Department of Atmospheric Science , Colorado State University , Fort Collins , Colorado 80523 , United States.
Department of Mechanical Engineering , Colorado State University , Fort Collins , Colorado 80523 , United States.
Environ Sci Technol. 2019 Sep 3;53(17):10007-10022. doi: 10.1021/acs.est.9b02588. Epub 2019 Aug 12.
Biomass burning is a major source of atmospheric particulate matter (PM) with impacts on health, climate, and air quality. The particles and vapors within biomass burning plumes undergo chemical and physical aging as they are transported downwind. Field measurements of the evolution of PM with plume age range from net decreases to net increases, with most showing little to no change. In contrast, laboratory studies tend to show significant mass increases on average. On the other hand, similar effects of aging on the average PM composition (e.g., oxygen-to-carbon ratio) are reported for lab and field studies. Currently, there is no consensus on the mechanisms that lead to these observed similarities and differences. This review summarizes available observations of aging-related biomass burning aerosol mass concentrations and composition markers, and discusses four broad hypotheses to explain variability within and between field and laboratory campaigns: (1) variability in emissions and chemistry, (2) differences in dilution/entrainment, (3) losses in chambers and lines, and (4) differences in the timing of the initial measurement, the baseline from which changes are estimated. We conclude with a concise set of research needs for advancing our understanding of the aging of biomass burning aerosol.
生物质燃烧是大气颗粒物（PM）的主要来源，对健康、气候和空气质量都有影响。在顺风输送过程中，生物质燃烧羽流中的颗粒和蒸气会经历化学和物理老化。对 PM 随羽流年龄演变的现场测量结果从净减少到净增加不等，大多数结果显示变化很小或没有变化。相比之下，实验室研究往往平均显示出显著的质量增加。另一方面，实验室和现场研究都报告了老化对平均 PM 组成（例如，氧碳比）的相似影响。目前，对于导致这些观察到的相似性和差异性的机制尚未达成共识。本综述总结了与老化相关的生物质燃烧气溶胶质量浓度和组成标志物的现有观测结果，并讨论了四个广泛的假设，以解释现场和实验室实验之间以及内部的可变性：（1）排放和化学变化的可变性，（2）稀释/夹带的差异，（3）腔室和管路中的损耗，以及（4）初始测量的时间差异，即估计变化所依据的基线。最后，我们提出了一组简明的研究需求，以推进我们对生物质燃烧气溶胶老化的认识。
