Examination of brown carbon absorption from wildfires in the western US during the WE-CAN study
Examination of brown carbon absorption from wildfires in the western US during the WE-CAN study
复制标题
DOI：
10.5194/acp-22-13389-2022
复制
发表时间：
2022-10
影响因子：
6.3
通讯作者：
A. Sullivan;R. Pokhrel;Yingjie Shen;S. Murphy;D. Toohey;T. Campos;J. Lindaas;E. Fischer;Jeffrey L. Collett Jr.
中科院分区：
文献类型：
--
作者：
A. Sullivan;R. Pokhrel;Yingjie Shen;S. Murphy;D. Toohey;T. Campos;J. Lindaas;E. Fischer;Jeffrey L. Collett Jr.
抽象的。光吸收有机碳或棕色碳（BrC）可以是可见光吸收预算的重要贡献者。然而，BrC的来源和BrC对光吸收的贡献还不清楚。生物质燃烧被认为是溴化碳的主要来源。因此，作为WE-CAN（云化学，气溶胶吸收和氮的西部野火实验）研究的一部分，BrC吸收数据是在美国国家科学基金会/国家大气研究中心（NSF/NCAR）C-130飞机上收集的，因为它在2018年7月至8月拦截了美国西部野火的烟雾。BrC吸收测量获得近实时使用两种技术。第一个将颗粒进液采样器（PILS）与液体波导毛细管池和总有机碳分析仪耦合，用于测量水溶性BrC吸收和WSOC（水溶性有机碳）。第二个采用定制的光声气溶胶吸收光谱仪（PAS），以测量在405和660 nm的总吸收。通过假设PAS在660 nm处测定的吸收等同于炭黑（BC）吸收，并且BC气溶胶吸收λ ngström指数为1，计算405 nm处的PAS BrC吸收（PAS总Abs 405 BrC）。从PILS和PAS的数据相结合，以研究在WE-CAN期间采样的各种野火羽流中在405 nm处的水溶性与总BrC吸收。WSOC、PILS水溶性Abs 405和PAS总Abs 405在烟羽流中和烟羽流外相互追踪。BrC吸收与WSOC（PAS的R2值=0.42和PILS =0.60）和CO（一氧化碳）（PAS的R2值=0.76和PILS =0.55）的所有野火采样。使用计算的UHSAS（超高灵敏度气溶胶光谱仪）气溶胶质量，针对气溶胶的非水溶性部分校正PILS水溶性Abs 405。经校正的PILS水溶性Abs 405与PAS总Abs 405 BrC显示出良好的闭合性，差异因子为1.5至2。分别通过PAS与PILS测量的颗粒与本体溶液吸收解释了这种差异，并通过Mie理论计算证实。在WE-CAN期间，观察到约45%（范围为31%至65%）的BrC吸收是由于水溶性物质。BrC吸收与WSOC或ΔCO的比值与火动力学或自排放后9 h内的时间没有明显的依赖关系。
Abstract. Light absorbing organic carbon, or brown carbon (BrC), can be a significant contributor to the visible light absorption budget. However, the sources of BrC and the contributions of BrC to light absorption are not well understood. Biomass burning is thought to be a major source of BrC. Therefore, as part of the WE-CAN (Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption and Nitrogen) study, BrC absorption data were collected on board the National Science Foundation/National Center for Atmospheric Research (NSF/NCAR) C-130 aircraft as it intercepted smoke from wildfires in the western US in July–August 2018. BrC absorption measurements were obtained in near real-time using two techniques. The first coupled a particle-into-liquid sampler (PILS) with a liquid waveguide capillary cell and a total organic carbon analyzer for measurements of water-soluble BrC absorption and WSOC (water-soluble organic carbon). The second employed a custom-built photoacoustic aerosol absorption spectrometer (PAS) to measure total absorption at 405 and 660 nm. The PAS BrC absorption at 405 nm (PAS total Abs 405 BrC) was calculated by assuming the absorption determined by the PAS at 660 nm was equivalent to the black carbon (BC) absorption and the BC aerosol absorption Ångström exponent was 1. Data from the PILS and PAS were combined to investigate the water-soluble vs. total BrC absorption at 405 nm in the various wildfire plumes sampled during WE-CAN. WSOC, PILS water-soluble Abs 405, and PAS total Abs 405 tracked each other in and out of the smoke plumes. BrC absorption was correlated with WSOC (R2 value for PAS =0.42 and PILS =0.60) and CO (carbon monoxide) (R2 value for PAS =0.76 and PILS =0.55) for all wildfires sampled. The PILS water-soluble Abs 405 was corrected for the non-water-soluble fraction of the aerosol using the calculated UHSAS (ultra-high-sensitivity aerosol spectrometer) aerosol mass. The corrected PILS water-soluble Abs 405 showed good closure with the PAS total Abs 405 BrC with a factor of ∼1.5 to 2 difference. This difference was explained by particle vs. bulk solution absorption measured by the PAS vs. PILS, respectively, and confirmed by Mie theory calculations. During WE-CAN, ∼ 45 % (ranging from 31 % to 65 %) of the BrC absorption was observed to be due to water-soluble species. The ratio of BrC absorption to WSOC or ΔCO showed no clear dependence on fire dynamics or the time since emission over 9 h.