Investigation of high ozone events due to wildfire smoke in an urban area. (December 2018)

• Record Type: Journal Article
• Authors: McClure, Crystal D.; Jaffe, Daniel A.
• Is Part Of: Atmospheric environment. Volume 194(2018)
• Page Start: 146
• Page End: 157
• Publication Date: 2018-12
• Subjects: Wildfires -- Biomass burning -- PAN -- Generalized additive model -- Ozone -- Enhancement ratios; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2018.09.021
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: Using data from the St. Luke's site in Meridian, ID (near Boise) during 2006–2017 and a 2017 summer intensive campaign, we investigate enhancements in ozone (O3 ) during wildfire events in an urban area. We calculate a wildfire criterion based on the National Oceanic and Atmospheric Administration (NOAA) National Environmental Satellite, Data, and Information Service (NESDIS) Hazard Mapping System (HMS) smoke product and historically averaged PM2.5 data to determine when wildfire emissions are influencing the area (smoke vs. non-smoke events). We also use a Generalized Additive Model (GAM) to investigate anomalous sources of O3, such as wildfires, in this urban area. During the summer 2017 intensive campaign, we find that peroxyacetyl nitrate (PAN), reactive nitrogen (NOy ), and maximum daily 8 h average (MDA8) O3 show significant enhancements during smoke events compared with non-smoke periods (65%, 42%, and 32%, respectively). We calculate the 95% confidence interval of ΔPM2.5 /ΔCO, ΔNOy /ΔCO, ΔPAN/ΔNOy, and ΔPAN/ΔCO enhancement ratios (ERs) to be 0.129–0.144 μg/m 3 /ppbv, 0.018–0.022 ppbv/ppbv, 0.152–0.192 ppbv/ppbv, and 3.04–3.76 ppbv/ppmv, respectively, for wildfire smoke influenced events. We also observe an enhancement in O3 production up to PM2.5 concentrations of 60–70 μg/m 3 in smoke, after which we see a reduction in average MDA8 O3 mixing ratios. We use the four highest O3 events during summer 2017 as case studies to examine the highly variable conditions due to the influence of wildfire smoke in an urban area. In two cases, we investigate smoke days that show significant O3 enhancement and moderate PM2.5 concentrations. These cases suggest that ERs, such as ΔPM2.5 /ΔCO and ΔNOy /ΔCO, are less useful in determining the influence of wildfire smoke in an urban area on moderate smoke days. Another case shows reduced O3 production during a very high, 3-day smoke event (PM2.5 > 70 μg/m 3 ). After this high smoke period, a 20 ppbv enhancement in MDA8 O3 is observed in moderate smoke. These results indicate that wildfire-influenced O3 enhancements are highly variable in urban areas but generally increase up to around 60 μg/m 3 of PM2.5, after which they decrease at very high smoke concentrations. This study also suggests that multiple tracer measurements are needed to fully characterize wildfire plumes in urban areas. Graphical abstract: Highlights: Effects on high ozone events due to wildfire emissions are studied in Boise, ID. PAN, NOy, and MDA8 O3 show significant enhancements during smoke periods. PM, NOy, and PAN smoke enhancement ratios are characterized for an urban area. At high smoke concentrations, average MDA8 O3 mixing ratios are reduced.