Jaoui Mohammed, Urbanski Shawn P, Long Russell W, Landis Matthew S
US EPA, Office of Research and Development, Research Triangle Park, NC, USA.
U.S.D.A. Forest Service, Rocky Mountain Research Station, Missoula, MT, USA.
Environ Chem. 2024 Jan 22;20(8):319-338. doi: 10.1071/en23013.
Pine needles represent an important fuel source in coniferous forest systems in the western United States. During forest fires, they can be easily ignited and help sustain flame on the ground. In this study, a comprehensive chemical analysis was conducted to examine oxygenated organic compounds (OOCs) present in PM formed from burning dry and moist ponderosa pine needles (PPN) in the presence and absence of fine woody debris (FWD). The effect of fuel moisture content (FMC), a key parameter that influence smoke formation, has not received much attention. Therefore, we also investigated the effect of FMC on PM formation and its composition. Thirty three experiments were conducted at the US Forest Service Fire Science Laboratory. PM was collected onto 47 mm Teflon filters, and silylated extracts were analyzed by gas chromatography-mass spectrometry. More than fifty OOCs were identified, including levoglucosan and mannosan; n-dodecanoic acid and n-hexadecanoic acid; dihydroabietic acid, and dehydroabietic acid; and a series of intermediate volatile and semivolatile organic compounds. Mass spectra of a wide variety of compounds in electron and chemical ionization mode are provided. Most of these OOCs were identified in this study for the first time in PPN aerosol, although some were previously reported in pine wood and other biomass burning aerosol. Our results show significant changes in the composition and abundance of particles depending on the amount and type of PPN burned. When compared with dry PPN condition, moist PPN showed decreased emissions of PM and OOCs, due likely to the presence of water in the system that partially suppressed the production of OOCs. Incorporating pine needles in atmospheric models as a contributor to smoke particles generated during forest fires is an essential step towards reducing the current uncertainties regarding the influence of these aerosols on chemical/air mass characteristics, regional meteorology, and the climate.
在美国西部的针叶林系统中，松针是一种重要的燃料来源。在森林火灾期间，它们很容易被点燃，并有助于维持地面火焰。在本研究中，进行了一项全面的化学分析，以检测在有和没有细木屑（FWD）的情况下，燃烧干燥和潮湿的黄松针（PPN）所形成的颗粒物（PM）中存在的含氧有机化合物（OOCs）。燃料含水量（FMC）是影响烟雾形成的一个关键参数，但其影响尚未得到足够关注。因此，我们还研究了FMC对PM形成及其成分的影响。在美国林业局火灾科学实验室进行了33次实验。将PM收集到47毫米的特氟龙滤膜上，并用气相色谱-质谱联用仪分析硅烷化提取物。鉴定出了五十多种OOCs，包括左旋葡聚糖和甘露聚糖；正十二烷酸和正十六烷酸；二氢枞酸和脱氢枞酸；以及一系列中间挥发性和半挥发性有机化合物。提供了多种化合物在电子电离和化学电离模式下的质谱图。这些OOCs中的大多数在本研究中首次在PPN气溶胶中被鉴定出来，尽管之前在松木和其他生物质燃烧气溶胶中已有报道。我们的结果表明，根据燃烧的PPN的数量和类型，颗粒物的成分和丰度会发生显著变化。与干燥PPN条件相比，潮湿PPN的PM和OOCs排放量降低，这可能是由于系统中存在水分，部分抑制了OOCs的产生。将松针纳入大气模型，作为森林火灾期间产生的烟雾颗粒的一个来源，是减少目前关于这些气溶胶对化学/空气质量特征、区域气象和气候影响的不确定性的重要一步。
