Date of Award

Spring 1-1-2014

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry & Biochemistry

First Advisor

Margaret A. Tolbert

Second Advisor

Raina Gough

Third Advisor

Veronica Bierbaum

Abstract

Mineral dust particles are efficient ice nuclei (IN). NX illite, a new atmospheric dust surrogate, has been suggested to better represent atmospheric dust. Here Raman microscopy is used to examine the ice-nucleating efficiency of NX illite, NX illite coated with a five dicarboxylic acid mixture (M5), and pure M5. It was found that NX illite is a good IN, Sice=1.07 ± 0.01 at -47°C, with a slight Sice increase at lower temperatures, while pure M5 is a poor IN, Sice=1.30 ± 0.02 at -40°C, and relatively temperature independent. However, M5 shows different ice crystal mechanisms at low and high temperatures, suggesting depositional nucleation at low temperatures and immersion nucleation at high temperatures. In addition, 1:1 NX illite:M5 w/w is the threshold composition for hindering NX Illite's ice-nucleating ability. Understanding laboratory surrogates of atmospheric dust will lead to a more complete understanding of ice cloud formation and their effect on climate.

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