Variability and Time of Day Dependence of Ozone Photochemistry in Western Wildfire Plumes.

Understanding the efficiency and variability of photochemical ozone (O) production from western wildfire plumes is important to accurately estimate their influence on North American air quality. A set of photochemical measurements were made from the NOAA Twin Otter research aircraft as a part of the Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) experiment. We use a zero-dimensional (0-D) box model to investigate the chemistry driving O production in modeled plumes.

Hygroscopic Characteristics of Alkylaminium Carboxylate Aerosols.

The hygroscopic growth factor (HGF) and cloud condensation nuclei (CCN) activity for a series of alkylaminium carboxylate aerosols have been measured using a hygroscopicity tandem differential mobility analyzer coupled to a condensation particle counter and a CCN counter. The particles, consisting of the mixtures of mono- (acetic, propanoic, p-toluic, and cis-pinonic acid) and dicarboxylic (oxalic, succinic, malic, adipic, and azelaic acid) acid with alkylamine (mono-, di-, and trimethylamines), represent those commonly found under diverse environmental conditions. The hygroscopicity parameter (κ) of the alkylaminium carboxylate aerosols was derived from the HGF and CCN results and theoretically calculated.

Volatility of atmospherically relevant alkylaminium carboxylate salts.

Heterogeneous neutralization reactions of ammonia and alkylamines with sulfuric acid play an important role in aerosol formation and particle growth. However, little is known about the physical and chemical properties of alkylaminium salts of organic acids. In this work we studied the thermal stability and volatility of alkylaminium carboxylate salts of short aliphatic alkylamines with monocarboxylic and dicarboxylic acids.

Role of interfacial water in the heterogeneous uptake of glyoxal by mixed glycine and ammonium sulfate aerosols.

This study focuses on the heterogeneous reactions of gas phase glyoxal with aerosols of glycine, the most abundant amino acid in atmospheric aerosols, as well as with a mixture of glycine and ammonium sulfate (AS) at a molar ratio of 1:100 (glycine-AS 1:100). Aerosols were exposed to varying relative humidity (RH) conditions in the presence of gas phase glyoxal for ∼1 h, followed by drying and efflorescence. The changes in size, chemical composition, and optical properties were consequently measured.

Changes in the optical properties of benzo[a]pyrene-coated aerosols upon heterogeneous reactions with NO2 and NO3.

Chemical reactions can alter the chemical, physical, and optical properties of aerosols. It has been postulated that nitration of aerosols can account for atmospheric absorbance over urban areas. To study this potentially important process, the change in optical properties of laboratory-generated benzo[a]pyrene (BaP)-coated aerosols following exposure to NO(2) and NO(3) was investigated at 355 nm and 532 nm by three aerosol analysis techniques.

Si-C-bound alkyl chains on oxide-free Si: towards versatile solution preparation of electronic transport quality monolayers.

We show that electronic transport quality alkyl chain mono-layers can be prepared from dilute solution, rather than from neat alkanes, and on Si (100) instead of (111) surfaces. High monolayer quality was deduced from XPS and from comparing current-voltage curves of Hg/alkyl/Si junctions with those for junctions with monolayers made from neat alkanes. XPS shows that limited surface oxidation does not harm the integrity of the monolayer.