Levitt, Nicholas Paul (2007-05). Heterogeneous organic acid uptake on soot surfaces. Master's Thesis. | Thesis individual record

Atmospheric particulates have been known to act as cloud condensation nuclei
(CCN) and therefore their presence can indirectly affect important processes such as
global radiation balance through cloud formation. Soot particles are well known to be
atmospheric constituents, but the hydrophobic nature of fresh soot likely prohibits them
from encouraging cloud development. Soot aged through contact with oxygenated
organic compounds may become hydrophilic enough to promote water uptake. In this
study I have observed the interaction between a number of carboxylic acids and soot from
different fuel sources and formation mechanisms. A low pressure fast flow reactor was
used to control the contact between the solid phase soot and gas phase organics, while
chemical ionization-mass spectrometry was utilized to monitor concentrations of gas
phase organics. Most acids irreversibly deposited on the soot surfaces, and the uptake
coefficient was measured in the wide range of 9.0 x 10-4 to 1.0 x 10-1. The Brunauer,
Emmett, and Teller (BET) surface areas of the soots were measured and the soot bulk and
surface chemical compositions were investigated with Fourier transform infrared (FTIR)
spectroscopy and attenuated total reflection (ATR) spectroscopy to help explain
differences in uptake. By comparing the mono and dicarboxylic acids and the
information gathered from soot physiochemical properties I have discussed possible
uptake mechanisms.

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