Intermediate-volatility organic compounds: a large source of secondary organic aerosol.

Secondary organic aerosol (SOA) is a major component of atmospheric fine particle mass. Intermediate-volatility organic compounds (IVOCs) have been proposed to be an important source of SOA. We present a comprehensive analysis of atmospheric IVOC concentrations and their SOA production using measurements made in Pasadena, California during the California at the Nexus of Air Quality and Climate Change (CalNex) study.

Vertically resolved measurements of nighttime radical reservoirs in Los Angeles and their contribution to the urban radical budget.

Photolabile nighttime radical reservoirs, such as nitrous acid (HONO) and nitryl chloride (ClNO(2)), contribute to the oxidizing potential of the atmosphere, particularly in early morning. We present the first vertically resolved measurements of ClNO(2), together with vertically resolved measurements of HONO. These measurements were acquired during the California Nexus (CalNex) campaign in the Los Angeles basin in spring 2010.

Organosulfates as tracers for secondary organic aerosol (SOA) formation from 2-methyl-3-buten-2-ol (MBO) in the atmosphere.

2-Methyl-3-buten-2-ol (MBO) is an important biogenic volatile organic compound (BVOC) emitted by pine trees and a potential precursor of atmospheric secondary organic aerosol (SOA) in forested regions. In the present study, hydroxyl radical (OH)-initiated oxidation of MBO was examined in smog chambers under varied initial nitric oxide (NO) and aerosol acidity levels. Results indicate measurable SOA from MBO under low-NO conditions.

Isocyanic acid in the atmosphere and its possible link to smoke-related health effects.

We measured isocyanic acid (HNCO) in laboratory biomass fires at levels up to 600 parts per billion by volume (ppbv), demonstrating that it has a significant source from pyrolysis/combustion of biomass. We also measured HNCO at mixing ratios up to 200 pptv (parts-per-trillion by volume) in ambient air in urban Los Angeles, CA, and in Boulder, CO, during the recent 2010 Fourmile Canyon fire. Further, our measurements of aqueous solubility show that HNCO is highly soluble, as it dissociates at physiological pH.

Source identification of reactive hydrocarbons and oxygenated VOCs in the summertime in Beijing.

It is important to identify the sources of reactive volatile organic compounds (VOCs) in Beijing for effective ground-level ozone abatement. In this paper, semihourly measurements of hydrocarbons and oxygenated VOCs (OVOCs) were taken at an urban site in Beijing in August2005. C2-C5 alkenes, isoprene, and C1-C3 aldehydes were determined as "key reactive species" by their OH loss rates.

Online volatile organic compound measurements using a newly developed proton-transfer ion-trap mass spectrometry instrument during New England Air Quality Study--Intercontinental Transport and Chemical Transformation 2004: performance, intercomparison, and compound identification.

We have used a newly developed proton-transfer ion-trap mass spectrometry (PIT-MS) instrument for online trace gas analysis of volatile organic compounds (VOCs) during the 2004 New England Air Quality Study-Intercontinental Transport and Chemical Transformation study. The PIT-MS instrument uses proton-transfer reactions with H3O+ ions to ionize VOCs, similarto a PTR-MS (proton-transfer reaction mass spectrometry) instrument but uses an ion trap mass spectrometer to analyze the product ions. The advantages of an ion trap are the improved identification of VOCs and a near 100% duty cycle.

Inter-comparison of laser photoacoustic spectroscopy and gas chromatography techniques for measurements of ethene in the atmosphere.

Laser photoacoustic spectroscopy (LPAS) is highly suitable for the detection of ethene in air due to the overlap between its strongest absorption lines and the wavelengths accessible by high-powered CO2 lasers. Here, we test the ability of LPAS to measure ethene in ambient air by comparing the measurements in urban air with those from a gas chromatography flame-ionization detection (GC-FID) instrument. Over the course of several days, we obtained quantitative agreement between the two measurements.

Temporal changes in U.S. benzene emissions inferred from atmospheric measurements.

The 1990 Clean Air Act Amendments required the United States Environmental Protection Agency (U.S. EPA) to enact stricter regulations aimed at reducing benzene emissions.

Validation of atmospheric VOC measurements by proton-transfer-reaction mass spectrometry using a gas-chromatographic preseparation method.

Proton-transfer-reaction mass spectrometry (PTR-MS) has emerged as a useful tool to study volatile organic compounds (VOCs) in the atmosphere. In PTR-MS, proton-transfer reactions with H30+ ions are used to ionize and measure VOCs in air with a high sensitivity and fast time response. Only the masses of the ionized VOCs and their fragments, if any, are determined, and these product ions are not unique indicators of VOC identities.