Evaluating our understanding of smoke from wild and prescribed fires can benefit from downwind measurements that include inert tracers to test production and transport and reactive species to test chemical mechanisms. We characterized smoke from fires in coniferous forest fuels for >1,000 hr over two summers (2017 and 2018) at our Missoula, Montana, surface station and found a narrow range for key properties. ΔPM_2.5/ΔCO was 0.1070 ± 0.0278 (g/g) or about half the age‐independent ratios obtained at free troposphere elevations (0.2348 ± 0.0326). The average absorption Ångström exponent across both years was 1.84 ± 0.18, or about half the values available for very fresh smoke. Brown carbon (BrC) was persistent (~50% of absorption at 401 nm) in both years, despite differences in smoke age. ΔBC/ΔCO doubled from 2017 to 2018, but the average across 2 years was within 33% of recent airborne measurements, suggesting low sampling bias among platforms. Switching from a 1.0 to a 2.5 micron cutoff increased the mass scattering and mass absorption coefficients, suggesting often overlooked supermicron particles impact the optical properties of moderately aged smoke. O₃ was elevated ~6 ppb on average over a full diurnal period when wildfire smoke was present, and smoke‐associated O₃ increases were highest (~9 pbb) at night, suggesting substantial upwind production. NO_x was mostly local in origin. NO_x spurred high rates of NO₃ production, including in the presence of wildfire smoke (up to 2.44 ppb hr⁻¹) and at least one nighttime BrC secondary formation event that could have impacted next‐day photochemistry.

中文翻译：

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受到野火影响的美国西部城市的气溶胶质量和光学特性，烟雾对O3的影响以及NO3的高生产率

评估我们对野火和明火产生的烟雾的理解可以从顺风测量中受益，顺风测量包括用于测试生产和运输的惰性示踪剂以及用于测试化学机理的反应性物种。在两个夏天（2017年和2018年），我们在蒙大拿州米苏拉地面站对针叶林燃料中的火灾产生的烟尘进行了超过1,000小时的表征，发现关键性能的范围很窄。ΔPM _2.5/ΔCO为0.1070±0.0278（g / g），约为在对流层自由高度（0.2348±0.0326）时获得的与年龄无关的比率的一半。两年间的平均吸收Ångström指数为1.84±0.18，约为极新鲜烟雾可利用值的一半。尽管吸烟年龄有所不同，但在这两年中，褐碳（BrC）一直存在（在401 nm处约50％的吸收）。从2017年到2018年，ΔBC/ΔCO翻了一番，但两年的平均值在近期机载测量值的33％以内，表明平台之间的采样偏差较低。从1.0微米的截止值切换到2.5微米的截止值会增加质量散射和质量吸收系数，表明经常被忽略的超微粒子会影响中度老化烟雾的光学特性。Ø ₃当存在野火烟雾时，在整个昼夜期间平均升高〜6 ppb，而与烟雾相关的O ₃夜间增加最高（〜9 pbb），表明大量逆风产生。NO _x大部分是本地来源的。NO _x刺激了NO _3的高产生，包括在野火烟雾（高达2.44 ppb hr ^-1）的存在下，以及至少一个夜间的BrC次级形成事件，这些事件可能会影响第二天的光化学反应。