CM-BIN

Continuous Measurements of Biological Ice Nuclei

1 October 2025 - 30 September 2028

Lead Scientist: Gavin Cornwell

Observatory: AMF

Bioparticles, despite their low atmospheric burden, are of particular interest due to their ability to nucleate ice at exceptionally warm temperatures (> -15 °C). Bio-ice nucleating particles (INPs) are hypothesized to have an outsized effect on clouds because they can initiate freezing at temperatures warm enough for important secondary ice production processes to activate, leading to the rapid glaciation of the cloud at temperatures where primary ice nucleation alone could not.

Bio-INPs are typically treated as a single class, even though laboratory studies have shown that different bioparticle types (e.g., fungal spores, bacteria, pollen, etc.) exhibit highly variable IN activities. This discrepancy can be attributed to the difficulty in characterizing and quantifying bio-INP types. For example, the most prevalent method for quantifying bio-INPs is through treatment-based methods that use the change in a sample’s IN activity after being exposed to heat, hydrogen peroxide, or enzymes to infer the inactivation of bio-INPs. These methods are useful for providing rough estimates of bio-INP concentrations but cannot not yield insight into the identity or activities of bio-INPs from different bioparticle types.

The project will deploy to the AMF3 deployment to the Bankhead National Forest (BNF) to collect measurements of single particle composition using a single particle mass spectrometer (SPMS). The project will also collect samples for offline analysis of composition by electron microscopy and ice nucleating particle concentrations using a droplet freezing assay method. This project will calculate bio-INP concentrations from these measurements. Ice nucleation activities for different bioparticle types will be calculated for each particle type empirically, constrained by the bio-INP concentrations. This campaign will greatly improve our understanding the degree to which bioparticles, along with which types of bioparticles, drive ambient INP concentrations and variability.