Department of Chemistry, University of British Columbia, Vancouver, V6T 1Z1 BC, Canada.
College of Environmental Science and Engineering, Tongji University, Shanghai 200072, China.
Environ Sci Technol. 2024 Oct 15;58(41):18284-18294. doi: 10.1021/acs.est.4c05650. Epub 2024 Oct 4.
Biomass burning organic aerosol (BBOA), containing brown carbon chromophores, plays a critical role in atmospheric chemistry and climate forcing. However, the effects of evaporation on BBOA volatility and viscosity under different environmental conditions remain poorly understood. This study focuses on the molecular characterization of laboratory-generated BBOA proxies from wood pyrolysis emissions. The initial mixture, "pyrolysis oil (PO)", was progressively evaporated to produce more concentrated mixtures (PO, PO, and PO) with volume reduction factors of 1.33, 2, and 3, respectively. Chemical speciation and volatility were investigated using temperature-programmed desorption combined with direct analysis in real-time ionization and high-resolution mass spectrometry (TPD-DART-HRMS). This novel approach quantified saturation vapor pressures and enthalpies of individual species, enabling the construction of volatility basis set distributions and the quantification of gas-particle partitioning. Viscosity estimates, validated by poke-flow experiments, showed a significant increase with evaporation, slowing particle-phase diffusion and extending equilibration times. These findings suggest that highly viscous tar ball particles in aged biomass burning emissions form as semivolatile components evaporate. The study highlights the importance of evaporation processes in shaping BBOA properties, underscoring the need to incorporate these factors into atmospheric models for better predictions of BBOA aging and its environmental impact.
生物质燃烧有机气溶胶（BBOA）含有棕色碳发色团，在大气化学和气候强迫中起着关键作用。然而，在不同环境条件下蒸发对 BBOA 挥发性和粘度的影响仍了解甚少。本研究专注于木质热解排放物生成的实验室 BBOA 示踪剂的分子特征。初始混合物“热解油（PO）”逐渐蒸发，产生更浓缩的混合物（PO、PO 和 PO），体积缩减因子分别为 1.33、2 和 3。采用程序升温解吸结合实时直接分析电离和高分辨率质谱（TPD-DART-HRMS）研究了化学形态和挥发性。这种新方法定量了各物种的饱和蒸气压和焓，从而构建了挥发性基组分布，并定量了气粒分配。通过 poke-flow 实验验证的粘度估算值显示随着蒸发显著增加，从而减缓了颗粒相扩散并延长了平衡时间。这些发现表明，在老化的生物质燃烧排放物中，高度粘性的焦油球颗粒是作为半挥发性成分蒸发形成的。该研究强调了蒸发过程对 BBOA 性质的塑造作用，突出了需要将这些因素纳入大气模型中，以更好地预测 BBOA 的老化及其环境影响。
