Evolution of Aerosols From Wood Smoke Influenced by Burning Phase and Solar Radiation

Emissions of carbonaceous aerosols (black carbon (BC) and organic aerosol (OA)) from biomass burning have important climate and human health impacts. Not only the primary emissions are complicated by combustion phases, but also the evolution after emission is not well understood. In this study, single plumes from residential wood burning, extracted from either flaming or smoldering phase, were injected into our novel chamber, to investigate their evolution in real atmospheric conditions with or without solar radiation. Initial compositions of flaming or smoldering plumes were dominated by BC or OA respectively. Replicable results showed that in light, smoldering plumes had faster secondary OA (SOA) formation than flaming. Furanic and carboxylic acid compounds were found to be the main gaseous precursors and products, respectively. Evaporation and photooxidation concurrently caused increased oxidation in the beginning, but at a later stage of evolution, SOA evolution showed remarkabledivergence: enhanced oxidation for smoldering but decreased for flaming plumes, leading to a higher oxygen-to-carbon ratio for smoldering than flaming up to 0.25. OA from flaming conditions showed a higher absorptivity than from smoldering conditions, as OA is mostly internally and externally mixed with BC, respectively. For flaming (smoldering), the imaginary refractive index of OA (k_OA) was initially at 0.03 ± 0.01 (0.001) and 0.15 ± 0.02 (0.05 ± 0.02) at λ = 781 and 405 nm, respectively, with a half-decay time of 2−3 h in light but a <40% decrease under dark within 5 h. The production of less-absorbing SOA in the first 1−2 h and possible subsequent photobleaching of chromophores contributed to the decrease of k_OA. The enhanced abundance but decreased absorptivity of coatings on BC resulted in a relatively maintainable absorptivity of BC-containing particles during evolution. Distinct particulate/gas emissions and resultant evolutions at different combustion phases should be therefore considered in evaluating the impacts of biomass burning emissions.

Dantong Liu*, Siyuan Li, Dawei Hu, Shaofei Kong*, Yi Cheng, Yangzhou Wu, Shuo Ding, Kang Hu, Shurui Zheng, Qin Yan, Huang Zheng, Delong Zhao, Ping Tian, Jianhuai Ye, Mengyu Huang, Deping Ding: Evolution of Aerosol Optical Properties from Wood Smoke in Real Atmosphere Influenced by Burning Phase and Solar Radiation, Environmental Science & Technology, 55(9), 5677–5688, 10.1021/acs.est.0c07569, 2021.

Siyuan Li, Dantong Liu*, Dawei Hu, Shaofei Kong, Yangzhou Wu, Shuo Ding, Yi Cheng, Hao Qiu, Shurui Zheng, Qin Yan, Huang Zheng, Kang Hu, Jiale Zhang, Delong Zhao, Quan Liu, Jiujiang Sheng, Jianhuai Ye, Hui He, Deping Ding: Evolution of organic aerosol from wood smoke influenced by burning phase and solar radiation, Journal of Geophysical Research – Atmospheres, 126(8), 10.1029/2021JD034534, 2021.