Pollen and Spores and Bits, Oh My

Published: 15 March 2022

A Michigan researcher taps long-term ARM data for insights into ‘natural emissions’

The University of Michigan’s Allison Steiner investigates tiny particles of plant matter that influence clouds and weather. Photo is courtesy of the University of Michigan.

Allison L. Steiner teaches and leads a research team at the University of Michigan, where she designs models of the land-atmosphere interface. In her research, she has started to analyze more data from the Atmospheric Radiation Measurement (ARM) user facility. Her interests include regional weather systems, boundary-layer meteorology, algae blooms, and aerosolized water-spray emissions on the Great Lakes.

But the heart of Steiner’s work relates to how bits of vegetation swept into the atmosphere affect climate, cloud formation, and weather. Such biological particles are “natural emissions” that hint at pre-industrial air quality, she says.

They are also the main study targets of a project Steiner leads, with funding from the Atmospheric System Research (ASR) program within the U.S. Department of Energy (DOE). She is particularly interested in microscopic fungal spores or pollen from trees, grasses, and weeds.

During rainfall events, or even episodes of high relative humidity, increased osmotic pressure can cause pollen to swell and rupture. That can suddenly turn one particle into hundreds or thousands.

Such “rupture events” disperse submicron particles as small as 30 nanometers wide. (For pollen, these bits are mostly starch granules.) These events were the subject of a landmark 2020 paper on aerosol nanoparticles released by fungi in periodic bursts. The study used observations from ARM’s Southern Great Plains (SGP) atmospheric observatory.

The first paper to come out of Steiner’s ASR project also drew on SGP assets―in this case, 10 years of extensive aerosol data. The study, with Michigan research fellow Tamanna Subba as lead author, appeared in August 2021. It modeled estimates of particle rupture events, as well as particle emissions.

Steiner’s interest in land-atmosphere interactions adds another ARM twist to her story. She is part of a science team designing a plan for deploying an ARM mobile observatory in the Southeastern United States. It will operate for five years, starting in 2023.

Read more about Steiner in this ASR profile.

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Author: Corydon Ireland, Staff Writer, Pacific Northwest National Laboratory

ARM is a DOE Office of Science user facility operated by nine DOE national laboratories.