Design and characterization of a two-stage human subject exposure chamber.

A human subject exposure chamber, designed to hold six to eight subjects, coupled to an approximately 30-m3 Teflon reaction bag was designed and built to provide exposures that mimic the production and photochemical oxidation of atmospheric pollutants resulting from the combustion of coal or wood from a stove. The combustion products are introduced into the Teflon bag under atmospheric conditions. Photochemical oxidation of this mixture is accomplished by exposure to tropospheric sun-like radiation from an array of ultraviolet and black lamps. The aerosol in the Teflon reaction bag is then transferred into the exposure room to maintain a constant, lower exposure level. Continuous and semicontinuous monitoring of the gas and particulate matter (PM) pollution in the exposure room and the reaction bag is accomplished using a suite of instruments. This suite of instruments allows for the measurement of the concentrations of total and nonvolatile PM, nitric oxide, nitrogen dioxide, carbon monoxide, carbon dioxide, and ozone. The concentration of the particles was monitored by an R&P tapered element oscillating microbalance monitor. The chemical composition of the PM and its morphological characterization is accomplished by collecting samples in filter packs and conducting ion chromatography, elemental X-ray fluorescence, and scanning electron microscopy analyses. The concentration and composition of emissions from combustion of wood and coal is described. The results of this study suggest that although the bulk compositions of particulate emissions from the combustion of coal or wood in a stove have many similarities, the wood smoke aerosol is photochemically reactive, whereas the coal smoke aerosol is not.

Semicontinuous PM2.5 and PM10 mass and composition measurements in Lindon, Utah, during winter 2007.

The U.S. Environmental Protection Agency is promoting the development and application of sampling methods for the semicontinuous determination of fine particulate matter (PM2.5, particles with an aerodynamic diameter <2.5 microm) mass and chemical composition. Data obtained with these methods will significantly improve the understanding of the primary sources, chemical conversion processes, and meteorological atmospheric processes that lead to observed PM2.5 concentrations and will aid in the understanding of the etiology of PM2.5-related health effects. During January and February 2007, several semicontinuous particulate matter (PM) monitoring systems were compared at the Utah State Lindon Air Quality Sampling site. Semicontinuous monitors included instruments to measure total PM2.5 mass (filter dynamic measurement system [FDMS] tapered element oscillating microbalance [TEOM], GRIMM), nonvolatile PM2.5 mass (TEOM), sulfate and nitrate (two PM2.5 and one PM10 [PM with an aerodynamic diameter <10 microm] ion-chromatographic-based samplers), and black carbon (aethalometer). PM10 semicontinuous mass measurements were made with GRIMM and TEOM instruments. These measurements were all made on a 1-hr average basis. Source apportionment analysis indicated that sources impacting the site were mainly urban sources and included mobile sources (gasoline and diesel) and residential burning of wood, with some elevated concentrations because of the effect of winter inversions. The FDMS TEOM and GRIMM instruments were in good agreement, but TEOM monitor measurements were low because of the presence of significant semi-volatile material. Semi-volatile mass was present dominantly in the PM2.5 mass.