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

2008 ◽  
Vol 8 (4) ◽  
pp. 16643-16692 ◽  
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).

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

2009 ◽  
Vol 9 (9) ◽  
pp. 3075-3093 ◽  
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).

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

2006 ◽  
Vol 6 (8) ◽  
pp. 2193-2214 ◽  
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 [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.

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

2005 ◽  
Vol 5 (6) ◽  
pp. 12313-12371 ◽  
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.

scholarly journals Night-time radical chemistry during the NAMBLEX campaign

2007 ◽  
Vol 7 (3) ◽  
pp. 587-598 ◽  
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.

scholarly journals Night-time radical chemistry during the NAMBLEX campaign

2006 ◽  
Vol 6 (4) ◽  
pp. 7715-7745 ◽  
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.

scholarly journals The chemistry of OH and HO<sub>2</sub> radicals in the boundary layer over the tropical Atlantic Ocean

2009 ◽  
Vol 9 (4) ◽  
pp. 15959-16009 ◽  
Author(s):  
L. K. Whalley ◽  
K. L. Furneaux ◽  
A. Goddard ◽  
J. D. Lee ◽  
A. Mahajan ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Chemical Mechanism ◽  
Physical Parameters ◽  
Tropical Atlantic ◽  
Instantaneous Rate ◽  
Ozone Destruction ◽  
Halogen Chemistry ◽  
Gas Expansion ◽  
Halogen Oxides

Abstract. Fluorescence Assay by Gas Expansion (FAGE) has been used to detect ambient levels of OH and HO2 radicals at the Cape Verde Atmospheric Observatory, located in the tropical Atlantic marine boundary layer, during May and June 2007. Midday radical concentrations were high, with maximum concentrations of 9×106 molecule cm−3 and 6×108 molecule cm−3 observed for OH and HO2, respectively. A box model incorporating the detailed Master Chemical Mechanism, extended to include halogen chemistry, and constrained by all available measurements including halogen and nitrogen oxides, has been used to assess the chemical and physical parameters controlling the radical chemistry. IO and BrO, although present only at a few pptv, constituted ~23% of the instantaneous sinks for HO2. Modelled HO2 was sensitive to both HCHO concentration and the rate of heterogeneous loss to the ocean surface and aerosols. However, a unique combination of these parameters could not be found that gave optimised (to within 15%) agreement during both the day and night. The results imply a missing nighttime source of HO2. The model underpredicted the daytime (sunrise to sunset) OH concentration by 12%. Photolysis of HOI and HOBr accounted for ~13% of the instantaneous rate of OH formation. Taking into account that halogen oxides increase the oxidation of NOx (NO→NO2), and in turn reduce the rate of formation of OH from the reaction of HO2 with NO, OH concentrations were estimated to be 10% higher overall due to the presence of halogens. The increase in modelled OH from halogen chemistry gives an estimated 10% shorter lifetime for methane in this region, and the inclusion of halogen chemistry is necessary to model the observed daily cycle of ozone destruction that is observed at the surface. Due to surface losses, we hypothesise that HO2 concentrations increase with height and therefore contribute a larger fraction of the ozone destruction than at the surface.

scholarly journals The influence of cloud chemistry on HO<sub>x</sub> and NO<sub>x</sub> in the Marine Boundary Layer: a 1-D modelling study

2001 ◽  
Vol 1 (2) ◽  
pp. 277-335
Author(s):  
J. E. Williams ◽  
F. J. Dentener ◽  
A. R. van den Berg
Keyword(s):  
Boundary Layer ◽  
Gas Phase ◽  
Marine Boundary Layer ◽  
Phase Transfer ◽  
Cloud Model ◽  
Chemical Mechanism ◽  
Marine Stratocumulus ◽  
Modelling Studies ◽  
A Minor ◽  
The Impact

Abstract. A 1-D marine stratocumulus cloud model has been supplemented with a comprehensive and up-to-date aqueous phase chemical mechanism for the purpose of assessing the impact that the presence of clouds and aerosols has on gas phase HOx, NOx and O3 budgets in the marine boundary layer. The simulations presented here indicate that cloud may act as a heterogeneous source of HONOg via the conversion of HNO4(g) at moderate pH (~4.5). The photolysis of nitrate (NO3-) has also been found to contribute to this simulated increase in HONOg by ~5% and also acts as a minor source of NO2(g). The effect of introducing deliquescent aerosol on the simulated increase of HONOg is negligible. The most important consequences of this elevation in HONOg are that, in the presence of cloud, gas phase concentrations of NOx species increase by a factor of 2, which minimises the simulated decrease in O3(g), and results in a regeneration of OHg. This partly compensates for the removal of OHg by direct phase transfer into the cloud and has important implications regarding the oxidising capacity of the marine boundary layer. The findings presented here also suggest that previous modelling studies, which neglect the heterogeneous HNO4(g) reaction cycle, may have over-estimated the role of clouds as a sink for OHg and O3(g)in unpolluted oceanic regions, by ~10% and ~2%, respectively.

scholarly journals The chemistry of OH and HO<sub>2</sub> radicals in the boundary layer over the tropical Atlantic Ocean

2010 ◽  
Vol 10 (4) ◽  
pp. 1555-1576 ◽  
Author(s):  
L. K. Whalley ◽  
K. L. Furneaux ◽  
A. Goddard ◽  
J. D. Lee ◽  
A. Mahajan ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Chemical Mechanism ◽  
Sensitivity Analyses ◽  
Physical Parameters ◽  
Tropical Atlantic ◽  
Halogen Chemistry ◽  
Gas Expansion ◽  
Halogen Oxides

Abstract. Fluorescence Assay by Gas Expansion (FAGE) has been used to detect ambient levels of OH and HO2 radicals at the Cape Verde Atmospheric Observatory, located in the tropical Atlantic marine boundary layer, during May and June 2007. Midday radical concentrations were high, with maximum concentrations of 9 ×106 molecule cm−3 and 6×108 molecule cm−3 observed for OH and HO2, respectively. A box model incorporating the detailed Master Chemical Mechanism, extended to include halogen chemistry, heterogeneous loss processes and constrained by all available measurements including halogen and nitrogen oxides, has been used to assess the chemical and physical parameters controlling the radical chemistry. The model was able to reproduce the daytime radical concentrations to within the 1 σ measurement uncertainty of 20% during the latter half of the measurement period but significantly under-predicted [HO2] by 39% during the first half of the project. Sensitivity analyses demonstrate that elevated [HCHO] (~2 ppbv) on specific days during the early part of the project, which were much greater than the mean [HCHO] (328 pptv) used to constrain the model, could account for a large portion of the discrepancy between modelled and measured [HO2] at this time. IO and BrO, although present only at a few pptv, constituted ~19% of the instantaneous sinks for HO2, whilst aerosol uptake and surface deposition to the ocean accounted for a further 23% of the HO2 loss at noon. Photolysis of HOI and HOBr accounted for ~13% of the instantaneous OH formation. Taking into account that halogen oxides increase the oxidation of NOx (NO → NO2), and in turn reduce the rate of formation of OH from the reaction of HO2 with NO, OH concentrations were estimated to be 9% higher overall due to the presence of halogens. The increase in modelled OH from halogen chemistry gives an estimated 9% shorter lifetime for methane in this region, and the inclusion of halogen chemistry is necessary to model the observed daily cycle of O3 destruction that is observed at the surface. Due to surface losses, we hypothesise that HO2 concentrations increase with height and therefore contribute a larger fraction of the O3 destruction than at the surface.

scholarly journals The influence of cloud chemistry on HO<sub>x</sub> and NO<sub>x</sub> in the moderately polluted marine boundary layer: a 1-D modelling study

2002 ◽  
Vol 2 (1) ◽  
pp. 39-54 ◽  
Author(s):  
J. E. Williams ◽  
F. J. Dentener ◽  
A. R. van den Berg
Keyword(s):  
Boundary Layer ◽  
Gas Phase ◽  
Marine Boundary Layer ◽  
Phase Transfer ◽  
Cloud Model ◽  
Chemical Mechanism ◽  
Cloud Chemistry ◽  
Marine Stratocumulus ◽  
The Impact ◽  
Heterogeneous Source

Abstract. A 1-D marine stratocumulus cloud model has been supplemented with a comprehensive and up-to-date aqueous phase chemical mechanism for the purpose of assessing the impact that the presence of clouds has on gas phaseHOx, NOx and O3 budgets in the marine boundary layer. The simulations presented here indicate that cloud may act as a heterogeneous source of HONOg. The conversion of HNO4(g) at moderate pH (~ 4.5) is responsible for this, and, to a lesser extent, the photolysis of nitrate (NO3-). The effect of introducing deliquescent aerosol on the simulated increase of HONOg is negligible. The most important consequences of this elevation in HONOg are that, in the presence of cloud, gas phase concentrations of NOx species increase by a factor of 2, which minimises the simulated decrease in O3(g), and results in a regeneration of OHg. This partly compensates for the removal of OHg by direct phase transfer into the cloud and may have important implications regarding the oxidising capacity of the marine boundary layer.

Night-time peroxy radical chemistry in the remote marine boundary layer over the Southern Ocean

1996 ◽  
Vol 23 (5) ◽  
pp. 535-538 ◽  
Author(s):  
Paul S. Monks ◽  
Lucy J. Carpenter ◽  
Smart A. Penkett ◽  
Gregory P. Ayers
Keyword(s):  
Boundary Layer ◽  
Southern Ocean ◽  
Marine Boundary Layer ◽  
Peroxy Radical ◽  
Night Time ◽  
Radical Chemistry
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