Characterizing Particulate Matter Impacts of Smoke From 2022 to 2023 Agricultural Burning in South Florida

Smoke from agricultural fires is a potentially important source of fine particulate matter (PM_2.5) in the US. Sugarcane is burned in Florida to facilitate the harvesting process, with the majority of these fires occurring in the Everglades Agricultural Area (EAA), where there is only one regulatory air quality monitor. During the 2022-2023 sugarcane burning season (October-May), we used public low-cost PurpleAir sensors, regulatory monitors, and 29 PurpleAir sensors deployed for this study to quantify PM_2.5 from agricultural fires. We found satellite imagery is of limited use for detecting smoke from agricultural fires in Florida due to the cloud cover, overnight smoke, and the fires being small and short-lived. For these reasons, surface measurements are critical for capturing increases in PM_2.5 from smoke, and we used multiple smoke-identification criteria. During the study period, median 24-hour PM_2.5 concentrations increased by 2.3-6.9 μg m^-3 on smoke-impacted days compared to unimpacted days, with smoke observed on 4%-28% of the campaign days (ranges from the different smoke-identification criteria). Further, short-term PM_2.5 increases were observed over 40 μg m^-3 during smoke events. We contrast the region near the EAA with large populations of low-income and minoritized groups to the more affluent coastal region. The inland region experienced more smoke-impacted monitor days than the Florida east coast region, and there was a higher study-average smoke PM_2.5 concentration in the inland area. These findings highlight the need to increase air quality monitoring near the EAA.