Impact of Wildfires on Ozone Exceptional Events in the Western US
Impact of Wildfires on Ozone Exceptional Events in the Western US
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DOI：
10.1021/es402164f
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发表时间：
2013-10-01
影响因子：
11.4
通讯作者：
Reid, Stephen B.
中科院分区：
文献类型：
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作者：
Jaffe, Daniel A.;Wigder, Nicole;Reid, Stephen B.
野火产生大量的氮氧化物（NOx）和挥发性有机化合物（VOC）排放。因此，野火有助于大气中臭氧（O-3）的升高。然而，有一个很大的变化量的O-3前体的排放量和火灾之间产生的O-3的量。在美国西部，O-3、有机碳和卫星衍生的一氧化碳混合比的中位数也存在显著的年际变化。为了更好地了解野火产生的O-3，我们开发了一个统计模型，估计美国西部三个城市地区的最大日8小时平均（MDA 8）O-3作为几个气象和时间变量的函数：湖城UT;博伊西，ID;和里诺，NV。该模型使用2000年6月至2012年9月的数据开发。对于这三个位置，统计模型可以解释每日MDA变化的60%、52%和27% 8。统计模型残差（SMR）可以提供关于通常气象模式无法解释的O-3其他来源的信息。几种可能的O-3来源可以解释任何一天的高SMR值。我们研究了几种情况下，高SMR是由于野火的影响。考虑的第一个案例是2008年6月里诺的MDA 8达到82 ppbv。野火对这一事件的影响得到了PM浓度、当时野火的已知位置以及天气和研究预测模型与化学（WRF-Chem）的模拟的支持，该模型表明从加州的大火燃烧到里诺的运输。根据SMR，估计加州野火对里诺的MDA 8的贡献为26 ppbv，根据WRF-Chem，估计为60 ppbv。WRF-Chem模型还表明过氧乙酰硝酸酯（PAN）在从加州野火运输过程中产生O-3的重要作用。我们假设，增强PAN由于野火排放可能会导致区域增强O-3在火灾高发年。第二例病例发生在2012年8月的湖城（SLC）地区。在此期间，MDA 8达到83 ppbv，SMR表明野火对MDA 8的贡献为19 ppbv。野火的影响是支持PM2.5数据，野火的时间，HYSPLIT分散模型，表明运输从火灾在爱达荷州，并从CMAQ模型的结果，确认火灾的影响。在此期间，PM2.5和O-3的浓度有所提高，但总体而言，它们之间的关系很差，这与O-3的二次生产的复杂性是一致的。第三个病例在2012年7月期间在ID的博伊西观察了高MDA 8，并得出了类似的结论。这些结果支持使用统计建模作为一种工具来量化野火对城市O-3浓度的影响。
Wildfires generate substantial emissions of nitrogen oxides (NOx) and volatile organic compounds (VOCs). As such, wildfires contribute to elevated ozone (O-3) in the atmosphere. However, there is a large amount of variability in the emissions of O-3 precursors and the amount of O-3 produced between fires. There is also significant interannual variability as seen in median O-3, organic carbon and satellite derived carbon monoxide mixing ratios in the western U.S. To better understand O-3 produced from wildfires, we developed a statistical model that estimates the maximum daily 8 h average (MDA8) O-3 as a function of several meteorological and temporal variables for three urban areas in the western U.S.: Salt Lake City, UT; Boise, ID; and Reno, NV. The model is developed using data from June-September 2000-2012. For these three locations, the statistical model can explain 60, 52, and 27% of the variability in daily MDA8. The Statistical Model Residual (SMR) can give information on additional sources of O-3 that are not explained by the usual meteorological pattern. Several possible O-3 sources can explain high SMR values on any given day. We examine several cases with high SMR that are due to wildfire influence. The first case considered is for Reno in June 2008 when the MDA8 reached 82 ppbv. The wildfire influence for this episode is supported by PM concentrations, the known location of wildfires at the time and simulations with the Weather and Research Forecasting Model with Chemistry (WRF-Chem) which indicates transport to Reno from large fires burning in California. The contribution to the MDA8 in Reno from the California wildfires is estimated to be 26 ppbv, based on the SMR, and 60 ppbv, based on WRF-Chem. The WRF-Chem model also indicates an important role for peroxyacetyl nitrate (PAN) in producing O-3 during transport from the California wildfires. We hypothesize that enhancements in PAN due to wildfire emissions may lead to regional enhancements in O-3 during high fire years. The second case is for the Salt Lake City (SLC) region for August 2012. During this period the MDA8 reached 83 ppbv and the SMR suggests a wildfire contribution of 19 ppbv to the MDA8. The wildfire influence is supported by PM2.5 data, the known location of wildfires at the time, HYSPLIT dispersion modeling that indicates transport from fires in Idaho, and results from the CMAQ model that confirm the fire impacts. Concentrations of PM2.5 and O-3 are enhanced during this period, but overall there is a poor relationship between them, which is consistent with the complexities in the secondary production of O-3. A third case looks at high MDA8 in Boise, ID, during July 2012 and reaches similar conclusions. These results support the use of statistical modeling as a tool to quantify the influence from wildfires on urban O-3 concentrations.