpredicted total [RO2]. The modelled and observed HO2 were in agreement, however, under elevated NO concentrations ranging from 7 to 15 ppbv. The model uncertainty under low NO conditions leads to more ozone production predicted using modelled peroxy radical concentrations (∼ 3 ppbv h−1) versus ozone production from peroxy radicals measured (∼ 1 ppbv h−1). Conversely, ozone production derived from the predicted peroxy radicals is up to an order of magnitude lower than from the observed peroxy radicals as [NO] increases beyond 7 ppbv due to the model underprediction of RO2 under these conditions.

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Free radical modelling studies during the UK TORCH Campaign in Summer 2003

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-167-2007 ◽

2007 ◽

Vol 7 (1) ◽

pp. 167-181 ◽

Cited By ~ 115

Author(s):

K. M. Emmerson ◽

N. Carslaw ◽

D. C. Carslaw ◽

J. D. Lee ◽

G. McFiggans ◽

...

Keyword(s):

Hydroxyl Radical ◽

Atmospheric Chemistry ◽

Model Performance ◽

Peroxy Radical ◽

Chemical Mechanism ◽

Ozone Production ◽

Peroxy Radicals ◽

North East ◽

Hydroperoxy Radical ◽

Modelling Studies

Abstract. The Tropospheric ORganic CHemistry experiment (TORCH) took place during the heatwave of summer 2003 at Writtle College, a site 2 miles west of Chelmsford in Essex and 25 miles north east of London. The experiment was one of the most highly instrumented to date. A combination of a large number of days of simultaneous, collocated measurements, a consequent wealth of model constraints and a highly detailed chemical mechanism, allowed the atmospheric chemistry of this site to be studied in detail. Between 25 July and 31 August, the concentrations of the hydroxyl radical and the hydroperoxy radical were measured using laser-induced fluorescence at low pressure and the sum of peroxy radicals was measured using the peroxy radical chemical amplifier technique. The concentrations of the radical species were predicted using a zero-dimensional box model based on the Master Chemical Mechanism version 3.1, which was constrained with the observed concentrations of relatively long-lived species. The model included a detailed parameterisation to account for heterogeneous loss of hydroperoxy radicals onto aerosol particles. Quantile-quantile plots were used to assess the model performance in respect of the measured radical concentrations. On average, measured hydroxyl radical concentrations were over-predicted by 24%. Modelled and measured hydroperoxy radical concentrations agreed very well, with the model over-predicting on average by only 7%. The sum of peroxy radicals was under-predicted when compared with the respective measurements by 22%. Initiation via OH was dominated by the reactions of excited oxygen atoms with water, nitrous acid photolysis and the ozone reaction with alkene species. Photolysis of aldehyde species was the main route for initiation via HO2 and RO2. Termination, under all conditions, primarily involved reactions with NOx for OH and heterogeneous chemistry on aerosol surfaces for HO2. The OH chain length varied between 2 and 8 cycles, the longer chain lengths occurring before and after the most polluted part of the campaign. Peak local ozone production of 17 ppb hr−1 occurred on 3 and 5 August, signifying the importance of local chemical processes to ozone production on these days. On the whole, agreement between model and measured radicals is good, giving confidence that our understanding of atmospheres influenced by nearby urban sources is adequate.

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Missing peroxy radical sources within a summertime ponderosa pine forest

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-4715-2014 ◽

2014 ◽

Vol 14 (9) ◽

pp. 4715-4732 ◽

Cited By ~ 31

Author(s):

G. M. Wolfe ◽

C. Cantrell ◽

S. Kim ◽

R. L. Mauldin III ◽

T. Karl ◽

...

Keyword(s):

Ponderosa Pine ◽

Forest Canopy ◽

Strong Dependence ◽

Rocky Mountain ◽

Peroxy Radical ◽

Pine Forest ◽

Chemical Mechanism ◽

Peroxy Radicals ◽

Mixing Ratios ◽

Ponderosa Pine Forest

Abstract. Organic peroxy (RO2) and hydroperoxy (HO2) radicals are key intermediates in the photochemical processes that generate ozone, secondary organic aerosol and reactive nitrogen reservoirs throughout the troposphere. In regions with ample biogenic hydrocarbons, the richness and complexity of peroxy radical chemistry presents a significant challenge to current-generation models, especially given the scarcity of measurements in such environments. We present peroxy radical observations acquired within a ponderosa pine forest during the summer 2010 Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen – Rocky Mountain Organic Carbon Study (BEACHON-ROCS). Total peroxy radical mixing ratios reach as high as 180 pptv (parts per trillion by volume) and are among the highest yet recorded. Using the comprehensive measurement suite to constrain a near-explicit 0-D box model, we investigate the sources, sinks and distribution of peroxy radicals below the forest canopy. The base chemical mechanism underestimates total peroxy radicals by as much as a factor of 3. Since primary reaction partners for peroxy radicals are either measured (NO) or underpredicted (HO2 and RO2, i.e., self-reaction), missing sources are the most likely explanation for this result. A close comparison of model output with observations reveals at least two distinct source signatures. The first missing source, characterized by a sharp midday maximum and a strong dependence on solar radiation, is consistent with photolytic production of HO2. The diel profile of the second missing source peaks in the afternoon and suggests a process that generates RO2 independently of sun-driven photochemistry, such as ozonolysis of reactive hydrocarbons. The maximum magnitudes of these missing sources (~120 and 50 pptv min−1, respectively) are consistent with previous observations alluding to unexpectedly intense oxidation within forests. We conclude that a similar mechanism may underlie many such observations.

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Seasonal dependence of peroxy radical concentrations at a northern hemisphere marine boundary layer site during summer and winter: evidence for photochemical activity in winter

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-6-7235-2006 ◽

2006 ◽

Vol 6 (4) ◽

pp. 7235-7284

Author(s):

Z. L. Fleming ◽

P. S. Monks ◽

A. R. Rickard ◽

B. J. Bandy ◽

N. Brough ◽

...

Keyword(s):

Marine Boundary Layer ◽

Peroxy Radical ◽

Photochemical Activity ◽

Ozone Production ◽

Peroxy Radicals ◽

Large Variability ◽

Diurnal Cycles ◽

Photostationary State ◽

Radical Concentration

Abstract. Peroxy radicals (HO2+ΣRO2) were measured at the Weybourne Atmospheric Observatory (52° N, 1° E), Norfolk using a PEroxy Radical Chemical Amplifier (PERCA) during the winter and summer of 2002. The peroxy radical diurnal cycles showed a marked difference between the winter and summer campaigns with maximum concentrations of 12 pptv at midday in the summer and maximum concentrations as high as 30 pptv (10 min averages) in winter at night. The corresponding nighttime peroxy radical concentrations were not as high in summer (3 pptv). The peroxy radical concentration shows a distinct anti-correlation with increasing NOx during the daylight hours. At night, peroxy radicals increase with increasing NOx indicative of the role of NO3 chemistry. The average diurnal cycles for net ozone production, N(O3) show a large variability in ozone production, P(O3), and a large ozone loss, L(O3) in summer relative to winter. For a daylight average, net ozone production in summer than winter (1.51±0.5 ppbv h−1 and 1.11±0.47 ppbv h−1 respectively) but summer shows more variability of (meteorological) conditions than winter. The variability in NO concentration has a much larger effect on N(O3) than the peroxy radical concentrations. Photostationary state (PSS) calculations show an NO2 lifetime of 5 min in summer and 21 min in the winter, implying that steady-state NO-NO2 ratios are not always attained during the winter months. The results show an active peroxy radical chemistry at night and the ability of winter to make oxidant. The net effect of this with respect to production of ozone in winter is unclear owing to the breakdown in the photostationary state.

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