Characterization of organic aerosols from a Chinese megacity during winter: predominance of fossil fuel combustion
oleh: Md. M. Haque, Md. M. Haque, Md. M. Haque, K. Kawamura, D. K. Deshmukh, C. Fang, C. Fang, W. Song, W. Song, B. Mengying, B. Mengying, Y.-L. Zhang, Y.-L. Zhang
| Format: | Article |
|---|---|
| Diterbitkan: | Copernicus Publications 2019-04-01 |
Deskripsi
<p>PM<span class="inline-formula"><sub>2.5</sub></span> aerosol samples were collected from the Chinese megacity of Nanjing (32.21<span class="inline-formula"><sup>∘</sup></span> N, 118.73<span class="inline-formula"><sup>∘</sup></span> E) during winter and analyzed for a total of 127 compounds from 12 organic compound classes. The most abundant classes of compounds were <span class="inline-formula"><i>n</i></span>-alkanes (mean concentration of 205 ng m<span class="inline-formula"><sup>−3</sup></span>), followed by fatty acids (76.3 ng m<span class="inline-formula"><sup>−3</sup></span>), polycyclic aromatic hydrocarbons (PAHs; 64.3 ng m<span class="inline-formula"><sup>−3</sup></span>), anhydrosugars (56.3 ng m<span class="inline-formula"><sup>−3</sup></span>), fatty alcohols (40.5 ng m<span class="inline-formula"><sup>−3</sup></span>) and phthalate esters (15.2 ng m<span class="inline-formula"><sup>−3</sup></span>), whereas hydroxy-/polyacids (8.33 ng m<span class="inline-formula"><sup>−3</sup></span>), aromatic acids (7.35 ng m<span class="inline-formula"><sup>−3</sup></span>), hopanes (4.19 ng m<span class="inline-formula"><sup>−3</sup></span>), primary sugars and sugar alcohols (4.15 ng m<span class="inline-formula"><sup>−3</sup></span>), lignin and resin products (2.94 ng m<span class="inline-formula"><sup>−3</sup></span>), and steranes (2.46 ng m<span class="inline-formula"><sup>−3</sup></span>) were less abundant. The carbon preference index of <span class="inline-formula"><i>n</i></span>-alkanes (0.83–1.38) indicated that they had a strong fossil fuel combustion origin. Diagnostic concentration ratios of organic tracers suggested that PAHs and hopanes originated mostly from coal burning and traffic emissions, respectively, in the Nanjing urban area. Positive matrix factorization analysis demonstrated that fossil fuel combustion was the major pollution source (28.7 %), followed by emissions from biomass burning (17.1 %), soil dust (14.5 %) and plastic burning (6.83 %) for Nanjing winter aerosols, although the contribution of secondary oxidation products (32.9 %) was the most abundant. Most of the compounds generally showed higher concentrations at nighttime compared with daytime; this was due to the accumulation process associated with inversion layers and the enhancement of emissions from heavy trucks at night. We conclude that fossil fuel combustion largely influences the winter organic aerosols in urban Nanjing. Based on the comparison of this study's results with previous research, we found that pollution levels in organic aerosols have decreased in the urban Nanjing atmosphere over the last decade.</p>