ADVANCED MEASUREMENTS OF UNDERSAMPLED GLOBALLY SIGNIFICANT BIOMASS BURNING SOURCES

During the fourth Fire Lab at Missoula Experiment (FLAME-4) laboratory campaign, we burned historically undersampled and globally significant biomass fuels. The open-path Fourier transform infrared (OP-FTIR) spectroscopy system provided new emissions data while measuring gases that overlap with fire emissions measured in numerous field campaigns. Based on the lab-field comparisons, we conclude that our lab-measured emission factors (EFs) for some of the fires can be adjusted to better represent typical open burning. In addition we deployed a high-resolution proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) to characterize biomass burning (BB) emissions for the first time. BB is the second largest global atmospheric source of gas-phase non-methane organic compounds (NMOCs) and a significant portion of the higher molecular weight species remains unidentified including intermediate and semi-volatile organic compounds (I/SVOCs). Realistic estimates of I/SVOC emissions from BB sources are vital to advance current understanding of air quality and climate impacts (particularly secondary organic aerosol and photochemical ozone production).Using several approaches we were able to assign the most probable identities to most major exact masses, including I/SVOCs. Approximately 80-96% of the total NMOC mass detected by the PTR-TOF-MS and FTIR was positively or tentatively identified compared to 30-70% in previous large-scale studies. We report data for many rarely measured or previously unmeasured emissions in several compound classes that are likely secondary organic aerosol precursors. The Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE) campaign targeted source characterization of numerous important but undersampled (and often inefficient) combustion sources that are widespread in the developing world such as brick kilns, wood and dung cooking fires, crop residue and garbage burning, generators, irrigation pumps, and motorcycles. We report the trace gas and aerosol measurements obtained by FTIR spectroscopy, whole air sampling, and photoacoustic extinctiometers based on the NAMaSTE field work. The trace gas measurements are the most comprehensive to date for these sources and the light absorption by both black and brown carbon was important for many sources. The NAMaSTE data will significantly enhance regional-global chemistry and climate modeling