Wildfire Smoke Chemistry, Impacts, and Interactions with the Atmosphere, Biosphere, and Built Environment

▪ Wildfire events are increasing in intensity and frequency around the globe, and the resulting smoke degrades air quality. Following emission, particulate matter and reactive gases in smoke chemically transform during transport through the near- (hours), mid- (days), and far-field (weeks). The chemical composition of the smoke, its intensity, and subsequent human exposure will vary as a function of not only the properties of the original wildfire but also the subsequent atmospheric chemistry. This chemistry impacts particles, ozone, volatile organic compounds, and other air toxics in urban and rural regions, and thus affects human and ecosystem health. This review synthesizes recent work and identifies key knowledge gaps in the atmospheric chemistry of the smoke plume, smoke composition from fires at the wildland-urban interface, smoke-building interactions and remediation approaches to improve indoor air, and biosphere-atmosphere exchange, including effects on plant productivity and gas exchange. Wildfire smoke is chemically complex with gases and particles that dilute, react, and transform over timescales ranging from minutes to weeks. ▪ Wildfire smoke enhances production of ozone and particulate matter in cities, increasing urban air pollution. ▪ Smoke infiltrates buildings, exposing occupants to pollutants during and after the smoke event, highlighting research needs on wildland-urban interface fires. ▪ Ecosystem productivity can increase or decrease in response to smoke depending on the intensity and location, raising concerns about future crop yield and quality.