scholarly journals Speciation of OH reactivity above the canopy of an isoprene-dominated forest

2016 ◽  
Author(s):  
J. Kaiser ◽  
K. M. Skog ◽  
K. Baumann ◽  
S. B. Bertman ◽  
S. B. Brown ◽  
...  
Keyword(s):  
Oxidation Products ◽  
Ozone Production ◽  
Biogenic Emissions ◽  
Absolute Value ◽  
Reactive Carbon ◽  
Volatile Organic ◽  
Measurement Suite ◽  
Primary Emissions ◽  
Comprehensive Measurement ◽  
Good Agreement

Abstract. Measurements of OH reactivity, the inverse lifetime of the OH-radical, can provide a top-down estimate of the total amount of reactive carbon in an airmass. Because OH reactivity is tied to the RO2 production rate, the absolute value of OH reactivity has direct implications for ozone production. Additionally, as molecular structure determines volatility, the speciation of reactivity affects the production of secondary organic aerosol (SOA). Several studies have focused on the agreement of measured and calculated or modeled OH reactivity above and within the canopy of isoprene-dominated forests, as well as the relative contributions of volatile organic compounds (VOCs) and oxidized VOCs (OVOCs). Drawing definitive conclusions about the identity of the missing OH reactivity has been limited by the availability of VOC and OVOC measurements. In this work, using a comprehensive measurement suite, we examine the measured and modeled OH reactivity above an isoprene-dominated forest in the South East United States during the 2013 Southern Oxidant and Aerosol Study (SOAS) field campaign. We find good agreement between measured and modeled OH reactivity, with the largest contribution consistently coming from primary biogenic emissions. In contrast, there are small but significant discrepancies in the increase in OH reactivity per isoprene. As the model typically overestimates OVOCs, we do not attribute this discrepancy to unmeasured oxidation products. Instead, we suggest that unmeasured primary emissions may influence the OH reactivity at this site.

scholarly journals Speciation of OH reactivity above the canopy of an isoprene-dominated forest

2016 ◽  
Vol 16 (14) ◽  
pp. 9349-9359 ◽  
Author(s):  
J. Kaiser ◽  
K. M. Skog ◽  
K. Baumann ◽  
S. B. Bertman ◽  
S. B. Brown ◽  
...  
Keyword(s):  
Early Morning ◽  
Oxidation Products ◽  
Biogenic Emissions ◽  
Oh Radical ◽  
Southeast United States ◽  
Reactive Carbon ◽  
Additional Constant ◽  
Measurement Suite ◽  
Primary Emissions ◽  
Comprehensive Measurement

Abstract. Measurements of OH reactivity, the inverse lifetime of the OH radical, can provide a top–down estimate of the total amount of reactive carbon in an air mass. Using a comprehensive measurement suite, we examine the measured and modeled OH reactivity above an isoprene-dominated forest in the southeast United States during the 2013 Southern Oxidant and Aerosol Study (SOAS) field campaign. Measured and modeled species account for the vast majority of average daytime reactivity (80–95 %) and a smaller portion of nighttime and early morning reactivity (68–80 %). The largest contribution to total reactivity consistently comes from primary biogenic emissions, with isoprene contributing ∼  60 % in the afternoon, and ∼  30–40 % at night and monoterpenes contributing ∼  15–25 % at night. By comparing total reactivity to the reactivity stemming from isoprene alone, we find that ∼  20 % of the discrepancy is temporally related to isoprene reactivity, and an additional constant ∼  1 s−1 offset accounts for the remaining portion. The model typically overestimates measured OVOC concentrations, indicating that unmeasured oxidation products are unlikely to influence measured OH reactivity. Instead, we suggest that unmeasured primary emissions may influence the OH reactivity at this site.

scholarly journals Observations of oxidation products above a forest imply biogenic emissions of very reactive compounds

2005 ◽  
Vol 5 (1) ◽  
pp. 67-75 ◽  
Author(s):  
R. Holzinger ◽  
A. Lee ◽  
K. T. Paw ◽  
U. A. H. Goldstein
Keyword(s):  
Ponderosa Pine ◽  
Forest Canopy ◽  
Large Fraction ◽  
Oxidation Products ◽  
Biogenic Emissions ◽  
Central California ◽  
Mixing Ratios ◽  
Volatile Organic ◽  
Current Emission ◽  
Ponderosa Pine Forest

Abstract. Vertical gradients of mixing ratios of volatile organic compounds have been measured in a Ponderosa pine forest in Central California (38.90° N, 120.63° W, 1315m). These measurements reveal large quantities of previously unreported oxidation products of short lived biogenic precursors. The emission of biogenic precursors must be in the range of 13-66µmol m-2h-1 to produce the observed oxidation products. That is 6-30 times the emissions of total monoterpenes observed above the forest canopy on a molar basis. These reactive precursors constitute a large fraction of biogenic emissions at this site, and are not included in current emission inventories. When oxidized by ozone they should efficiently produce secondary aerosol and hydroxyl radicals.

scholarly journals Observations of oxidation products above a forest imply biogenic emissions of very reactive compounds

2004 ◽  
Vol 4 (5) ◽  
pp. 5345-5365 ◽  
Author(s):  
R. Holzinger ◽  
A. Lee ◽  
K. T. Paw U ◽  
A. H. Goldstein
Keyword(s):  
Organic Compounds ◽  
Hydroxyl Radicals ◽  
Forest Canopy ◽  
Oxidation Products ◽  
Biogenic Emissions ◽  
Emission Inventories ◽  
Central California ◽  
Molar Basis ◽  
Volatile Organic ◽  
Current Emission

Abstract. Measurements of volatile organic compounds in a pine forest (Central California, 38.90° N, 120.63° W, 1315 m) reveal large quantities of previously unreported oxidation products of short lived biogenic precursors. The emission of biogenic precursors must be in the range of 13–66 µmol m−2 h−1 to produce the observed oxidation products. That is 6–30 times the emissions of total monoterpenes observed above the forest canopy on a molar basis. These reactive precursors constitute the largest fraction of biogenic emissions at this site, and are not included in current emission inventories. When oxidized by ozone they should efficiently produce secondary aerosol and hydroxyl radicals.

scholarly journals <i>α</i>-Pinene Nitrates: synthesis, yields and atmospheric chemistry

2011 ◽  
Vol 11 (2) ◽  
pp. 6845-6874
Author(s):  
S. X. Ma ◽  
J. D. Rindelaub ◽  
K. M. McAvey ◽  
P. D. Gagare ◽  
B. A. Nault ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Organic Aerosol ◽  
Reaction Chamber ◽  
Oxidation Products ◽  
Ozone Production ◽  
Organic Nitrate ◽  
Peroxy Radicals ◽  
Nitrate Precursor ◽  
Volatile Organic ◽  
Major Oxidation

Abstract. The biogenic volatile organic compound α-pinene is one of the dominant monoterpenes emitted to the Earth's atmosphere at an estimated rate of ~50 Tg yr−1. Its atmospheric oxidation products in the presence of NO can lead to ozone production, as well as production of secondary organic aerosol (SOA). The major oxidation pathway of α-pinene is reaction with OH, which in the presence of NO can form either α-pinene nitrates or convert NO to NO2, which can photolyze to form ozone. In this work, we successfully synthesized four α-pinene hydroxy nitrates through three different routes, and have identified the 4 individual isomers in α-pinene/OH/NO reaction chamber experiments. From the experiments, we determined their individual production yields, estimated the total RONO2 yield, and calculated the relative branching ratios of the nitrate precursor peroxy radicals (RO2). The combined yield of the four α-pinene nitrates was found to be 13.0 (±0.7) % at atmospheric pressure and 296 K, and the total organic nitrate yield was estimated to be 0.19 (+0.10/−0.06). We also determined the OH rate constants for two of the isomers, and have calculated their overall atmospheric lifetimes, which range between 22 and 38 h.

Chamber Studies of NO3 reactivity during the oxidation of isoprene

2020 ◽  
Author(s):  
Patrick Dewald ◽  
Justin Shenolikar ◽  
Nils Friedrich ◽  
Franz Rohrer ◽  
Ralf Tillmann ◽  
...  
Keyword(s):  
Oxidation Products ◽  
Research Centre ◽  
Biogenic Emissions ◽  
Organic Nitrates ◽  
Peroxy Radicals ◽  
Experimental Conditions ◽  
Mixing Ratios ◽  
Volatile Organic ◽  
Isoprene Oxidation ◽  
Chamber Studies

&lt;p&gt;Isoprene is the major volatile organic compound that is released into the environment via biogenic emissions and its oxidation can result in formation of secondary organic aerosol (SOA). Although isoprene emission occurs mainly at daytime, it can accumulate at nighttime and be oxidized by the nitrate radical (NO&lt;sub&gt;3&lt;/sub&gt;) to form organic nitrates that can partition to the particle phase. A detailed understanding of the reaction between isoprene and NO&lt;sub&gt;3&lt;/sub&gt; is thus required to predict its role in e.g. NO&lt;sub&gt;X&lt;/sub&gt; lifetimes and SOA formation.&lt;/p&gt;&lt;p&gt;The reaction between NO&lt;sub&gt;3&lt;/sub&gt; and isoprene was investigated under varying experimental conditions (high or low RO&lt;sub&gt;2&lt;/sub&gt;/HO&lt;sub&gt;2&lt;/sub&gt;, temperature, humidity, seed aerosols) during the NO3ISOP campaign at the atmospheric simulation chamber SAPHIR of the research centre in J&amp;#252;lich (Germany). Direct measurement of the NO&lt;sub&gt;3&lt;/sub&gt; reactivity was carried out with means of a flowtube coupled to a cavity-ring-down spectroscopy (FT-CRDS) setup which enabled the evolution of the NO&lt;sub&gt;3&lt;/sub&gt; lifetime during the isoprene oxidation process to be monitored.&lt;/p&gt;&lt;p&gt;By comparing direct NO&lt;sub&gt;3&lt;/sub&gt; reactivity measurements with those calculated from VOC mixing ratios and those calculated from a stationary-state analysis we identify the contributions of isoprene, secondary oxidation products and peroxy radicals to NO&lt;sub&gt;3&lt;/sub&gt; losses.&lt;/p&gt;

scholarly journals <i>α</i>-Pinene nitrates: synthesis, yields and atmospheric chemistry

2011 ◽  
Vol 11 (13) ◽  
pp. 6337-6347 ◽  
Author(s):  
S. X. Ma ◽  
J. D. Rindelaub ◽  
K. M. McAvey ◽  
P. D. Gagare ◽  
B. A. Nault ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Organic Aerosol ◽  
Reaction Chamber ◽  
Oxidation Products ◽  
Ozone Production ◽  
Organic Nitrate ◽  
Peroxy Radicals ◽  
Nitrate Precursor ◽  
Volatile Organic ◽  
Major Oxidation

Abstract. The biogenic volatile organic compound α-pinene is one of the dominant monoterpenes emitted to the Earth's atmosphere at an estimated rate of ~50 Tg C yr−1. Its atmospheric oxidation products in the presence of NO can lead to ozone production, as well as production of secondary organic aerosol (SOA). The major oxidation pathway of α-pinene is reaction with OH, which in the presence of NO can form either α-pinene nitrates or convert NO to NO2, which can photolyze to form ozone. In this work, we successfully synthesized four α-pinene hydroxy nitrates through three different routes, and have identified these 4 individual isomers in α-pinene/OH/NO reaction chamber experiments. From the experiments, we determined their individual production yields, estimated the total RONO2 yield, and calculated the relative branching ratios of the nitrate precursor peroxy radicals (RO2). The combined yield of the four α-pinene nitrates was found to be 0.130 (±0.035) at atmospheric pressure and 296 K, and the total organic nitrate yield was estimated to be 0.19 (+0.10/−0.06). We also determined the OH rate constants for two of the isomers, and have calculated their overall atmospheric lifetimes, which range between 22 and 38 h.

scholarly journals Isoprene nitrates: preparation, separation, identification, yields, and atmospheric chemistry

2010 ◽  
Vol 10 (4) ◽  
pp. 10625-10651 ◽  
Author(s):  
A. L. Lockwood ◽  
P. B. Shepson ◽  
M. N. Fiddler ◽  
M. Alaghmand
Keyword(s):  
Atmospheric Chemistry ◽  
Atmospheric Pressure ◽  
Oxidation Products ◽  
Ozone Production ◽  
Organic Nitrates ◽  
Relative Importance ◽  
Experimental Knowledge ◽  
Volatile Organic ◽  
Isoprene Nitrates ◽  
The Individual

Abstract. Isoprene is an important atmospheric volatile organic compound involved in ozone production and NOx (NO+NO2) sequestration and transport. Isoprene reaction with OH in the presence of NO can form either isoprene nitrates or convert NO to NO2 which can photolyze to form ozone. While it has been shown that isoprene nitrate production can represent an important sink for NOx in forest impacted environments, there is little experimental knowledge of the relative importance of the individual isoprene nitrate isomers, each of which has a different fate and reactivity. In this work, we have identified the 8 individual isomers and determined their total and individual production yields. The overall yield of isoprene nitrates at atmospheric pressure and 295 K was found to be 0.070(+0.025/–0.015). Three isomers, the (4,3)-IN, (1,2)-IN and Z-(4,1)-IN represent 90% of the total IN yield. We also determined the ozone rate constants for three of the isomers, and have calculated their atmospheric lifetimes, which range from ~1–2 h, making their oxidation products likely more important as atmospheric organic nitrates and sinks for nitrogen.

scholarly journals Isoprene nitrates: preparation, separation, identification, yields, and atmospheric chemistry

2010 ◽  
Vol 10 (13) ◽  
pp. 6169-6178 ◽  
Author(s):  
A. L. Lockwood ◽  
P. B. Shepson ◽  
M. N. Fiddler ◽  
M. Alaghmand
Keyword(s):  
Atmospheric Chemistry ◽  
Atmospheric Pressure ◽  
Oxidation Products ◽  
Ozone Production ◽  
Organic Nitrates ◽  
Relative Importance ◽  
Experimental Knowledge ◽  
Volatile Organic ◽  
Isoprene Nitrates ◽  
The Individual

Abstract. Isoprene is an important atmospheric volatile organic compound involved in ozone production and NOx (NO+NO2) sequestration and transport. Isoprene reaction with OH in the presence of NO can form either isoprene hydroxy nitrates ("isoprene nitrates") or convert NO to NO2 which can photolyze to form ozone. While it has been shown that isoprene nitrate production can represent an important sink for NOx in forest impacted environments, there is little experimental knowledge of the relative importance of the individual isoprene nitrate isomers, each of which has a different fate and reactivity. In this work, we have identified the 8 individual isomers and determined their total and individual production yields. The overall yield of isoprene nitrates at atmospheric pressure and 295 K was found to be 0.070(+0.025/−0.015). Three isomers, representing nitrates resulting from OH addition to a terminal carbon, represent 90% of the total IN yield. We also determined the ozone rate constants for three of the isomers, and have calculated their atmospheric lifetimes, which range from ~1–2 h, making their oxidation products likely more important as atmospheric organic nitrates and sinks for nitrogen.

Correlation between the sea level muon spectrum and the primary nucleon spectrum using the Cocconi–Koester–Perkins model

1979 ◽  
Vol 57 (7) ◽  
pp. 921-925 ◽  
Author(s):  
A. K. Chakrabarti ◽  
A. K. Das ◽  
A. K. De
Keyword(s):  
Sea Level ◽  
Pion Production ◽  
Spectral Shape ◽  
Muon Spectrum ◽  
Proton Proton ◽  
Absolute Value ◽  
Nucleon Spectrum ◽  
Scaling Models ◽  
The Mean ◽  
Good Agreement

Using the recent ISR data of proton–proton interactions on the inclusive production of pions and nucleons, realistic values of the mean pion inelasticity Kπ and the mean nucleon inelasticity KT have been estimated. These values have been used for the derivation of the sea level differential muon spectrum from the primary nucleon spectrum and vice versa using the CKP model as an extension of the work presented in an earlier article. It is found that none of the measured primary nucleon spectra of Ryan, Ormes, and Balasubrahmanyan and Grigorov, Rapoport, and Shestoperov fit any of the precisely measured muon spectra of Ayre, Baxendale, Hume, Nandi, Thompson, and Whalley and Allkofer, Carstensen, and Dau in spectral shape or the absolute value. On the other hand good agreement between the derived muon spectra and the spectra of Allkofer et al. and Ayre et al. is found if the primary nucleon spectra of the forms, N(Ep) = (1.38 ± 0.08)Ep−2.59 and N(Ep) = (1.00 ± 0.10)Ep−2.55, respectively, are assumed. The first form is comparable with that obtained by Brooke, Hayman, Kamiya, and Wolfendale following more approximate but similar procedure. It is also not unjustified when compared with the measured primary all nuclei spectrum of Grigorov et al. in the light of suggestions made by Ellsworth, Ito, Macfall, Siohan, Streitmatter, Tonwar, Vishwanath, Yodh, and Balasubrahmanyan. By comparing the pion production spectra derived from the same primary nucleon spectrum but using the CKP and the scaling models, it is concluded that the results are sensitive to the model assumed for the collisions.

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