Inorganic salts are a significant component of biomass-burning aerosol (BBA) and have inconsistently been observed to undergo chemical reactions with strong acids and other reactants during atmospheric aging, altering particle hygroscopicity and further reactivity while also liberating reactive halides such as ClNO₂(g) and HCl(g) and recycling or removing nitrogen oxides. The condensation of organic carbon to BBA coemitted by wildfires and other biomass combustion processes can affect aerosol particle reactivity with trace gases. These organic coatings along with deliquescence of chloride salts requiring high relative humidities >80% were recently proposed to explain the low observed reaction probability of N₂O₅(g) with BBA. We performed a series of single-particle analyses to characterize the morphology and composition of laboratory-generated BBA from authentic fuels using transmission and scanning electron microscopies (T/SEM) to test this hypothesis. Stable organic coatings that appear thicker or more oxidized than the particle bulk (likely tar balls) were observed to form on some spherical BBA particles but only when photooxidation was not applied. Inorganic salt components were inconsistently observed to react during simulated photooxidative atmospheric aging, sometimes undergoing chloride displacement reactions with strong acid vapors to produce sulfate and nitrate salts. Particles were also observed where chloride-salt regions were not completely depleted by reaction with strong acids. Organic carbon particle coatings plus the physical phase of chloride salts and deliquescence limitations appear to play a significant role in determining in which particles and fuel types these chloride displacement reactions can occur and the extent of these reactions with acidic vapors.

中文翻译：

---

生物质燃烧颗粒上有机碳涂层的形态及其在反应气体吸收中的作用

无机盐是生物质燃烧气溶胶 (BBA) 的重要组成部分，并且在大气老化过程中与强酸和其他反应物发生化学反应，改变粒子吸湿性和进一步反应性，同时还释放出反应性卤化物，如 ClNO ₂ (g ) 和 HCl(g) 并回收或去除氮氧化物。野火和其他生物质燃烧过程共同产生的有机碳凝结成 BBA 会影响气溶胶颗粒与微量气体的反应性。最近提出这些有机涂层以及需要 >80% 的高相对湿度的氯化物盐的潮解来解释观察到的 N ₂ O ₅的低反应概率(g) 与 BBA。我们进行了一系列单粒子分析，以使用透射和扫描电子显微镜 (T/SEM) 来表征实验室生成的来自真实燃料的 BBA 的形态和成分，以测试这一假设。观察到在一些球形 BBA 颗粒上形成了比颗粒体（可能是焦油球）更厚或更氧化的稳定有机涂层，但仅当未应用光氧化时。在模拟光氧化大气老化过程中观察到无机盐成分的反应不一致，有时会与强酸蒸汽发生氯化物置换反应以产生硫酸盐和硝酸盐。在氯化物-盐区域未通过与强酸反应完全耗尽的地方也观察到颗粒。