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Secondary Organic Aerosol (SOA) from Photo-Oxidation of Toluene: 1 Influence of Reactive Nitrogen, Acidity and Water Vapours on Optical Properties
| Content Provider | MDPI |
|---|---|
| Author | Mitra, Kalyan Mishra, Harsh Raj Pei, Xiangyu Pathak, Ravi Kant |
| Copyright Year | 2022 |
| Description | Many climate models treat the light-absorbing SOA component called “brown carbon” (BrC) as non-light absorbing because its formation and transformations are poorly understood. We therefore investigated the influence of reactive nitrogen $(NO_{x}$, $NH_{3}$)-, acidity $(H_{2}SO_{4}$)-, and water-mediated chemistry on SOA formed by the photo-oxidation of toluene, the subsequent formation and transformation of BrC, and its optical properties. We discovered that nitrogen-poor (NP) SOA is formed when the molar ratio of $NO_{x}$ to reacted toluene (henceforth, $[NO_{x}$/ΔHC]) is 0.15 or less, whereas nitrogen-rich (NR) SOA is formed when $[NO_{x}$/ΔHC] > 0.15. NR and NP SOA have markedly different characteristics. The light absorption coefficient $(B_{abs}$) and mass absorption cross-section (MAC) of the SOA increased with $[NO_{x}$/ΔHC] under both the NP and NR regimes. For NP SOA, the MAC increased with $[NO_{x}$/ΔHC] independently of the relative humidity (RH). However, the MAC of NR SOA was RH-dependent. Under both NP and NR regimes, acidity promoted SOA browning while $NH_{3}$ increased $B_{abs}$ and MAC at 80% RH. The highest MAC was observed at the lowest RH (20%) for acidic NR SOA, and it was postulated that the MAC of SOA depends mainly on the pH and the [H^{+}$]_{free}$/[SOA mass] ratio of the aqueous SOA phase. |
| Starting Page | 1099 |
| e-ISSN | 20734433 |
| DOI | 10.3390/atmos13071099 |
| Journal | Atmosphere |
| Issue Number | 7 |
| Volume Number | 13 |
| Language | English |
| Publisher | MDPI |
| Publisher Date | 2022-07-13 |
| Access Restriction | Open |
| Subject Keyword | Atmosphere Environmental Sciences Switching Optical Property Photo-oxidation Secondary Organic Aerosol (soa) Nox Ramping Nitrogen-poor (np) Nitrogen-rich (nr) Toluene Sulfuric Acid Ammonia Ramping |
| Content Type | Text |
| Resource Type | Article |
