Optical properties of biomass burning aerosol during the 2021 Oregon fire season: comparison between wild and prescribed fires
Optical properties of biomass burning aerosol during the 2021 Oregon fire season: comparison between wild and prescribed fires
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DOI：
10.1039/d2ea00118g
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发表时间：
2023-02-15
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影响因子：
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通讯作者：
Fry, Juliane L.
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作者：
Marsavin, Andrey;van Gageldonk, Ralph;Fry, Juliane L.
2021 年是俄勒冈州的极端森林火灾年，学士山天文台（MBO，距地面 2.76 公里）经常受到生物质燃烧 (BB) 烟雾的影响。我们使用细颗粒物 (PM1) 和干燥气溶胶散射和吸收系数（sigma(scat) 和 sigma(abs)）的测量来确定 2021 年 4 月至 9 月在 MBO 观测到的 27 个 BB 事件的强气溶胶光学特性。在研究期间还测量了一氧化碳 (CO)、二氧化碳 (CO2) 和总氧化氮 (NOy)。 4 月至 5 月期间，有 4 起 BB 事件源自规定火灾 (PF)，6 月至 9 月期间，有 23 起事件源自野火 (WF)。平均而言，PF 事件的 Delta PM1/Delta CO 标准化增强比 (NER) 较高，我们认为这是由于在较冷的环境温度下羽流快速稀释过程中有机气溶胶凝结效率更高。同时，PF 事件在 652 nm 处表现出显着较高的 Delta sigma(abs)/Delta CONER，表明黑碳成分较大。我们将此归因于更高效的燃烧，并得到更高的改进燃烧效率 (MCE) 以及 PF 事件中更高的 Delta NOy/Delta CONER 的支持。所有生物质燃烧事件的中值质量散射效率（MSE；sigma(scat)/PM1）范围为 3.3 至 7.4 m(2) g(-1)（530 nm），WF 和 PF 事件之间没有显着差异。我们发现 MSE 与羽流浓度 (Delta PM1) 呈正相关，与散射埃指数呈负相关，这表明浓烟中的快速凝结驱动尺寸分布朝向具有更高散射效率的较大颗粒。
The Mt. Bachelor Observatory (MBO, 2.76 km a.s.l.) was frequently impacted by biomass burning (BB) smoke in 2021, an extreme forest fire year in the state of Oregon. We used measurements of fine particulate matter (PM1) and dry aerosol scattering and absorption coefficients (sigma(scat) and sigma(abs)) to determine intensive aerosol optical properties for 27 BB events observed at MBO from April to September 2021. Measurements of carbon monoxide (CO), carbon dioxide (CO2), and total oxidized nitrogen (NOy) were also made during the study period. Four BB events originated from prescribed fires (PFs) between April and May, and 23 events originated from wildfires (WFs) between June and September. On average, the Delta PM1/Delta CO normalized enhancement ratio (NER) was higher for the PF events, which we propose is due to more efficient organic aerosol condensation during quick plume dilution at colder ambient temperatures. At the same time, the PF events exhibited significantly higher Delta sigma(abs)/Delta CO NERs at 652 nm, indicating a larger black carbon component. We attribute this to more efficient combustion, as supported by higher modified combustion efficiency (MCE) as well as higher Delta NOy/Delta CO NERs for the PF events. Median mass scattering efficiencies (MSE; sigma(scat)/PM1) ranged from 3.3 to 7.4 m(2) g(-1) (at 530 nm) across all biomass burning events, with no significant difference between WF and PF events. We found MSE to be positively correlated with plume concentration (Delta PM1) and negatively correlated with the scattering angstrom ngstrom exponent, suggesting that fast coagulation in dense smoke drives size distributions towards larger particles with greater scattering efficiency.