In Situ and Laboratory Observations from the 2023 Canadian Wildfires Smoke Transported into the United States

During the summer of 2023, the smoke produced by Canadian wildfires reached the northeastern United States, causing unprecedentedly unhealthy air quality levels across the region. In Baltimore, MD, the Air Quality Index (AQI) exceeded values above 200, classified as “very unhealthy”.

In situ filter collection and in situ observations of ambient air were taken at the University of Maryland, Baltimore County (UMBC) during two major events on June 8-9th and June 28-29th. The UMBC Polarized Imaging Nephelometer (PI-Neph) was used to measure the aerosol phase function. These observations alongside the Generalized Retrieval of Aerosol and Surface Properties (GRASP) inversion algorithm, were utilized to derive the microphysical properties of the ambient aerosol. Simultaneously, filter samples of the same particles passing through the PI-Neph were obtained, and additional analyses to characterize aerosol type, morphology, and optical properties were obtained by Scanning Electron Microscopy (SEM).

We will present the outcomes of this study and discuss the differences found in the polarized phase function between the two events, as well as the overall contribution of the Canadian wildfires' smoke superimposed to the local bioaerosol particles.