scholarly journals Measurement of atmospheric nitrous acid at Blodgett Forest during BEARPEX2007

2010 ◽  
Vol 10 (3) ◽  
pp. 7383-7419 ◽  
Author(s):  
X. Ren ◽  
H. Gao ◽  
X. Zhou ◽  
J. D. Crounse ◽  
P. O. Wennberg ◽  
...  
Keyword(s):  
Nitrous Acid ◽  
Chemical Ionization ◽  
Lower Troposphere ◽  
Late Summer ◽  
Atmospheric Oxidation ◽  
Ionization Mass ◽  
Oxidation Processes ◽  
Highly Sensitive ◽  
Good Agreement

Abstract. Nitrous acid (HONO) is an important precursor of the hydroxyl radical (OH) in the lower troposphere. Understanding HONO chemistry, particularly its sources and contribution to HOx (=OH+HO2) production, is very important for understanding atmospheric oxidation processes. A highly sensitive instrument for detecting atmospheric HONO based on aqueous long path absorption photometry (LOPAP) was deployed in the Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX) at Blodgett Forest, California in late summer 2007. The median diurnal variation shows minimum HONO levels of about 20–30 pptv during the day and maximum levels of about 60–70 pptv at night, a diurnal pattern quite different from the results at various other forested sites. Measured HONO/NO2 ratios for a 24-h period ranged from 0.05 to 0.13 with a mean ratio of 0.07. Speciation of reactive nitrogen compounds (NOy) indicates that HONO accounted for only ~3% of total NOy. However, due to the fast HONO loss through photolysis, a strong HONO source (1.59 ppbv day−1) existed in this environment in order to sustain the observed HONO levels, indicating the significant role of HONO in NOy cycling. The LOPAP HONO measurements were compared to the HONO measurements made with a Chemical Ionization Mass Spectrometer (CIMS) over a three-day period. Good agreement was obtained between the measurements from the two different techniques. Using the expansive suite of photochemical and meteorological measurements, the contribution of HONO photolysis to HOx budget was calculated to be relatively small (6%) compared to results from other forested sites. The lower HONO mixing ratio and thus its smaller contribution to HOx production are attributed to the unique meteorological conditions and low acid precipitation at Blodgett Forest. Further studies of HONO in this kind of environment are needed to test this hypothesis and to improve our understanding of atmospheric oxidation and nitrogen budget.

scholarly journals Measurement of atmospheric nitrous acid at Bodgett Forest during BEARPEX2007

2010 ◽  
Vol 10 (13) ◽  
pp. 6283-6294 ◽  
Author(s):  
X. Ren ◽  
H. Gao ◽  
X. Zhou ◽  
J. D. Crounse ◽  
P. O. Wennberg ◽  
...  
Keyword(s):  
Nitrous Acid ◽  
Chemical Ionization ◽  
Lower Troposphere ◽  
Late Summer ◽  
Atmospheric Oxidation ◽  
Ionization Mass ◽  
Wet Chemistry ◽  
Highly Sensitive ◽  
Good Agreement

Abstract. Nitrous acid (HONO) is an important precursor of the hydroxyl radical (OH) in the lower troposphere. Understanding HONO chemistry, particularly its sources and contribution to HOx (=OH+HO2) production, is very important for understanding atmospheric oxidation processes. A highly sensitive instrument for detecting atmospheric HONO based on wet chemistry followed by liquid waveguide long path absorption photometry was deployed in the Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX) at Blodgett Forest, California in late summer 2007. The median diurnal variation shows minimum HONO levels of about 20–30 pptv during the day and maximum levels of about 60–70 pptv at night, a diurnal pattern quite different from the results at various other forested sites. Measured HONO/NO2 ratios for a 24-h period ranged from 0.05 to 0.13 with a mean ratio of 0.07. Speciation of reactive nitrogen compounds (NOy) indicates that HONO accounted for only ~3% of total NOy. However, due to the fast HONO loss through photolysis, a strong HONO source (1.59 ppbv day−1) existed in this environment in order to sustain the observed HONO levels, indicating the significant role of HONO in NOy cycling. The wet chemistry HONO measurements were compared to the HONO measurements made with a Chemical Ionization Mass Spectrometer (CIMS) over a three-day period. Good agreement was obtained between the measurements from the two different techniques. Using the expansive suite of photochemical and meteorological measurements, the contribution of HONO photolysis to HOx budget was calculated to be relatively small (6%) compared to results from other forested sites. The lower HONO mixing ratio and thus its smaller contribution to HOx production are attributed to the unique meteorological conditions and low acid precipitation at Blodgett Forest. Further studies of HONO in this kind of environment are needed to test this hypothesis and to improve our understanding of atmospheric oxidation and nitrogen budget.

scholarly journals Ternary homogeneous nucleation of H<sub>2</sub>SO<sub>4</sub>, NH<sub>3</sub>, and H<sub>2</sub>O under conditions relevant to the lower troposphere

2011 ◽  
Vol 11 (10) ◽  
pp. 4755-4766 ◽  
Author(s):  
D. R. Benson ◽  
J. H. Yu ◽  
A. Markovich ◽  
S.-H. Lee
Keyword(s):  
Homogeneous Nucleation ◽  
Chemical Ionization ◽  
Lower Troposphere ◽  
Global Scale ◽  
Ionization Mass ◽  
Aerosol Formation ◽  
Laboratory Measurements ◽  
Mass Spectrometers ◽  
Water Condensation ◽  
Atmospheric Observations

Abstract. Ternary homogeneous nucleation (THN) of H2SO4, NH3 and H2O has been used to explain new particle formation in various atmospheric regions, yet laboratory measurements of THN have failed to reproduce atmospheric observations. Here, we report first laboratory observations of THN made under conditions relevant to the lower troposphere ([H2SO4] of 106–107 cm−3, [NH3] of 0.08–20 ppbv, and a temperature of 288 K). Our observations show that NH3 can enhance atmospheric H2SO4 aerosol nucleation and the enhancement factor (EF) in nucleation rate (J) due to NH3 (the ratio of J measured with vs. without NH3) increases linearly with increasing [NH3] and increases with decreasing [H2SO4] and RH. Two chemical ionization mass spectrometers (CIMS) are used to measure [H2SO4] and [NH3], as well as possible impurities of amines in the nucleation system. Aerosol number concentrations are measured with a water condensation counter (CPC, TSI 3786). The slopes of Log J vs. Log [H2SO4], Log J vs. Log RH, and Log J vs. Log [NH3] are 3–5, 1–4, and 1, respectively. These slopes and the threshold of [H2SO4] required for the unity nucleation vary only fractionally in the presence and absence of NH3. These observations can be used to improve aerosol nucleation models to assess how man-made SO2 and NH3 affect aerosol formation and CCN production at the global scale.

Photo-Induced Heterogeneous Chemistry of Reactive Species on Aerosol Surfaces: Using Photo-Fragmentation Laser Induced Fluorescence for the Measurement of Nitrous Acid Production from Titanium Dioxide Aerosols

2020 ◽  
Author(s):  
Joanna Dyson ◽  
Graham Boustead ◽  
Lauren Fleming ◽  
Mark Blitz ◽  
Daniel Stone ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Nitrous Acid ◽  
Laser Induced Fluorescence ◽  
Heterogeneous Chemistry ◽  
Sources And Sinks ◽  
Atmospheric Species ◽  
Highly Sensitive ◽  
Secondary Pollutants ◽  
Reactive Uptake Coefficient

&lt;p&gt;The hydroxyl radical (OH) is the main oxidant in the troposphere and is vitally important for its role in the removal of greenhouse gases such as methane from the atmosphere. Moreover, the OH radical also has a role in the formation of secondary pollutants such as tropospheric ozone and secondary organic aerosols (SOAs), formed via the oxidation of volatile organic compounds (VOCs). Understanding the sources and sinks of OH within the atmosphere is therefore crucial in order to fully understand the concentration and distribution of trace atmospheric species associated with climate change and poor air quality.&lt;/p&gt;&lt;p&gt;In polluted environments the dominant source of OH to initiate oxidation is the photolysis of nitrous acid (HONO). Current atmospheric chemistry models underestimate the concentration of HONO indicating a potential missing tropospheric source of HONO. There is a large uncertainty in the production of HONO from the contribution and role of aerosols and heterogeneous chemistry both under light and dark conditions.&lt;/p&gt;&lt;p&gt;In order to investigate the missing source of HONO from illuminated aerosols and determine its atmospheric relevance, a photo-fragmentation laser induced fluorescence (PF-LIF) instrument coupled to an aerosol flow tube system has been constructed. The PF-LIF instrument provides a highly sensitive measurement of HONO by fragmenting it into OH which is then detected in a low pressure cell by LIF. The aim of this system is to measure the rate of production of HONO from illuminated aerosol surfaces.&lt;/p&gt;&lt;p&gt;We will present an overview of the PF-LIF instrument and results from experiments investigating the reactive uptake of NO&lt;sub&gt;2&lt;/sub&gt; by TiO&lt;sub&gt;2&lt;/sub&gt; aerosols to produce HONO. The change in the reactive uptake coefficient as a function of NO&lt;sub&gt;2&lt;/sub&gt; concentration and the dependence of HONO production on relative humidity and light intensity will also be discussed.&amp;#160; &amp;#160;&lt;/p&gt;

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