Estimation of Possible Primary Biological Particle Emissions and Rupture Events at the Southern Great Plains ARM Site

Abstract

We use 10 years of data from the Department of Energy (DoE) Atmospheric Radiation Measurements (ARM) United States Southern Great Plains (SGP) site with nearby regional pollen and fungal spore measurements to indirectly estimate the seasonal influence of these two primary biological aerosol particles (PBAP). We estimate possible primary emissions of larger PBAP and PBAP rupture events, which form submicron organic aerosol during precipitation or high relative humidity. High pollen counts at two urban stations near SGP occur during late winter/early spring (day of year (DOY) 50–120) and late summer (DOY 240–310). Around 4–19 days per year show possible pollen events (PPE) when near‐surface lidar observations of daily linear particle depolarization ratio >0.1 are coincident with high organic aerosol fraction. For PPE days with rainfall, aerosol size distribution observations show enhanced submicron particle concentrations consistent with pollen rupture events. For fungal spores, high fungal spore counts occur during late spring/early summer (DOY 110–195) and late summer/autumn (DOY 220–340). Based on size distribution observations, up to 7% of days have possible fungal spore rupture events (PFE) with higher aerosol number count specifically over the range expected for fungal spore fragment mobility diameter (20–50 nm). These short‐lived PFE correlate with rainfall or occur after prolonged exposure to rainfall (e.g., >10 h). While the SGP site lacks direct measurements of bioaerosol and large particle sizes, this analysis suggests that PBAP primary emissions and rupture events could occur about 32 days per year, representing an important component of the aerosol budget during seasonal emissions.Plain Language SummaryPrimary biological aerosol particles (PBAP) are emitted directly from the Earth’s surface and can include pollen, fungal spores, and bacteria. They can act as nuclei for water droplets or ice crystals and are known to impact clouds and precipitation, and may influence both the regional and the global climate and hydrological cycle. Because measurements of many PBAPs are sparse, we use a suite of atmospheric data from the ambient aerosol and meteorological measurements from the Department of Energy’s Atmospheric Radiation Measurements at United States Southern Great Plains site to indirectly identify possible emissions of pollen and fungal spores from the land surface. We estimate that PBAP can contribute to the local aerosol burden, especially during their peak emission periods.Key PointsAn average of 12 days per year are estimated as primary pollen event days with high interannual variabilityDuring primary pollen events with precipitation or high humidity, rupture events are indicated during ∼4 days per yearDuring or after the prolonged exposure of rainfall for >10 h, ∼20 days per year show evidence of fungal spore rupture events