Abstract
In tropospheric chemistry, secondary organic aerosol (SOA) is deemed an end product. Here, on the basis of new evidence, we make the case that SOA is a key reactive intermediate. We present laboratory results on the catalysis by carboxylate anions of the disproportionation of NO2 'on water': 2NO2 + H2O = HONO + NO3- + H + (R1), and supporting quantum chemical calculations, which we apply to reinterpret recent reports on (i) HONO daytime source strengths vis-à-vis SOA anion loadings and (ii) the weak seasonal and latitudinal dependences of NOx decay kinetics over several megacities. HONO daytime generation via R1 should track sunlight because it is generally catalyzed by the anions produced during the photochemical oxidation of pervasive gaseous pollutants. Furthermore, by proceeding on the everpresent substrate of aquated airborne particulates, R1 can eventually overtake the photolysis of NO2: NO2 + hν = NO + O(3P) (R2), at large zenith angles. Thus, since R1 leads directly to OH-radical generation via HONO photolysis: HONO + hν = NO + OH, whereas the path initiated by R2 is more circuitous and actually controlled by the slower photolysis of O3: O3 + hν (+H2O) = O2 + 2OH, the competition between R1 and R2 provides a mechanistic switch that buffers OH concentrations and NO2 decay (via R1 and/or NO2 + OH = HNO3) from actinic flux variations.
| Original language | English |
|---|---|
| Pages (from-to) | 407-420 |
| Number of pages | 14 |
| Journal | Faraday Discussions |
| Volume | 165 |
| DOIs | |
| Publication status | Published - Oct 18 2013 |
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All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
Cite this
Tropospheric aerosol as a reactive intermediate. / Colussi, Agustín J.; Enami, Shinichi; Yabushita, Akihiro; Hoffmann, Michael R.; Liu, Wei Guang; Mishra, Himanshu; Goddard, William A.
In: Faraday Discussions, Vol. 165, 18.10.2013, p. 407-420.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Tropospheric aerosol as a reactive intermediate
AU - Colussi, Agustín J.
AU - Enami, Shinichi
AU - Yabushita, Akihiro
AU - Hoffmann, Michael R.
AU - Liu, Wei Guang
AU - Mishra, Himanshu
AU - Goddard, William A.
PY - 2013/10/18
Y1 - 2013/10/18
N2 - In tropospheric chemistry, secondary organic aerosol (SOA) is deemed an end product. Here, on the basis of new evidence, we make the case that SOA is a key reactive intermediate. We present laboratory results on the catalysis by carboxylate anions of the disproportionation of NO2 'on water': 2NO2 + H2O = HONO + NO3- + H + (R1), and supporting quantum chemical calculations, which we apply to reinterpret recent reports on (i) HONO daytime source strengths vis-à-vis SOA anion loadings and (ii) the weak seasonal and latitudinal dependences of NOx decay kinetics over several megacities. HONO daytime generation via R1 should track sunlight because it is generally catalyzed by the anions produced during the photochemical oxidation of pervasive gaseous pollutants. Furthermore, by proceeding on the everpresent substrate of aquated airborne particulates, R1 can eventually overtake the photolysis of NO2: NO2 + hν = NO + O(3P) (R2), at large zenith angles. Thus, since R1 leads directly to OH-radical generation via HONO photolysis: HONO + hν = NO + OH, whereas the path initiated by R2 is more circuitous and actually controlled by the slower photolysis of O3: O3 + hν (+H2O) = O2 + 2OH, the competition between R1 and R2 provides a mechanistic switch that buffers OH concentrations and NO2 decay (via R1 and/or NO2 + OH = HNO3) from actinic flux variations.
AB - In tropospheric chemistry, secondary organic aerosol (SOA) is deemed an end product. Here, on the basis of new evidence, we make the case that SOA is a key reactive intermediate. We present laboratory results on the catalysis by carboxylate anions of the disproportionation of NO2 'on water': 2NO2 + H2O = HONO + NO3- + H + (R1), and supporting quantum chemical calculations, which we apply to reinterpret recent reports on (i) HONO daytime source strengths vis-à-vis SOA anion loadings and (ii) the weak seasonal and latitudinal dependences of NOx decay kinetics over several megacities. HONO daytime generation via R1 should track sunlight because it is generally catalyzed by the anions produced during the photochemical oxidation of pervasive gaseous pollutants. Furthermore, by proceeding on the everpresent substrate of aquated airborne particulates, R1 can eventually overtake the photolysis of NO2: NO2 + hν = NO + O(3P) (R2), at large zenith angles. Thus, since R1 leads directly to OH-radical generation via HONO photolysis: HONO + hν = NO + OH, whereas the path initiated by R2 is more circuitous and actually controlled by the slower photolysis of O3: O3 + hν (+H2O) = O2 + 2OH, the competition between R1 and R2 provides a mechanistic switch that buffers OH concentrations and NO2 decay (via R1 and/or NO2 + OH = HNO3) from actinic flux variations.
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U2 - 10.1039/c3fd00040k
DO - 10.1039/c3fd00040k
M3 - Article
VL - 165
SP - 407
EP - 420
JO - Faraday Discussions
JF - Faraday Discussions
SN - 1364-5498
ER -