Aerosol Mass and Optical Properties, Smoke Influence on O 3 , and High NO 3 Production Rates in a Western U.S. City Impacted by Wildfires
Aerosol Mass and Optical Properties, Smoke Influence on O 3 , and High NO 3 Production Rates in a Western U.S. City Impacted by Wildfires
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受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 O 3 的影响以及高 NO 3 生产率
DOI：
10.1029/2020jd032791
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
Coefield, Sarah
中科院分区：
文献类型：
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作者：
Selimovic, Vanessa;Yokelson, Robert J.;McMeeking, Gavin R.;Coefield, Sarah
评估我们对野火和指定火灾产生的烟雾的理解可以受益于顺风测量，包括测试生产和运输的惰性示踪剂和测试化学机制的活性物质。我们在蒙大拿州米苏拉的地面站对针叶林燃料火灾产生的烟雾进行了两个夏天（2017年和2018年）>1,000小时的特征分析，并发现关键属性的范围很窄。ΔPM2.5/ΔCO为0.1070 ± 0.0278（g/g），约为在自由对流层高度下获得的与年龄无关的比值（0.2348 ± 0.0326）的一半。这两年的平均吸收率指数为1.84 ± 0.18，约为非常新鲜烟雾的一半。棕色碳（BrC）是持久的（约50%的吸收在401 nm）在这两年，尽管烟龄的差异。从2017年到2018年，ΔBC/ΔCO翻了一番，但两年的平均值在最近空气测量值的33%以内，表明平台之间的采样偏差较低。从1.0微米切换到2.5微米的截止值增加了质量散射和质量吸收系数，这表明经常被忽视的超微米颗粒影响中度老化烟雾的光学特性。当野火烟雾存在时，O3在整个昼夜期间平均升高约6 ppb，并且与烟雾相关的O3增加在夜间最高（约9 pbb），这表明大量的逆风生产。NOx主要来源于本地。NOx刺激了高速率的NO3产生，包括野火烟雾（高达2.44 ppb hr−1）和至少一个夜间BrC次级形成事件，可能会影响第二天的光化学。
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. ΔPM2.5/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. O3was elevated ~6 ppb on average over a full diurnal period when wildfire smoke was present, and smoke‐associated O3increases were highest (~9 pbb) at night, suggesting substantial upwind production. NOxwas mostly local in origin. NOxspurred high rates of NO3production, 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.