ABSTRACT Absorptivity measurements with a laser-heating approach, referred to as the laser-driven thermal reactor (LDTR), were carried out in the infrared and applied at ambient (laboratory) nonreacting conditions to particle-laden filters from a three-wavelength (visible) particle/soot absorption photometer (PSAP). The particles were obtained during the Biomass Burning Observation Project (BBOP) field campaign. The focus of this study was to determine the particle absorption coefficient from field-campaign filter samples using the LDTR approach, and compare results with other commercially available instrumentation (in this case with the PSAP, which has been compared with numerous other optical techniques). Advantages of the LDTR approach include (1) direct estimation of material absorption from temperature measurements (as opposed to resolving the difference between the measured reflection/scattering and transmission), (2) information on the filter optical properties, and (3) identification of the filter material effects on particle absorption (e.g., leading to particle absorption enhancement or shadowing). For measurements carried out under ambient conditions, the particle absorptivity is obtained with a thermocouple placed flush with the filter back surface and the laser probe beam impinging normal to the filter particle-laden surface. Thus, in principle one can employ a simple experimental arrangement to measure simultaneously both the transmissivity and absorptivity (at different discrete wavelengths) and ascertain the particle absorption coefficient. For this investigation, LDTR measurements were carried out with PSAP filters (pairs with both blank and exposed filters) from eight different days during the campaign, having relatively light but different particle loadings. The observed particles coating the filters were found to be carbonaceous (having broadband absorption characteristics). The LDTR absorption coefficient compared well with results from the PSAP. The analysis was also expanded to account for the filter fiber scattering on particle absorption in assessing particle absorption enhancement and shadowing effects. The results indicated that absorption enhancement effects were significant, and diminished with increased filter particle loading.

中文翻译：

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来自生物质燃烧观测项目 (BBOP) 现场活动的 PSAP 颗粒过滤器的吸收/传输测量

摘要 使用激光加热方法（称为激光驱动热反应器 (LDTR)）的吸收率测量在红外线中进行，并在环境（实验室）非反应条件下应用于三波长（可见光）的颗粒负载过滤器。 ) 颗粒/碳烟吸收光度计 (PSAP)。这些颗粒是在生物质燃烧观测项目 (BBOP) 野外活动期间获得的。本研究的重点是使用 LDTR 方法确定现场运动过滤器样品的颗粒吸收系数，并将结果与​​其他市售仪器（在本例中为 PSAP，已与许多其他光学技术进行了比较）进行比较。LDTR 方法的优点包括 (1) 从温度测量中直接估计材料吸收（与解决测量的反射/散射和透射之间的差异相反），(2) 有关滤波器光学特性的信息，以及 (3) 识别过滤材料对粒子吸收的影响（例如，导致粒子吸收增强或阴影）。对于在环境条件下进行的测量，颗粒吸收率是通过将热电偶放置在与过滤器背面齐平的位置，并且激光探测光束垂直于过滤器颗粒负载表面来获得的。因此，原则上，可以采用一种简单的实验装置同时测量透射率和吸收率（在不同的离散波长下）并确定粒子吸收系数。在这项调查中，LDTR 测量是使用 PSAP 过滤器（与空白过滤器和暴露过滤器配对）在活动期间的八天进行的，具有相对较轻但不同的颗粒负载。观察到的覆盖过滤器的颗粒被发现是含碳的（具有宽带吸收特性）。LDTR 吸收系数与来自 PSAP 的结果相比很好。在评估粒子吸收增强和阴影效应时，该分析还扩展到考虑了过滤器纤维对粒子吸收的散射。