Oxidation of atmospheric organic particulate matter
EMSL Project ID
17098
Abstract
Organic particulate matter is abundant throughout the atmosphere. These organic particles may contribute significantly to the radiative forcing, thus, changing the Earth's climate. Additionally, they may act as cloud condensation nuclei (CCN) and ice nuclei (IN), thereby, influencing the global radiation budget by cloud modification. Organic particulate matter is prone to oxidation by atmospheric trace gases such as NO3. Recent research has shown that organic particulate matter can be significantly modified by oxidation processes. The particle composition and its surface properties such as hygroscopicity may be altered, which directly effect its ability to act as CCN or IN. Also related, previous researchers have shown that OH-initiated oxidation of alkane surfaces leads to rapid volatilization and these same researchers concluded that volatilization by OH is at least as efficient as wet deposition as a removal process for aliphatic particulates. It is not known if this is also the case for NO3-initiated oxidation of the organic surface. Organic self assembled monolayers such as octadecanethiol (C-18 alkane) on gold serve as a proxy for the organic particulate matter. Objectives: Determination of the surface products from the reaction of NO3 with the organic monolayer, ODT, in the presence of O2. Also determine if the surface is rapidly volatized by the NO3 radicals. The surface products are studied as function of NO3 concentration, which reflects typical atmospherically observed concentrations and exposure times of the particles.
Approach : Gold plates coated with octadecanethiol are exposed to controlled amounts of NO3 which reflect atmospherically relevant exposure times using a chemical ionization mass spectrometer. These NO3 exposed OTD coated gold samples will then be investigated using the time of flight secondary ion mass spectrometer (TOF-SIMS) and Environmental Scanning Electron Microscopy.
Project Details
Project type
Exploratory Research
Start Date
2005-12-27
End Date
2007-01-08
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members