Identification of burning influenced fine aerosol samples in a monitoring network using mid-infrared spectroscopy

Abstract:

Organic mass is a major constituent of fine particulate matter and contributes significantly to degradation of visibility, radiative forcing, and causes adverse health effects. However, its composition, formation mechanisms, and adverse health effects are not fully characterized due to its sheer compositional complexity. Biomass burning (e.g., residential wood burning, wildfires, and prescribed burning) is a major source of primary and secondary OM that is gaining an ever-increasing importance due to increased wildfire activities around the world.

In this study, we introduce a new method for identification of burning-influenced samples at selected sites of the Inter-agency Monitoring of PROtected Visual Environments (IMPROVE) network using mid-infrared spectra – acquired non-destructively from Teflon filters used for fine particulate matter quantification. This method, which uses the mid-infrared fingerprint signatures of biomass burning tracers (i.e., levoglucosan and lignin) for the first, identifies samples in the places and periods of known wildfires and residential wood burning and agrees well with previous identification methods functioning based on mid-infrared spectral similarity (e.g., cluster analysis). In addition, this method identifies samples with high probability of being influenced by burning that were not detected by previous methods.

Finally, we use our knowledge of functional group evolution of biomass burning aerosols with aging, from environmental chamber experiments and the atmosphere, in tandem with mid-infrared signatures of lignin and levoglucosan to better understand the contribution of biomass burning aerosols (fresh and aged) to the total fine particulate matter (PM). This work is supplementary to previous studies (often using aerosol mass spectrometry), which only considered fresh biomass burning aerosol contribution to the total PM.