scholarly journals Measurements of HONO during BAQS-Met

2010 ◽  
Vol 10 (24) ◽  
pp. 12285-12293 ◽  
Author(s):  
J. J. B. Wentzell ◽  
C. L. Schiller ◽  
G. W. Harris
Keyword(s):  
Gas Phase ◽  
Water Vapour ◽  
Nitrous Acid ◽  
Meteorological Parameters ◽  
Border Region ◽  
Night Time ◽  
Mixing Ratios ◽  
Oxidation Chemistry ◽  
Absorption Photometer ◽  
Shed Light

Abstract. Measurements of nitrous acid (HONO) were performed as part of the 2007 Border Air Quality and Meteorology Study (BAQS-Met) at the Harrow, Ontario, Canada supersite between 20 June and 10 July 2007. Nitrous acid is an important precursor of the hydroxyl radical and understanding its chemistry is important to understanding daytime oxidation chemistry. The HONO measurements were made using a custom built Long Path Absorption Photometer (LOPAP). The goal of this work was to shed light on sources of daytime HONO in the border region. During the course of the campaign HONO mixing ratios consistently exceeded expected daytime values by more than a factor of 6. Mean daytime mixing ratios of 61 pptv were observed. While HONO decay began at sunrise, minimum HONO values were measured during the late afternoon. There was little difference between the daytime (mean = 1.5%) and night-time (mean = 1.7%) ratios of HONO/NO2, thus there was a very strong daytime source of HONO which is consistent with other recent studies. Correlations of daytime HONO production with a variety of chemical and meteorological parameters indicate that production is dependent on UV radiation, NO2 and water vapour but is not consistent with a simple gas phase process. Apparent rate constants for the production of HONO from photolyticaly excited NO2 and water vapour vary from 2.8–7.8×10−13 cm3 molec−1 s−1, during the campaign. These results appear to be consistent with the heterogeneous conversion of NO2 enhanced by photo-excitation.

scholarly journals Measurements of HONO during BAQS-Met

2010 ◽  
Vol 10 (6) ◽  
pp. 15295-15323 ◽  
Author(s):  
J. J. B. Wentzell ◽  
C. L. Schiller ◽  
G. W. Harris
Keyword(s):  
Gas Phase ◽  
Water Vapour ◽  
Nitrous Acid ◽  
Meteorological Parameters ◽  
Border Region ◽  
Night Time ◽  
Mixing Ratios ◽  
Oxidation Chemistry ◽  
Absorption Photometer ◽  
Shed Light

Abstract. Measurements of nitrous acid (HONO) were performed as part of the 2007 Border Air Quality and Meteorology Study (BAQS-Met) at the Harrow Ontario supersite between 20 June and 10 July 2007. Nitrous acid is an important precursor of the hydroxy radical and understanding its chemistry is important to understanding daytime oxidation chemistry. The HONO measurements were made using a custom built Long Path Absorption Photometer (LOPAP). The goal of this work was to shed light on sources of daytime HONO in the border region. During the course of the campaign HONO mixing ratios consistently exceeded expected daytime values by as much as a factor of 6. Mean daytime concentrations of 61 pptv were observed. While HONO decay began at sunrise, minimum HONO values were not measured until the late afternoon. There was little difference between the daytime (mean=1.5%) and night-time (mean=1.7%) ratios of HONO/NO2. Thus there was a very strong daytime source of HONO which is consistent with other recent studies. Correlations of daytime HONO production with a variety of chemical and meteorological parameters indicate that production is dependent on UV radiation, NO2 and water vapour but is not consistent with a simple gas phase process. Apparent rate constants for the production of HONO from photolyticly excited NO2 and water vapour vary from 2.8–7.8×10−3 molec−1 s−1, during the campaign.

scholarly journals Modeling nitrous acid and its impact on ozone and hydroxyl radical during the Texas Air Quality Study 2006

2012 ◽  
Vol 12 (2) ◽  
pp. 5851-5880 ◽  
Author(s):  
B. H. Czader ◽  
B. Rappenglück ◽  
P. Percell ◽  
D. W. Byun ◽  
F. Ngan ◽  
...  
Keyword(s):  
Air Quality ◽  
Hydroxyl Radical ◽  
Gas Phase ◽  
Nitrous Acid ◽  
Organic Materials ◽  
Optical Absorption Spectroscopy ◽  
Ozone Formation ◽  
Mixing Ratios ◽  
Quality Study ◽  
Mist Chamber

Abstract. Nitrous acid (HONO) mixing ratios for the Houston metropolitan area were simulated with the Community Multiscale Air Quality (CMAQ) model for an episode during the Texas Air Quality Study (TexAQS) II in August/September 2006 and compared to in-situ MC/IC (mist-chamber/ion chromatograph) and long path DOAS (Differential Optical Absorption Spectroscopy) measurements at three different altitudes. Several HONO sources were accounted for in simulations, such as gas phase formation, direct emissions, nitrogen dioxide (NO2*) hydrolysis, photo-induced formation from excited NO2* and photo-induced conversion of NO2 into HONO on surfaces covered with organic materials. Compared to the gas-phase HONO formation there was about a tenfold increase in HONO mixing ratios when additional HONO sources were taken into account, which improved the correlation between modeled and measured values. Concentrations of HONO simulated with only gas phase chemistry did not change with altitude, while measured HONO concentrations decrease with height. A trend of decreasing HONO concentration with altitude was well captured with CMAQ predicted concentrations when heterogeneous chemistry and photolytic sources of HONO were taken into account. Heterogeneous HONO production mainly accelerated morning ozone formation, albeit slightly. Also HONO formation from excited NO2 only slightly affected HONO and ozone (O3) concentrations. Photo-induced conversion of NO2 into HONO on surfaces covered with organic materials turned out to be a strong source of daytime HONO. Since HONO immediately photo-dissociates during daytime its ambient mixing ratios were only marginally altered (up to 0.5 ppbv), but significant increase in the hydroxyl radical (OH) and ozone concentration was obtained. In contrast to heterogeneous HONO formation that mainly accelerated morning ozone formation, inclusion of photo-induced surface chemistry influenced ozone throughout the day.

scholarly journals Quantification of the unknown HONO daytime source and its relation to NO<sub>2</sub>

2011 ◽  
Vol 11 (5) ◽  
pp. 15119-15155 ◽  
Author(s):  
M. Sörgel ◽  
E. Regelin ◽  
H. Bozem ◽  
J.-M. Diesch ◽  
F. Drewnick ◽  
...  
Keyword(s):  
Nitrogen Oxides ◽  
Gas Phase ◽  
Water Vapour ◽  
Field Data ◽  
Mixing Ratios ◽  
Photostationary State ◽  
Conversion Frequency ◽  
Photolysis Frequency ◽  
Electronically Excited ◽  
Measured Field

Abstract. During the DOMINO (Diel Oxidant Mechanism In relation to Nitrogen Oxides) campaign in southwest Spain we measured simultaneously all quantities necessary to calculate a photostationary state for HONO in the gas phase. These quantities comprise the concentrations of OH, NO, and HONO and the photolysis frequency of NO2, j(NO2) as a proxy for j(HONO). This allowed us to calculate values of the unknown HONO daytime source. This unknown HONO source, normalized by NO2 mixing ratios and expressed as a conversion frequency (% h−1), showed a clear dependence on j(NO2) with values up to 43 % h−1 at noon. We compared our unknown HONO source with values calculated from the measured field data for two recently proposed processes, the light-induced NO2 conversion on soot surfaces and the reaction of electronically excited NO2* with water vapour, with the result that these two reactions normally contributed less than 10 % (<1 % NO2 + soot + hν; and <10 % NO2* + H2O) to our unknown HONO daytime source. OH production from HONO photolysis was found to be larger (by 20 %) than the "classical" OH formation from ozone photolysis (O(1D)) integrated over the day.

scholarly journals Quantification of the unknown HONO daytime source and its relation to NO<sub>2</sub>

2011 ◽  
Vol 11 (20) ◽  
pp. 10433-10447 ◽  
Author(s):  
M. Sörgel ◽  
E. Regelin ◽  
H. Bozem ◽  
J.-M. Diesch ◽  
F. Drewnick ◽  
...  
Keyword(s):  
Nitrogen Oxides ◽  
Gas Phase ◽  
Water Vapour ◽  
Field Data ◽  
Mixing Ratios ◽  
Photostationary State ◽  
Conversion Frequency ◽  
Photolysis Frequency ◽  
Electronically Excited ◽  
Measured Field

Abstract. During the DOMINO (Diel Oxidant Mechanism In relation to Nitrogen Oxides) campaign in southwest Spain we measured simultaneously all quantities necessary to calculate a photostationary state for HONO in the gas phase. These quantities comprise the concentrations of OH, NO, and HONO and the photolysis frequency of NO2, j(NO2) as a proxy for j(HONO). This allowed us to calculate values of the unknown HONO daytime source. This unknown HONO source, normalized by NO2 mixing ratios and expressed as a conversion frequency (% h−1), showed a clear dependence on j(NO2) with values up to 43% h−1 at noon. We compared our unknown HONO source with values calculated from the measured field data for two recently proposed processes, the light-induced NO2 conversion on soot surfaces and the reaction of electronically excited NO2* with water vapour, with the result that these two reactions normally contributed less than 10% (<1% NO2 + soot + hν; and <10% NO2* + H2O) to our unknown HONO daytime source. OH production from HONO photolysis was found to be larger (by 20%) than the "classical" OH formation from ozone photolysis (O(1D)) integrated over the day.

scholarly journals WRF-chem model predictions of the regional impacts of N<sub>2</sub>O<sub>5</sub> heterogeneous processes on nighttime chemistry over north-western Europe

2014 ◽  
Vol 14 (14) ◽  
pp. 20883-20943 ◽  
Author(s):  
D. Lowe ◽  
S. Archer-Nicholls ◽  
W. Morgan ◽  
J. Allan ◽  
S. Utembe ◽  
...  
Keyword(s):  
Gas Phase ◽  
Western Europe ◽  
Oxidative Capacity ◽  
Negative Influence ◽  
Heterogeneous Chemistry ◽  
Night Time ◽  
Regional Modelling ◽  
Mixing Ratios ◽  
Heterogeneous Processes ◽  
North Western

Abstract. Chemical modelling studies have been conducted over north-western Europe in summer conditions, showing that night-time dinitrogen pentoxide (N2O5) heterogeneous reactive uptake is important regionally in modulating particulate nitrate and has a modest influence on oxidative chemistry. Results from WRF-Chem model simulations, run with a detailed volatile organic compound (VOC) gas-phase chemistry scheme and the MOSAIC sectional aerosol scheme, were compared with a series of airborne gas and particulate measurements made over the UK in July 2010. Modelled mixing ratios of key gas-phase species were reasonably accurate (correlations with measurements of 0.7–0.9 for NO2 and O3). However modelled loadings of particulate species were less accurate (correlation with measurements for particulate sulphate and ammonium were between 0.0–0.6). Sulphate mass loadings were particularly low (modelled means of 0.5–0.7 μg kg−1air, compared with measurements of 1.0–1.5 μg kg−1air). Two flights from the campaign were used as testcases – one with low relative humidity (RH) (60–70%), the other with high RH (80–90%). N2O5 heterogeneous chemistry was found to not important in the low RH testcase; but in the high RH testcase it had a strong effect, and significantly improved the agreement between modelled and measured NO3 and N2O5. When the model failed to capture atmospheric RH correctly, the modelled NO3 and N2O5 mixing ratios for these flights differed significantly from the measurements. This demonstrates that, for regional modelling which involves heterogeneous processes, it is essential to capture the ambient temperature and water vapour profiles. The night-time NO3 oxidation of VOCs across the whole region was found to be × 100–300 slower than the daytime OH oxidation of these compounds. The difference in contribution was less for alkenes (× 80), and comparable for DMS. However the suppression of NO3 mixing ratios across the domain by N2O5 heterogeneous chemistry has only a very slight, negative, influence on this oxidative capacity. The influence on regional particulate nitrate mass loadings is stronger. Night-time N2O5 heterogeneous chemistry maintains the production of particulate nitrate within polluted regions: when this process is taken into consideration, the daytime peak (for the 95th percentile) of PM10 nitrate mass loadings remains around 5.6 μg kg−1air, but the nighttime minimum increases from 3.5 to 4.6 μg kg−1air. The sustaining of higher particulate mass loadings through the night by this process improves model skill at matching measured aerosol nitrate diurnal cycles, and will negatively impact on regional air quality, requiring this process to be included in regional models.

scholarly journals A portable, robust, stable and tunable calibration source for gas-phase nitrous acid (HONO)

2020 ◽  
Author(s):  
Melodie Lao ◽  
Leigh R. Crilley ◽  
Leyla Salehpoor ◽  
Teles C. Furlani ◽  
Ilann Bourgeois ◽  
...  
Keyword(s):  
Gas Phase ◽  
Nitrous Acid ◽  
Calibration Source ◽  
Mixing Ratios ◽  
Lab Experiments ◽  
Outdoor Environments ◽  
Indoor And Outdoor Environments ◽  
Relevant Range ◽  
Indoor And Outdoor ◽  
Atmospherically Relevant

Abstract. Atmospheric HONO mixing ratios in indoor and outdoor environments span a range of less than a few parts per trillion by volume (pptv) up to tens of parts per billion by volume (ppbv) in combustion plumes. Previous HONO calibration sources have utilized proton transfer acid displacement from nitrite salts or solutions, with output that ranges from tens to thousands of ppbv. Instrument calibrations have thus required large dilution flows to obtain atmospherically relevant mixing ratios. Here we present a simple universal source to reach very low HONO calibration mixing ratios using a nitrite-coated reaction device with the addition of humid air and/or HCl from a permeation device. The calibration source developed in this work can generate HONO across the atmospherically relevant range and has high purity (90–99 %), reproducibility, and tunability. Mixing ratios at the tens of pptv level are easily reached with reasonable dilution flows. The calibration source can be assembled to start producing stable HONO mixing ratios (RSE ≤ 2 %) within two hours, with output concentrations varying ≤ 25 % following simulated transport or complete disassembly of the instrument, and ≤ 10 % under ideal conditions. The simplicity of this source makes it highly versatile for field and lab experiments. The platform facilitates a new level of accuracy in established instrumentation, as well as intercomparison studies to identify systematic HONO measurement bias and interferences.

scholarly journals Modeling nitrous acid and its impact on ozone and hydroxyl radical during the Texas Air Quality Study 2006

2012 ◽  
Vol 12 (15) ◽  
pp. 6939-6951 ◽  
Author(s):  
B. H. Czader ◽  
B. Rappenglück ◽  
P. Percell ◽  
D. W. Byun ◽  
F. Ngan ◽  
...  
Keyword(s):  
Air Quality ◽  
Hydroxyl Radical ◽  
Gas Phase ◽  
Nitrous Acid ◽  
Organic Materials ◽  
Optical Absorption Spectroscopy ◽  
Ozone Formation ◽  
Mixing Ratios ◽  
Quality Study ◽  
Mist Chamber

Abstract. Nitrous acid (HONO) mixing ratios for the Houston metropolitan area were simulated with the Community Multiscale Air Quality (CMAQ) Model for an episode during the Texas Air Quality Study (TexAQS) II in August/September 2006 and compared to in-situ MC/IC (mist-chamber/ion chromatograph) and long path DOAS (Differential Optical Absorption Spectroscopy) measurements at three different altitude ranges. Several HONO sources were accounted for in simulations, such as gas phase formation, direct emissions, nitrogen dioxide (NO2) hydrolysis, photo-induced formation from excited NO2 and photo-induced conversion of NO2 into HONO on surfaces covered with organic materials. Compared to the gas-phase HONO formation there was about a tenfold increase in HONO mixing ratios when additional HONO sources were taken into account, which improved the correlation between modeled and measured values. Concentrations of HONO simulated with only gas phase chemistry did not change with altitude, while measured HONO concentrations decrease with height. A trend of decreasing HONO concentration with altitude was well captured with CMAQ predicted concentrations when heterogeneous chemistry and photolytic sources of HONO were taken into account. Heterogeneous HONO production mainly accelerated morning ozone formation, albeit slightly. Also HONO formation from excited NO2 only slightly affected HONO and ozone (O3) concentrations. Photo-induced conversion of NO2 into HONO on surfaces covered with organic materials turned out to be a strong source of daytime HONO. Since HONO immediately photo-dissociates during daytime its ambient mixing ratios were only marginally altered (up to 0.5 ppbv), but significant increase in the hydroxyl radical (OH) and ozone concentration was obtained. In contrast to heterogeneous HONO formation that mainly accelerated morning ozone formation, inclusion of photo-induced surface chemistry influenced ozone throughout the day.

scholarly journals WRF-Chem model predictions of the regional impacts of N<sub>2</sub>O<sub>5</sub> heterogeneous processes on night-time chemistry over north-western Europe

2015 ◽  
Vol 15 (3) ◽  
pp. 1385-1409 ◽  
Author(s):  
D. Lowe ◽  
S. Archer-Nicholls ◽  
W. Morgan ◽  
J. Allan ◽  
S. Utembe ◽  
...  
Keyword(s):  
Gas Phase ◽  
Western Europe ◽  
Negative Influence ◽  
Test Case ◽  
Heterogeneous Chemistry ◽  
Night Time ◽  
Regional Modelling ◽  
Mixing Ratios ◽  
Heterogeneous Processes ◽  
North Western

Abstract. Chemical modelling studies have been conducted over north-western Europe in summer conditions, showing that night-time dinitrogen pentoxide (N2O5) heterogeneous reactive uptake is important regionally in modulating particulate nitrate and has a~modest influence on oxidative chemistry. Results from Weather Research and Forecasting model with Chemistry (WRF-Chem) model simulations, run with a detailed volatile organic compound (VOC) gas-phase chemistry scheme and the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) sectional aerosol scheme, were compared with a series of airborne gas and particulate measurements made over the UK in July 2010. Modelled mixing ratios of key gas-phase species were reasonably accurate (correlations with measurements of 0.7–0.9 for NO2 and O3). However modelled loadings of particulate species were less accurate (correlation with measurements for particulate sulfate and ammonium were between 0.0 and 0.6). Sulfate mass loadings were particularly low (modelled means of 0.5–0.7 μg kg−1air, compared with measurements of 1.0–1.5 μg kg−1air). Two flights from the campaign were used as test cases – one with low relative humidity (RH) (60–70%), the other with high RH (80–90%). N2O5 heterogeneous chemistry was found to not be important in the low-RH test case; but in the high-RH test case it had a strong effect and significantly improved the agreement between modelled and measured NO3 and N2O5. When the model failed to capture atmospheric RH correctly, the modelled NO3 and N2O5 mixing ratios for these flights differed significantly from the measurements. This demonstrates that, for regional modelling which involves heterogeneous processes, it is essential to capture the ambient temperature and water vapour profiles. The night-time NO3 oxidation of VOCs across the whole region was found to be 100–300 times slower than the daytime OH oxidation of these compounds. The difference in contribution was less for alkenes (× 80) and comparable for dimethylsulfide (DMS). However the suppression of NO3 mixing ratios across the domain by N2O5 heterogeneous chemistry has only a very slight, negative, influence on this oxidative capacity. The influence on regional particulate nitrate mass loadings is stronger. Night-time N2O5 heterogeneous chemistry maintains the production of particulate nitrate within polluted regions: when this process is taken into consideration, the daytime peak (for the 95th percentile) of PM10 nitrate mass loadings remains around 5.6 μg kg−1air, but the night-time minimum increases from 3.5 to 4.6 μg kg−1air. The sustaining of higher particulate mass loadings through the night by this process improves model skill at matching measured aerosol nitrate diurnal cycles and will negatively impact on regional air quality, requiring this process to be included in regional models.

scholarly journals Formaldehyde (HCHO) in air, snow, and interstitial air at Concordia (East Antarctic Plateau) in summer

2015 ◽  
Vol 15 (12) ◽  
pp. 6689-6705 ◽  
Author(s):  
S. Preunkert ◽  
M. Legrand ◽  
M. M. Frey ◽  
A. Kukui ◽  
J. Savarino ◽  
...  
Keyword(s):  
Gas Phase ◽  
Ambient Air ◽  
Snow Surface ◽  
Antarctic Plateau ◽  
Mixing Ratios ◽  
Emission Fluxes ◽  
Oxidation Chemistry ◽  
First Time ◽  
Phase Production ◽  
Interstitial Air

Abstract. During the 2011/12 and 2012/13 austral summers, HCHO was investigated for the first time in ambient air, snow, and interstitial air at the Concordia site, located near Dome C on the East Antarctic Plateau, by deploying an Aerolaser AL-4021 analyzer. Snow emission fluxes were estimated from vertical gradients of mixing ratios observed at 1 cm and 1 m above the snow surface as well as in interstitial air a few centimeters below the surface and in air just above the snowpack. Typical flux values range between 1 and 2 × 1012 molecules m−2 s−1 at night and 3 and 5 × 1012 molecules m−2 s−1 at noon. Shading experiments suggest that the photochemical HCHO production in the snowpack at Concordia remains negligible compared to temperature-driven air–snow exchanges. At 1 m above the snow surface, the observed mean mixing ratio of 130 pptv and its diurnal cycle characterized by a slight decrease around noon are quite well reproduced by 1-D simulations that include snow emissions and gas-phase methane oxidation chemistry. Simulations indicate that the gas-phase production from CH4 oxidation largely contributes (66%) to the observed HCHO mixing ratios. In addition, HCHO snow emissions account for ~ 30% at night and ~ 10% at noon to the observed HCHO levels.

scholarly journals Formaldehyde (HCHO) in air, snow and interstitial air at Concordia (East Antarctic plateau) in summer

2014 ◽  
Vol 14 (23) ◽  
pp. 32027-32070 ◽  
Author(s):  
S. Preunkert ◽  
M. Legrand ◽  
M. Frey ◽  
A. Kukui ◽  
J. Savarino ◽  
...  
Keyword(s):  
Gas Phase ◽  
Ambient Air ◽  
Snow Surface ◽  
Snow Pack ◽  
Antarctic Plateau ◽  
Mixing Ratios ◽  
Emission Fluxes ◽  
Oxidation Chemistry ◽  
First Time ◽  
Interstitial Air

Abstract. During the 2011/12 and 2012/13 austral summers HCHO was investigated for the first time in ambient air, snow, and interstitial air at the Concordia site located near Dome C on the East Antarctic plateau by deploying an Aerolaser AL-4021 analyser. Snow emission fluxes were estimated from vertical gradients of mixing ratios observed between 1 cm and 1 m above the snow surface as well as between interstitial air a few cm below the surface and in air just above the snow-pack. Typical flux values range between 1 to 2 × 1012 molecules m−2 s−1 at night and 3 to 5 × 1012 molecules m−2 s−1 at noon. Shading experiments suggest that the photochemical HCHO production in the snowpack at Concordia remains negligible compared to temperature-driven air–snow exchanges. At 1 m above the snow surface, the observed mean mixing ratio of 130 pptv and its diurnal cycle characterized by a slight decrease around noon are quite well reproduced by 1-D simulations that include snow emissions and gas phase methane oxidation chemistry.

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