scholarly journals Diurnal variability, photochemical production and loss processes of hydrogen peroxide in the boundary layer over Europe

2019 ◽  
Vol 19 (18) ◽  
pp. 11953-11968
Author(s):  
Horst Fischer ◽  
Raoul Axinte ◽  
Heiko Bozem ◽  
John N. Crowley ◽  
Cheryl Ernest ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Hydrogen Peroxide ◽  
Dry Deposition ◽  
Early Morning ◽  
Residual Layer ◽  
Loss Mechanism ◽  
Diurnal Variability ◽  
Mixing Ratios ◽  
Diel Cycles ◽  
Photochemical Production

Abstract. Hydrogen peroxide (H2O2) plays a significant role in the oxidizing capacity of the atmosphere. It is an efficient oxidant in the liquid phase and serves as a temporary reservoir for the hydroxyl radical (OH), the most important oxidizing agent in the gas phase. Due to its high solubility, removal of H2O2 due to wet and dry deposition is efficient, being a sink of HOx (OH+HO2) radicals. In the continental boundary layer, the H2O2 budget is controlled by photochemistry, transport and deposition processes. Here we use in situ observations of H2O2 and account for chemical source and removal mechanisms to study the interplay between these processes. The data were obtained during five ground-based field campaigns across Europe from 2008 to 2014 and bring together observations in a boreal forest, two mountainous sites in Germany, and coastal sites in Spain and Cyprus. Most campaigns took place in the summer, while the measurements in the south-west of Spain took place in early winter. Diel variations in H2O2 are strongly site-dependent and indicate a significant altitude dependence. While boundary-layer mixing ratios of H2O2 at low-level sites show classical diel cycles with the lowest values in the early morning and maxima around local noon, diel profiles are reversed on mountainous sites due to transport from the nocturnal residual layer and the free troposphere. The concentration of hydrogen peroxide is largely governed by its main precursor, the hydroperoxy radical (HO2), and shows significant anti-correlation with nitrogen oxides (NOx) that remove HO2. A budget calculation indicates that in all campaigns, the noontime photochemical production rate through the self-reaction of HO2 radicals was much larger than photochemical loss due to reaction with OH and photolysis, and that dry deposition is the dominant loss mechanism. Estimated dry deposition velocities varied between approximately 1 and 6 cm s−1, with relatively high values observed during the day in forested regions, indicating enhanced uptake of H2O2 by vegetation. In order to reproduce the change in H2O2 mixing ratios between sunrise and midday, a variable contribution from transport (10 %–100 %) is required to balance net photochemical production and deposition loss. Transport is most likely related to entrainment from the residual layer above the nocturnal boundary layer during the growth of the boundary layer in the morning.

scholarly journals Diurnal variability, photochemical production and loss processes of hydrogen peroxide in the boundary layer over Europe

2018 ◽  
Author(s):  
Horst Fischer ◽  
Raoul Axinte ◽  
Heiko Bozem ◽  
John N. Crowley ◽  
Cheryl Ernest ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Hydrogen Peroxide ◽  
Dry Deposition ◽  
Early Morning ◽  
Residual Layer ◽  
Loss Mechanism ◽  
Diurnal Variability ◽  
Mixing Ratios ◽  
Diel Cycles ◽  
Photochemical Production

Abstract. Hydrogen peroxide (H2O2) plays a significant role in the oxidizing capacity of the atmosphere. It is an efficient oxidant in the liquid phase, and serves as a temporary reservoir for the hydroxyl radical (OH), the most important oxidizing agent in the gas phase. Due to its high solubility, removal of H2O2 due to wet and dry deposition is efficient, being a sink of HOx (OH + HO2) radicals. In the continental boundary layer, the H2O2 budget is controlled by photochemistry, transport and deposition processes. Here we use in-situ observations of H2O2, and account for chemical source and removal mechanisms to study the interplay between these processes. The data were obtained during five ground-based field campaigns across Europe from 2008 to 2014, and bring together observations in a boreal forest, two mountainous sites in Germany, and coastal sites in Spain and Cyprus. Most campaigns took place in the summer, while the measurements in the south-west of Spain took place in early winter. Diel variations in H2O2 are strongly site-dependent and indicate a significant altitude dependence. While boundary layer mixing ratios of H2O2 at low-level sites show classical diel cycles with lowest values in the early morning and maxima around local noon, diel profiles are reversed on mountainous sites due to transport from the nocturnal residual layer and the free troposphere. The concentration of hydrogen peroxide is largely governed by its main precursor, the hydroperoxy radical (HO2), and shows significant anti-correlation with nitrogen oxides (NOx) that remove HO2. A budget calculation indicates that in all campaigns, the noontime photochemical production rate through the self-reaction of HO2 radicals was much larger than photochemical loss due to reaction with OH and photolysis, and that dry deposition is the dominant loss mechanism. Estimated dry deposition velocities varied between approx. 1 and 6 cm/s, with relatively high values observed during the day in forested regions, indicating enhanced uptake of H2O2 by vegetation. In order to reproduce the change in H2O2 mixing ratios between sunrise and midday, a variable contribution from transport (10–100 %) is required to balance net photochemical production and deposition loss. Transport is most likely related to entrainment from the residual layer above the nocturnal boundary layer during the growth of the boundary layer in the morning.

scholarly journals Temporal variability, sources, and sinks of C<sub>1</sub>-C<sub>5</sub> alkyl nitrates in Coastal New England

2009 ◽  
Vol 9 (6) ◽  
pp. 23371-23418 ◽  
Author(s):  
R. S. Russo ◽  
Y. Zhou ◽  
K. B. Haase ◽  
O. W. Wingenter ◽  
E. K. Frinak ◽  
...  
Keyword(s):  
New England ◽  
New Hampshire ◽  
Dry Deposition ◽  
Ambient Air ◽  
Early Morning ◽  
Secondary Source ◽  
Alkyl Nitrates ◽  
Mixing Ratios ◽  
Alkyl Nitrate ◽  
Marine Source

Abstract. Seven C1-C5 alkyl nitrates were measured both on the mainland and off the coast of New Hampshire using gas chromatographic techniques. Five separate data sets will be presented to characterize the seasonal and diurnal trends and the major sources and loss processes of these compounds. In situ measurements were conducted at the University of New Hampshire (UNH) Atmospheric Observing Station at Thompson Farm (TF) located in southeast NH during winter (January–February) and summer (June–August) 2002 and summer (July–August) 2004. The median (±standard deviation) total alkyl nitrate mixing ratio (ΣRONO2) was 25 (±7) in winter and 16 (±14) pptv in summer. Furthermore, daily canister samples collected at midday and later analyzed in the laboratory from January 2004–February 2008 gave median ΣRONO2 of 23 (±8) in winter and 14 (±10) pptv in summer. Alkyl nitrate mixing ratios increased throughout the morning and were highest in the afternoon reflecting mixing of remnant boundary layer air toward the surface and photochemical production during the day. During summers 2002 and 2004, MeONO2 decreased overnight and reached minimum hourly average mixing ratios in the early morning (05:00–07:00 LT). Comparison with wind speed and trace gas (i.e., hydrocarbons, ozone, carbon monoxide, total reactive nitrogen) trends suggested that dry deposition contributed to the early morning MeONO2 minimum which is a previously unaccounted for removal mechanism. The mean dry deposition rate and velocity of MeONO2 was estimated to be −0.5 nmol m−2 hr−1 and 0.13 cm s−1, respectively. Results from ambient air and surface seawater measurements made onboard the NOAA R/V Ronald H. Brown in the Gulf of Maine during the 2002 New England Air Quality Study and from ambient canister samples collected throughout the Great Bay estuary in August 2003 are also presented. Comparisons between the alkyl nitrate trends with anthropogenic and marine source fingerprints and tracers suggest that a marine source of alkyl nitrates is not significant in coastal New England. Given the apparent prominence of a secondary source, comparisons between observed and predicted alkyl nitrate/parent hydrocarbon ratios were made which demonstrated that background mixing ratios have a continuous and prevalent influence on the alkyl nitrate distribution.

scholarly journals Global model simulations of air pollution during the 2003 European heat wave

2010 ◽  
Vol 10 (2) ◽  
pp. 789-815 ◽  
Author(s):  
C. Ordóñez ◽  
N. Elguindi ◽  
O. Stein ◽  
V. Huijnen ◽  
J. Flemming ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Heat Wave ◽  
Dry Deposition ◽  
Horizontal Resolution ◽  
High Reactivity ◽  
Transport Processes ◽  
Meteorological Model ◽  
Mixing Ratios ◽  
Period 2 ◽  
Meteorological Features

Abstract. Three global Chemistry Transport Models – MOZART, MOCAGE, and TM5 – as well as MOZART coupled to the IFS meteorological model including assimilation of ozone (O3) and carbon monoxide (CO) satellite column retrievals, have been compared to surface measurements and MOZAIC vertical profiles in the troposphere over Western/Central Europe for summer 2003. The models reproduce the meteorological features and enhancement of pollution during the period 2–14 August, but not fully the ozone and CO mixing ratios measured during that episode. Modified normalised mean biases are around −25% (except ~5% for MOCAGE) in the case of ozone and from −80% to −30% for CO in the boundary layer above Frankfurt. The coupling and assimilation of CO columns from MOPITT overcomes some of the deficiencies in the treatment of transport, chemistry and emissions in MOZART, reducing the negative biases to around 20%. The high reactivity and small dry deposition velocities in MOCAGE seem to be responsible for the overestimation of O3 in this model. Results from sensitivity simulations indicate that an increase of the horizontal resolution to around 1°×1° and potential uncertainties in European anthropogenic emissions or in long-range transport of pollution cannot completely account for the underestimation of CO and O3 found for most models. A process-oriented TM5 sensitivity simulation where soil wetness was reduced results in a decrease in dry deposition fluxes and a subsequent ozone increase larger than the ozone changes due to the previous sensitivity runs. However this latest simulation still underestimates ozone during the heat wave and overestimates it outside that period. Most probably, a combination of the mentioned factors together with underrepresented biogenic emissions in the models, uncertainties in the modelling of vertical/horizontal transport processes in the proximity of the boundary layer as well as limitations of the chemistry schemes are responsible for the underestimation of ozone (overestimation in the case of MOCAGE) and CO found in the models during this extreme pollution event.

scholarly journals A climatological view of the vertical stratification of RH, O<sub>3</sub> and CO within the PBL and at the interface with free troposphere as seen by IAGOS aircraft and ozonesondes at northern mid-latitudes over 1994–2016

2018 ◽  
Author(s):  
Hervé Petetin ◽  
Bastien Sauvage ◽  
Herman G. J. Smit ◽  
François Gheusi ◽  
Fabienne Lohou ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Potential Temperature ◽  
Vertical Stratification ◽  
Vertical Profiles ◽  
Free Troposphere ◽  
Diurnal Variability ◽  
Vertical Coordinate ◽  
Mixing Ratios ◽  
Seasonal And Diurnal Variations ◽  
Individual Profiles

Abstract. This paper investigates in an innovative way the climatological vertical stratification of relative humidity (RH) and ozone (O3) and carbon monoxide (CO) mixing ratios within the planetary boundary layer (PBL) and at the interface with the free troposphere (FT). The climatology includes all vertical profiles available at northern mid-latitudes over the period 1994–2016 in both IAGOS (In-service Aircraft for a Global Observing System) and WOUDC (World Ozone and Ultraviolet Radiation Data Centre) databases, which represents more than 90,000 vertical profiles. For all individual profiles, apart from the specific case of surface-based temperature inversions (SBIs), the PBL height is estimated following the elevated temperature inversion (EI) method. Several features of both SBIs and EIs are analysed, including their diurnal and seasonal variations. Based on these PBL height estimates (denoted h), the original approach introduced in this paper consists in building a so-called PBL-referenced vertical distribution of O3, CO and RH by averaging all individual profiles beforehand expressed as a function of z/h rather than z (with z the altitude). Using this vertical coordinate system allows to highlight the features existing at the PBL-FT interface that would have been smoothed otherwise. Results demonstrate that the frequently assumed well-mixed PBL remains an exception for both chemical species. Within the PBL, CO profiles are characterized by a mean vertical stratification (here defined as the standard deviation of the CO profile between the surface and the PBL top, normalized by the mean) of 11 %, with moderate seasonal and diurnal variations. A higher vertical stratification is observed for O3 mixing ratios (18 %), with stronger seasonal and diurnal variability (from ~ 10 % in spring/summer midday/afternoon to ~ 25 % in winter/fall night). This vertical stratification is distributed heterogeneously in the PBL with stronger vertical gradients observed at both the surface (due to dry deposition and titration by NO for O3; and due to surface emissions for CO) and the PBL-FT interface. These gradients vary with the season from lowest values in summer to highest ones in winter. Contrary to CO, the O3 vertical stratification was found to vary with the surface potential temperature following an interesting bell shape with weakest stratification for both lowest (typically negative) and highest temperatures, which could be due to a much lower O3 dry deposition under the presence of snow. Therefore, results demonstrate that EIs act as a geophysical interface separating air masses of distinct chemical composition and/or chemical regime. This is further supported by the analysis of the correlation of O3 and CO mixing ratios between the different altitude levels in the PBL and FT (the so-called vertical autocorrelation). Results indeed highlight lower correlations apart from the PBL-FT interface and higher correlations within each of the two atmospheric compartments (PBL and FT).

scholarly journals Temporal variability, sources, and sinks of C<sub>1</sub>-C<sub>5</sub> alkyl nitrates in coastal New England

2010 ◽  
Vol 10 (4) ◽  
pp. 1865-1883 ◽  
Author(s):  
R. S. Russo ◽  
Y. Zhou ◽  
K. B. Haase ◽  
O. W. Wingenter ◽  
E. K. Frinak ◽  
...  
Keyword(s):  
New England ◽  
New Hampshire ◽  
Dry Deposition ◽  
Gulf Of Maine ◽  
Ambient Air ◽  
Early Morning ◽  
Secondary Source ◽  
Alkyl Nitrates ◽  
Mixing Ratios ◽  
Alkyl Nitrate

Abstract. Seven C1-C5 alkyl nitrates were measured both on the mainland and off the coast of New Hampshire using gas chromatographic techniques. Five separate data sets are presented to characterize the seasonal and diurnal trends and the major sources and loss processes of these compounds. Based on in situ measurements conducted at the University of New Hampshire (UNH) Atmospheric Observing Station at Thompson Farm (TF) located in southeast NH during winter (January–February) 2002, summer (June–August) 2002, summer (July–August) 2004, and on daily canister samples collected at midday from January 2004–February 2008, the median total alkyl nitrate mixing ratio (ΣRONO2) was 23–25 pptv in winter and 14–16 pptv in summer. During summers 2002 and 2004, MeONO2 decreased overnight and reached minimum hourly average mixing ratios in the early morning. Comparison with wind speed and trace gas trends suggested that dry deposition contributed to the early morning MeONO2 minimum which is a previously unaccounted for removal mechanism. The mean dry deposition rate and velocity of MeONO2 was estimated to be −0.5 nmol m−2 hr−1 and 0.13 cm s−1, respectively. Results from ambient air and surface seawater measurements made onboard the NOAA R/V Ronald H. Brown in the Gulf of Maine during the 2002 New England Air Quality Study and from ambient canister samples collected throughout the Great Bay estuary in August 2003 are also presented. Comparisons between the alkyl nitrate trends with anthropogenic and marine tracers suggest that a marine source of alkyl nitrates is not significant in coastal New England. Given the apparent prominence of a secondary source, comparisons between observed and predicted alkyl nitrate/parent hydrocarbon ratios were made which demonstrated that background mixing ratios have a continuous and prevalent influence on the alkyl nitrate distribution.

scholarly journals New insights in the global cycle of acetonitrile: release from theocean and dry deposition in the tropical savanna of Venezuela

2004 ◽  
Vol 4 (1) ◽  
pp. 275-280 ◽  
Author(s):  
E. Sanhueza ◽  
R. Holzinger ◽  
B. Kleiss ◽  
L. Donoso ◽  
P. J. Crutzen
Keyword(s):  
Boundary Layer ◽  
Biomass Burning ◽  
Dry Deposition ◽  
Mixed Boundary ◽  
Deposition Velocity ◽  
Caribbean Sea ◽  
Proton Transfer Reaction ◽  
Wet Season ◽  
Mixing Ratios ◽  
The Caribbean

Abstract. Using the proton transfer reaction mass spectrometry (PTR-MS) technique, acetonitrile was measured during the wet season in a Venezuelan woodland savanna. The site was located downwind of the Caribbean Sea and no biomass burning events were observed in the region. High boundary layer concentrations of 211±36pmol/mol (median, ±standard deviation) were observed during daytime in the well mixed boundary layer, which is about 60pmol/mol above background concentrations recently measured over the Mediterranean Sea and the Pacific Ocean. Most likely acetonitrile is released from the warm waters of the Caribbean Sea thereby enhancing mixing ratios over Venezuela. Acetonitrile concentrations will probably still be much higher in biomass burning plumes, however, the general suitability of acetonitrile as a biomass burning marker should be treated with care. During nights, acetonitrile dropped to levels typically around 120pmol/mol, which is consistent with a dry deposition velocity of 0.14cm/s when a nocturnal boundary layer height of 100m is assumed.

scholarly journals Surface and boundary layer exchanges of volatile organic compounds, nitrogen oxides and ozone during the GABRIEL campaign

2008 ◽  
Vol 8 (20) ◽  
pp. 6223-6243 ◽  
Author(s):  
L. Ganzeveld ◽  
G. Eerdekens ◽  
G. Feig ◽  
H. Fischer ◽  
H. Harder ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Residual Layer ◽  
Oxidation Products ◽  
Emission Flux ◽  
Mixing Ratios ◽  
Volatile Organic ◽  
Isoprene Oxidation ◽  
Isoprene Oxidation Products

Abstract. We present an evaluation of sources, sinks and turbulent transport of nitrogen oxides, ozone and volatile organic compounds (VOC) in the boundary layer over French Guyana and Suriname during the October 2005 GABRIEL campaign by simulating observations with a single-column chemistry and climate model (SCM) along a zonal transect. Simulated concentrations of O3 and NO as well as NO2 photolysis rates over the forest agree well with observations when a small soil-biogenic NO emission flux was applied. This suggests that the photochemical conditions observed during GABRIEL reflect a pristine tropical low-NOx regime. The SCM uses a compensation point approach to simulate nocturnal deposition and daytime emissions of acetone and methanol and produces daytime boundary layer mixing ratios in reasonable agreement with observations. The area average isoprene emission flux, inferred from the observed isoprene mixing ratios and boundary layer height, is about half the flux simulated with commonly applied emission algorithms. The SCM nevertheless simulates too high isoprene mixing ratios, whereas hydroxyl concentrations are strongly underestimated compared to observations, which can at least partly explain the discrepancy. Furthermore, the model substantially overestimates the isoprene oxidation products methlyl vinyl ketone (MVK) and methacrolein (MACR) partly due to a simulated nocturnal increase due to isoprene oxidation. This increase is most prominent in the residual layer whereas in the nocturnal inversion layer we simulate a decrease in MVK and MACR mixing ratios, assuming efficient removal of MVK and MACR. Entrainment of residual layer air masses, which are enhanced in MVK and MACR and other isoprene oxidation products, into the growing boundary layer poses an additional sink for OH which is thus not available for isoprene oxidation. Based on these findings, we suggest pursuing measurements of the tropical residual layer chemistry with a focus on the nocturnal depletion of isoprene and its oxidation products.

Sign in / Sign up

Export Citation Format

Share Document