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Laboratory measurements of immersion freezing abilities of non-proteinaceous and proteinaceous biological particulate proxies
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  • Kimberly Cory,
  • Joshua Mills,
  • Yutaka Tobo,
  • Kotaro Murata,
  • Kumiko Goto-Azuma,
  • Craig Whiteside,
  • Bobby McCauley,
  • Carolyn Bouma,
  • Naruki Hiranuma
Kimberly Cory
West Texas A&M University
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Joshua Mills
West Texas A&M University
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Yutaka Tobo
National Institute of Polar Research
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Kotaro Murata
National Institute of Polar Research
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Kumiko Goto-Azuma
National Institute of Polar Research
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Craig Whiteside
West Texas A&M University
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Bobby McCauley
West Texas A&M University
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Carolyn Bouma
West Texas A&M University
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Naruki Hiranuma
West Texas A&M University

Corresponding Author:[email protected]

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Abstract

Non-proteinaceous and proteinaceous biological aerosols are abundant within the atmosphere and have the potential to impact the climate through cloud and precipitation formation. In this study, we present the differences in the laboratory-measured freezing capabilities of the non-proteinaceous and proteinaceous biological materials to determine which has more potential to impact the ice nucleation in the clouds. As non-proteinaceous surrogates, we examined multiple cellulose materials (e.g., microcrystalline and nanocrystalline cellulose) whose sizes range from ~100 nm to >100 μm (according to manufacturer report). For proteinaceous proxies, we looked at different gram-negative bacteria, such as Pseudamonas aeruginosa, Escherichia coli, Serratia marcescens, Citrobacter freundii, and Snomax, (which contains P. syringae) that can be found around the proximity of the Texas Panhandle. By using the Cryogenic Refrigeration Applied Freezing Test (CRAFT) system, we estimated immersion freezing efficiency (i.e., ice nucleation activity scaled to a unit of mass) of each sample at the temperatures greater than -30°C. We have observed that not all gram-negative bacteria has high immersion freezing activity, but the few do have a warmer temperature onset (>-20 °C) than the cellulose used. For those that did not exhibit substantial freezing efficiencies, they had similar freezing properties as the broth, in which the bacteria were incubated, as well as the cellulose materials examined. These observations suggest the presence and potential importance of bacterial cellulose in the atmospheric ice nucleation. From here, we need to conduct more in-depth investigation in the effects of a wider variety of atmospherically relevant biological aerosols to get a better understanding of the effects of said aerosols on overall aerosol-cloud interactions. Acknowledgments: K. Cory would like to acknowledge NSF-EAPSI and JSPS Summer Program for the travel fellowship support. N. Hiranuma acknowledges financial aids by the Higher Education Assistance Fund (HEAF), WTAMU Office of Graduate School and Killgore Research Center.