AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Hunting Sources of Biogenic Ice Nucleating Particles in Soils, Sea Spray and Air
PAUL DEMOTT, Thomas Hill, Yukata Tobo, Christina S. McCluskey, Ezra Levin, Kaitlyn Suski, Douglas Collins, Gavin Cornwell, Christopher Lee, Camille Sultana, Jessica Axson, Francesca Malfatti, Kimberly Prather, Sonia Kreidenweis, Tinkara Tinta, Colorado State University
Abstract Number: 426 Working Group: Bioaerosols
Abstract We posit that an important proportion of ice nucleating particles (INP) in air that have previously been distinguished only as having a carbonaceous source have biogenic sources. These INP may include microbes and organic materials that are products of biological activity. This study describes efforts toward defining the numbers and compositions of biogenic INP in air, their general sources from soils and oceans, and their compositions.
Complementary real-time and offline measurement methods are applied. Measurements with a continuous flow diffusion chamber allow for isolation of INP via impaction for electron microscopic examination, and linking to a single particle time-of-flight aerosol mass spectrometer via a pumped counterflow virtual impactor for real-time compositional analyses. Offline immersion freezing methods following collection of particles onto substrates or directly into liquid provide for large sample volume assessment of INP number concentrations, extending the measurable range over several orders of magnitude and 35 C supercooling. Filtration, heat, and chemical treatment permit exploring the size and relative organic content of INP.
Arable soils are strong potential sources for atmospheric biogenic INP of at least three types. At warmer than about -12 C, microbial INP can sometimes dominate. At lower temperatures, unidentified stable organic materials dominate as INP. Clay mineral particles are the least effective particles contained in arable soils, unlike desert soils where mineral particles dominate INP.
Marine aerosol INP studies are exploiting realistic sea spray generation in the laboratory and sampling from the marine boundary layer. A certain category of sea salt particles is often associated with ice nuclei of marine origin, but detailed investigations of the ice nucleating “units” within seawater and the sea surface microlayer indicate that these INP are often between 20 and 200 nm in size. Continuing studies to isolate the compositions of these INP as bacterial, viral, or simply molecular will be described.