We characterized residential biomass burning contributions to fine particle concentrations via multiple methods at Fyfe Elementary School in Las Vegas, Nevada, during January 2008: with levoglucosan on quartz fiber filters; with water soluble potassium (K + ) measured using a particle-into-liquid system with ion chromatography (PILS-IC); and with the fragment C 2 H 4 O 2 + from an Aerodyne High Resolution Aerosol Mass Spectrometer (HR-AMS). A Magee Scientific Aethalometer was also used to

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... ine aerosol absorption at the UV (370 nm) and black carbon (BC, 880 nm) channels, where UV-BC difference is indicative of biomass burning (BB). Levoglucosan and AMS C 2 H 4 O 2 + measurements were strongly correlated (r 2 = 0.92); K + correlated well with C 2 H 4 O 2 + (r 2 = 0.86) during the evening but not during other times. While K + may be an indicator of BB, it is not necessarily a unique tracer, as non-BB sources appear to contribute significantly to K + and can change from day to day. Low correlation was seen between UV-BC difference and other indicators, possibly because of an overwhelming influence of freeway emissions on BC concentrations. Given the sampling location-next to a twelve-lane freeway-urban-scale biomass burning was found to be a surprisingly large source of aerosol: overnight BB organic aerosol contributed between 26% and 33% of the organic aerosol mass.