AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Source Apportionment and Mass Measurement of Fine Particulate Matter Arising from Massive Southern Oregon and Northern California Fires during the Summer of 2018
DAVID GOBELI, Jennifer Brown, George Allen, Met One Instruments, Incorporated
Abstract Number: 94 Working Group: Biomass Combustion: Emissions, Chemistry, Air Quality, Climate, and Human Health
Abstract Black carbon “BC”, brown carbon “BrC”, and continuous gravimetric PM2.5 were measured in Grants Pass Oregon during a series of devastating, lightning induced wildfires in southern Oregon and northern California during the summer and fall of 2018. The equipment was set up at a monitoring site which at times was within a few miles of one or more of the active fires. BC and BrC were measured using portable and rack-mounted, tape-based carbon monitors of two and ten illumination wavelengths respectively. Total mass in the form of PM2.5 was continuously measured during the event using a class 3 US-EPA designated beta attenuation mass monitor “BAM” and a high-temporal resolution optical PM monitor. All monitors were collocated. Monitoring results reveal very good correlation between BrC and PM2.5 and fair to good correlation between BC and PM2.5. BC, measured at 950 nm was typically 2-5% of gravimetric PM2.5. BC, which is normally present in low concentrations (< 0.300 μg/m3) because of the low population density of the region was measured at concentrations approaching 10 μg/m3 during the event. BrC, which is normally almost non-existent in the region during the summer months, except in cases of forest fires, was recorded at concentrations close to 50 μg/m3 using UV (370 nm) illumination only. Sandradewi’s and other methods for source apportionment were also evaluated using different combinations of illumination wavelengths, and equivalent black carbon “EBC” wavelengths. Wide variations in the BrC/EBC fractions were observed at the commonly used 470 nm/950 nm illumination combination over time, perhaps because of varying distances between active fire events and the fixed monitoring sites. In addition, wide variations were noted in the differences between reported BrC/EBC fraction as a function of UV and IR illumination wavelength combinations.