RII Track-4 Biomass Burning Aerosols in the U.S. Southwest: Hygroscopic Properties from Emissions to Aging

野火是一个日益严重的全球性问题，在美国西部尤为紧迫。部分原因是美国持续升温和干旱，自2000年以来，与1960年至2000年的时间范围相比，美国被野火烧毁的平均面积增加了约2倍。除了与过去二十年极端事件有关的生命和财产的悲剧性损失外，野火趋势还促使人们越来越关注生物质烟雾对健康的影响。值得注意的是，高浓度的颗粒物（又称气溶胶）对人类健康的影响、大气能见度的影响和地球辐射收支尤其令人关切。烟雾气溶胶在大小、化学成分、形状和光学性质方面高度多样化。本研究在使用相关燃料的实验室燃烧实验以及烟雾气溶胶的环境测量中检查了这些特性。一个特别的焦点是这些粒子如何与大气相对湿度相互作用，从而改变这些光学特性。最后，这里测量的参数对于理解烟雾影响的大小和程度很重要；这些也是预测烟雾对空气质量和气候系统影响的计算机模型所需的关键输入。这项研究将为PI和学生的职业发展提供无与伦比的机会。生物质燃烧气溶胶日益降低全球空气质量，对气候影响的约束仍然很差。美国西南部缺乏对地方性和入侵物种的相关燃料的基本烟雾特性的详细测量。该项目通过对生物质燃烧排放的实验室实验来解决这些空白，重点是气溶胶吸水或吸湿性。研究的重点是生物质烟雾的实验室气溶胶测量。从发射到老化，探索气溶胶吸湿性、光学性质和化学成分之间的动态关系。本研究的具体目标是：(1)探索气溶胶吸湿性与燃料和土壤的联系；(2)利用腔衰减相移-单散射反照率（CAPS-SSA）方法改进测量气溶胶消光对湿度依赖性的新技术；(3)利用其他先进的气溶胶测量技术描述驱动烟雾气溶胶特性的框架。将采用一系列技术来提供对生物质烟雾微物理特性的独特见解。其中包括新墨西哥理工大学提供的几个项目（受控RH浊度计、多波长浊度计和光声消光计），这些项目将与洛斯阿拉莫斯国家实验室（LANL）的资源相结合。后者包括光声光谱法、粒径分布方法和先进的气溶胶技术，如气溶胶质谱法和光化学老化反应器。一项主要的合作任务是开发一种新的仪器，加湿CAPS-SSA。结合传统的湿度控制浊度测定法，这将允许探测光吸收和SSA的相对湿度依赖性。后者决定了气溶胶是造成净降温还是净升温的影响。本研究还包括植物和土壤的分析，以确定吸湿性的关键驱动因素。最终，这些结果使烟雾、燃料和土壤成分、燃烧特性和老化等关键气溶胶特性的预测框架得以发展。野火趋势以及美国西南地区不断变化的森林生态系统、水文联系和该地区稀缺的数据使其成为一个重要的主题。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical DescriptionWildland fire is an increasing global issue and particularly urgent in the western U.S. Due in part to continued increasing temperatures and drought in the nation, the average U.S. acreage burned in wildfires has increased by approximately a factor of 2 since the year 2000 in comparison with the time range of 1960-2000. Beyond tragic loss of life and property associated with extreme events of the past two decades, wildfire trends also prompt growing concerns with health impacts from biomass smoke. Notably, the high concentration of particulate matter, also known as aerosols is of particular concern for human health effects, atmospheric visibility impacts, and the planetary radiation budget. Smoke aerosols are highly diverse in terms of their size, chemical composition, shape and optical properties. This research examines these properties in laboratory combustion experiments using relevant fuels as well as ambient measurements of smoke aerosols. A particular focus is how these particles interact with atmospheric relative humidity, which changes these optical properties. In the end, parameters measured here are important to understanding the magnitude and extent of smoke impacts; these are also key inputs needed in computer models that predict smoke impacts on air quality and the climate system. The study under this fellowship will allow unparalleled opportunities for the career advancement of the PI and a student.Technical DescriptionBiomass burning aerosols increasingly degrade global air quality and remain poorly constrained with respect to climate effects. The Southwestern U.S. lacks detailed measurements of fundamental smoke properties for relevant fuels, for both endemic and invasive species. This project addresses these gaps with laboratory experiments on biomass burning emissions with a focus on aerosol water uptake, or hygroscopicity. The research focuses on laboratory aerosol measurements of biomass smoke?from emission to aging exploring the dynamics between aerosol hygroscopicity, optical properties, and chemical composition. Specific goals of this research are: (1) Explore the connection of aerosol hygroscopicity to fuels and soils, (2) Refine a new technique for measuring humidity dependence of aerosol light extinction using the Cavity Attenuated Phase Shift-Single Scattering Albedo (CAPS-SSA) method, (3) Use other advanced aerosol measurement techniques to describe a framework that drives smoke aerosol properties. An array of techniques will be employed to provide unique insights to biomass smoke microphysical properties. These include several contributed by New Mexico Tech (controlled RH nephelometry, multi-wavelength nephelometry, and a photoacoustic extinctiometer) that will be combined with resources at Los Alamos National Lab (LANL). The latter includes photoacoustic spectrometry, particle size distribution methods, and advanced aerosol techniques such as aerosol mass spectrometry and a photochemical aging reactor. A main collaborative task is the development of a new instrument, a humidified CAPS-SSA. In conjunction with traditional humidity controlled nephelometry, this will allow probing of the RH dependence of light absorption and SSA. The latter determines whether aerosols cause a net cooling or warming impact. This study also includes analysis of plants and soils to determine key drivers of hygroscopicity. Ultimately, the results enable development of a predictive framework of key aerosol properties from smoke, fuel, and soils composition, combustion properties and aging. Wildfire trends as well as the Southwest U.S. region's changing forest ecosystems, a hydrological connection, and scarce data in this region make this an important topic.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.