A Decadal Climatology of Chemical, Physical, and Optical Properties of Ambient Smoke in the Western and Southeastern United States

Abstract

Biomass burning is a major source of summertime fine particulate matter in the United States, degrading air quality and affecting human health and climate. Fuels, burn conditions, and fire types vary across the United States, which may impact smoke composition and optical properties. We use the Hazard Mapping System to track smoke plumes for 10 years from 2008 to 2017, focusing on three U.S. regions: Southeast, Pacific West, and Southwest. Combining this geospatial data set with AErosol RObotic NETwork (AERONET) columnar data, and Interagency Monitoring of Protected Visual Environments (IMPROVE) network in situ observations, we define "smoke-influenced days" and derive the properties of smoke aerosol for April through September, encompassing the main fire seasons across the United States. We find in the IMPROVE surface measurement that the elemental carbon fraction of smoke in the Southeast is statistically different from and lower than that in the west, consistent with more-smoldering prescribed fires in the southeast. We find in the AERONET columnar observations that the mean single scattering albedo of smoke (at 675 nm) is lower in the two western regions (~0.94) compared to the southeast (~0.96), consistent with the differences in composition and fire types, which implies that the compositional differences at the surface may be representative of the column. Higher relative humidity in the southeast and less dust associated with smoke also appear to contribute to the higher smoke single scattering albedo relative to the west. Our results show that smoke properties vary regionally, with implications for models, data assimilation, and remote-sensing.

Biomass Burning Over the United States East Coast and Western North Atlantic Ocean: Implications for Clouds and Air Quality

“…The strong SO₄ 2− enhancement on BB days is noteworthy as Bian et al. (2020) previously showed that smoke in the southeast U.S. has a higher SO₄ 2− fraction than smoke over the western U.S. Furthermore, Bian et al.…”

Estimated Mortality and Morbidity Attributable to Smoke Plumes in the United States: Not Just a Western US Problem

“…Volume size distributions of smoke aerosol from Bian et al. ( 2020 ) indicate that <5% of PM 2.5 volume (and hence mass) exists in the diameter range of 1–2.5 µm, thus errors due to this assumption are <5%, smaller than the relative uncertainty from the concentration response function. Further, we assumed that the WE‐CAN HAPs to PM 1 ratios are representative of all US smoke plumes, but smoke HAPs concentrations may vary by fuel type (e.g., Gilman et al., 2015 ), burn conditions (Sekimoto et al., 2018 ), and smoke age (O’Dell et al., 2020 ).…”

“…Thus, in order to use these HAP to PM1 ratios with our krigged smoke PM2.5 estimates, we assumed the mass concentration of particles with diameters betweeen 1 µm and 2.5 µm was negligible. Volume size distributions of smoke aerosol from Bian et al (2020) indicate that <5% of PM2.5 volume (and hence mass) exists in the diameter range of 1-2.5 µm, thus errors…”

Weekend‐Weekday Implications and the Impact of Wildfire Smoke on Ozone and Its Precursors at Boulder Reservoir, Colorado Between 2017 and 2019

“…To compare HAPs to PM 2.5 ratios at Boulder Reservoir to those reported in O'Dell et al (2020), which are to PM 1 mass, we assume mass contribution from smoke particles with diameters between 1 and 2.5 µm is negligible. Volume size distributions (which are directly proportional to mass size distributions under constant particle density) from (Bian et al, 2020) indicate particles of diameter range 1-2.5 µm contribute <5% of total PM 2.5 volume in smoke. We find the distribution of benzene to PM 2.5 ratios during smoke impacted periods at Boulder Reservoir to be similar to those reported in O'Dell et al (2020); however, ratios of toluene and hexane to PM 2.5 at Boulder Reservoir are higher than O'Dell et al (2020).…”