Zhang Jun, Zuend Andreas, Top Jens, Surdu Mihnea, Ei Haddad Imad, Slowik Jay G, Prevot Andre S H, Bell David M
PSI Center for Energy and Environmental Sciences, Paul Scherrer Institute (PSI), 5232 Villigen, Switzerland.
Department of Atmospheric and Oceanic Sciences, McGill University, Montréal, Quebec H3A 0B9, Canada.
Environ Sci Technol Lett. 2024 Nov 3;11(11):1214-1219. doi: 10.1021/acs.estlett.4c00608. eCollection 2024 Nov 12.
Biomass burning (BB) is a major source of aerosols and black carbon, thereby exerting an important impact on climate and air quality. Levoglucosan is the most well-recognized organic marker compound of BB and has been used to quantitatively assess BB's contribution to ambient aerosols. However, little is known about levoglucosan's evaporation under atmospheric conditions, primarily due to the uncertainty of its effective saturation vapor concentration () and its unknown activity coefficient (γ), in the complex BB emission matrix. Here, we utilized a thermodenuder to investigate the evaporation of levoglucosan from mixtures with polyethylene glycol (PEG) or BB primary organic aerosol (BBPOA) matrices, respectively. We estimate a pure component log(/[μg m]) of levoglucosan of 1.1 ± 0.1 at 298 K. We reveal that levoglucosan mixed with PEG or BBPOA becomes more volatile than when treated as a single component due to nonideal molecular interactions. Considering that phase separation might occur in such systems, we term γ apparent activity coefficient (γ ). We estimate log * and γ of levoglucosan in BBPOA of 1.8 ± 0.1 and 3.8 ± 0.3, assuming a liquid phase state. Consequently, γ must be considered to avoid significant underestimation of levoglucosan evaporation via gas-particle partitioning during transport.
生物质燃烧（BB）是气溶胶和黑碳的主要来源，因此对气候和空气质量产生重要影响。左旋葡聚糖是最广为人知的生物质燃烧有机标志物化合物，已被用于定量评估生物质燃烧对环境气溶胶的贡献。然而，对于左旋葡聚糖在大气条件下的蒸发情况知之甚少，这主要是由于在复杂的生物质燃烧排放矩阵中，其有效饱和蒸汽浓度（）存在不确定性，且其活度系数（γ）未知。在此，我们利用热脱附器分别研究了左旋葡聚糖在与聚乙二醇（PEG）或生物质燃烧一次有机气溶胶（BBPOA）基质的混合物中的蒸发情况。我们估计在298 K时，左旋葡聚糖的纯组分log（/[μg m]）为1.1±0.1。我们发现，由于非理想分子相互作用，与PEG或BBPOA混合的左旋葡聚糖比单独作为一种组分时更易挥发。考虑到此类系统中可能会发生相分离，我们将γ称为表观活度系数（γ ）。假设为液相状态，我们估计BBPOA中左旋葡聚糖的log *和γ 分别为1.8±0.1和3.8±0.3。因此，必须考虑γ ，以避免在传输过程中通过气粒分配对左旋葡聚糖蒸发的显著低估。
