Darrell W. Joseph

A re-examination of ambient air ozone monitor interferences.

Abstract Attaining the National Ambient Air Quality Standard (NAAQS) for ozone (O3) could cost billions of dollars nationwide. Attainment of the NAAQS is judged on O3 measurements made by the Federal Reference Method (FRM), ethylene chemiluminescence, or a Federal Equivalent Method (FEM), predominantly ultraviolet (UV) absorption. Starting in the 1980s, FRM monitors were replaced by FEMs so that today virtually all monitoring in the United States uses the UV methodology. This report summarizes a laboratory and collocated ambient air monitoring study of interferences in O3 monitors. Potential interferences examined in the laboratory included water vapor, mercury, o-nitrophenol, naphthalene, p-tolualdehyde, and mixed reaction products from smog chamber simulations of urban atmospheric photochemistry. UV absorption O3 monitors modified for humidity equilibration were also collocated with UV FEM O3 monitors at six sites in Houston, TX, during the 2007 summer O3 season. The results suggest that humidity and interfering species can positively bias (overestimate) O3 measured by FEM monitors used to determine compliance with the O3 standards. The results also suggest that humidity equilibration can mitigate this bias.

An investigation of the ozone plume from a small city

Experiments are reported that were conducted during a major study of long range O/sub 3/ transport in urban plumes and high pressure weather systems. The focus of the study was to determine whether smaller cities contribute measurably to downwind O/sub 3/ concentrations, and to investigate the issue, an instrumented aircraft was used to perform upwind and downwind traverses in the vicinity of a large and a small city on several different days. It was concluded that under conditions conducive to photochemical O/sub 3/ formation, emissions from moderate size cities (populations of approximately 100,000) lead to a definable O/sub 3/ plume and can contribute measureably to the downwind O/sub 3/ burden. (JMT)

Extractive sampling and optical remote sensing of F100 aircraft engine emissions.

Abstract The Strategic Environmental Research and Development Program (SERDP) has initiated several programs to develop and evaluate techniques to characterize emissions from military aircraft to meet increasingly stringent regulatory requirements. This paper describes the results of a recent field study using extractive and optical remote sensing (ORS) techniques to measure emissions from six F-15 fighter aircraft. Testing was performed between November 14 and 16, 2006 on the trim-pad facility at Tyndall Air Force Base in Panama City, FL. Measurements were made on eight different F100 engines, and the engines were tested on-wing of in-use aircraft. A total of 39 test runs were performed at engine power levels that ranged from idle to military power. The approach adopted for these tests involved extractive sampling with collocated ORS measurements at a distance of approximately 20–25 nozzle diameters downstream of the engine exit plane. The emission indices calculated for carbon dioxide, carbon monoxide, nitric oxide, and several volatile organic compounds showed very good agreement when comparing the extractive and ORS sampling methods.

Size characterization of sulfuric acid aerosol emissions

In the course of a vehicle dynamometer study of sulfur emissions from an automobile equipped with oxidation catalysts, aerosol size distribution measurements were made while the exhaust was rapidly mixed with 10 parts of filtered air in a dilution tube. Results obtained with an electrical aerosol analyzer show that, under these dilution conditions, the sulfuric acid aerosols are consistently smaller than 0.3 ..mu..m in diameter. The distribution of aerosol volume (or mass) is slightly bimodal with maxima near 0.03 and 0.09 ..mu..m particle diameters. When a light-scattering effect is computed from theory using the observed particle size distributions good agreement is obtained between theory and measured light scattering. Within a reasonable margin of error, consistency is found between cascade impactor data, nephelometer light-scattering data, electrical analyzer data, and chemical analyses for sulfate.