More Like this

1. Wildfire smoke reduces lake ecosystem metabolic rates unequally across a trophic gradient

   https://doi.org/10.1038/s43247-024-01404-9  

   Smits, Adrianne P; Scordo, Facundo; Tang, Minmeng; Cortés, Alicia; Farruggia, Mary Jade; Culpepper, Joshua; Chandra, Sudeep; Jin, Yufang; Valbuena, Sergio A; Watanabe, Shohei; et al (December 2024, Communications Earth & Environment)

   Abstract Wildfire smoke covers entire continents, depositing aerosols and reducing solar radiation fluxes to millions of freshwater ecosystems, yet little is known about impacts on lakes. Here, we quantified trends in the spatial extent of smoke cover in California, USA, and assessed responses of gross primary production and ecosystem respiration to smoke in 10 lakes spanning a gradient in water clarity and nutrient concentrations. From 2006 − 2022, the maximum extent of medium or high-density smoke occurring between June-October increased by 300,000 km². In the three smokiest years (2018, 2020, 2021), lakes experienced 23 − 45 medium or high-density smoke days, characterized by 20% lower shortwave radiation fluxes and five-fold higher atmospheric fine particulate matter concentrations. Ecosystem respiration generally declined during smoke cover, especially in low-nutrient, cold lakes, whereas responses of primary production were more variable. Lake attributes and seasonal timing of wildfires will mediate the effects of smoke on lakes. 

   more » « less
2. Quantifying Wildfire Heavy-Dense Smoke’s Persistent Effects on PM2.5 Speciation across U.S. Regions: Evidence from 2007 to 2023 Smoke Events

   https://doi.org/10.1080/24694452.2026.2681726  

   Zhang, Shiyan; Zhang, Jiakai; Yu, Manzhu (June 2026, Annals of the American Association of Geographers)

   Wildfire smoke substantially degrades air quality by increasing total PM2.5 concentrations and altering their chemical speciation. Although existing research has documented PM2.5 during active fires, the spatiotemporal persistence of these pollutants across U.S. regions remains insufficiently quantified. Leveraging quasi-experimental variation arising from 2007 to 2023 wildfire smoke events, we employ difference-in-differences (DID) and event study approaches to estimate the causal effects on both PM2.5 concentrations and their chemical speciation, while assessing their duration. Our analysis reveals that smoke events increase PM2.5 concentrations by 35 percent nationally, with pronounced regional heterogeneity: Western states experience the most severe impacts (+50 percent persisting for three days), whereas northeastern and southern regions exhibit weaker and shorter lived effects. Chemical speciation analysis reveals distinct temporal dynamics: Heavy metals (chromium, manganese) and inorganic compounds exhibit transient spikes (one day), whereas lead, vanadium, and organic carbon remain elevated for three days. Our findings underscore the urgent need to integrate chemical speciation into air quality monitoring systems to better assess composition-specific health risks under climate-driven intensification of wildfires. 

   more » « less
3. Ultrafine particulate matter in Western US wildfire smoke and their public health risks

   Namyandeh, A; Howell, J; Honeyman, A; Fendorf, S (March 2025, Spring 2025, American Chemical Society Conference)

   Wildfire smoke, particularly particulate matter less than 2.5 microns (PM2.5), represents a major source of air pollution and a growing public health problem. PM2.5 is a general term used for any particulate < 2.5 µm; however, a wide variety of particulates with different physical and chemical properties can be formed in this size range. The health impacts of PMs are controlled by their size. Unlike larger particulates, which only enter the respiratory tract, fine PMs (<0.1 µm) can also enter the bloodstream and even pass through the blood-brain barrier. The health risks due to exposure to PM can be different for various PM phases with different physical properties, which is poorly understood. We collected wildfire smoke from more than 10 major wildfires in the Western US using active air samplers that separate particles in different size ranges (>2.5 µm - <0.25 µm). Particles were collected on filters, which are pre-weighted and loaded into the impactor. The filters were weighted and compared with the pre-weight values to calculate the mass of particles collected at each size range. Our results revealed that for all the smoke from varied wildfires, the mass of particles increased with decreasing size, with the majority (more than 50%) being less than 0.25 μm. In addition, the PM2.5 total concentration was recorded using an air quality monitor and compared to the particle size distribution in different smoke samples. The results showed that as the overall concentration of wildfire smoke decreases, the fraction of particles smaller than 0.250 microns increases even more. This suggests that these ultrafine particles not only make up the majority of PM in wildfire smoke but are also more persistent in the atmosphere, even when the total PM concentration is low. Our findings highlight the magnitude of health risks posed by PM and underscore the urgent need for effective solutions to reduce respiratory exposure in affected communities. 

   more » « less
4. Reactive Nitrogen Partitioning Enhances the Contribution of Canadian Wildfire Plumes to US Ozone Air Quality

   https://doi.org/10.1029/2024GL109369  

   Lin, Meiyun; Horowitz, Larry W; Hu, Lu; Permar, Wade (August 2024, Geophysical Research Letters)

   Quantifying the variable impacts of wildfire smoke on ozone air quality is challenging. Here we use airborne measurements from the 2018 Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN) to parameterize emissions of reactive nitrogen (NOy) from wildfires into peroxyacetyl nitrate (PAN; 37%), NO3− (27%), and NO (36%) in a global chemistry-climate model with 13 km spatial resolution over the contiguous US. The NOy partitioning, compared with emitting all NOy as NO, reduces model ozone bias in near-fire smoke plumes sampled by the aircraft and enhances ozone downwind by 5–10 ppbv when Canadian smoke plumes travel to Washington, Utah, Colorado, and Texas. Using multi-platform observations, we identify the smoke-influenced days with daily maximum 8-hr average (MDA8) ozone of 70–88 ppbv in Kennewick, Salt Lake City, Denver and Dallas. On these days, wildfire smoke enhanced MDA8 ozone by 5–25 ppbv, through ozone produced remotely during plume transport and locally via interactions of smoke plume with urban emissions. 

   more » « less
5. Diversity and distribution of sediment bacteria across an ecological and trophic gradient

   https://doi.org/10.1371/journal.pone.0258079  

   Sauer, Hailey M.; Hamilton, Trinity L.; Anderson, Rika E.; Umbanhowar, Charles E.; Heathcote, Adam J. (March 2022, PLOS ONE)

   Mendoza-Lera, Clara (Ed.)

   The microbial communities of lake sediments have the potential to serve as valuable bioindicators and integrators of watershed land-use and water quality; however, the relative sensitivity of these communities to physio-chemical and geographical parameters must be demonstrated at taxonomic resolutions that are feasible by current sequencing and bioinformatic approaches. The geologically diverse and lake-rich state of Minnesota (USA) is uniquely situated to address this potential because of its variability in ecological region, lake type, and watershed land-use. In this study, we selected twenty lakes with varying physio-chemical properties across four ecological regions of Minnesota. Our objectives were to (i) evaluate the diversity and composition of the bacterial community at the sediment-water interface and (ii) determine how lake location and watershed land-use impact aqueous chemistry and influence bacterial community structure. Our 16S rRNA amplicon data from lake sediment cores, at two depth intervals, data indicate that sediment communities are more likely to cluster by ecological region rather than any individual lake properties ( e . g ., trophic status, total phosphorous concentration, lake depth). However, composition is tied to a given lake, wherein samples from the same core were more alike than samples collected at similar depths across lakes. Our results illustrate the diversity within lake sediment microbial communities and provide insight into relationships between taxonomy, physicochemical, and geographic properties of north temperate lakes. 

   more » « less