D. Bruce Harris

Effects of engine speed and accessory load on idling emissions from heavy-duty diesel truck engines.

Abstract A nontrivial portion of heavy-duty vehicle emissions of NOx and particulate matter (PM) occurs during idling. Regulators and the environmental community are interested in curtailing truck idling emissions, but current emissions models do not characterize them accurately, and little quantitative data exist to evaluate the relative effectiveness of various policies. The objectives of this study were to quantify the effect of accessory loading and engine speed on idling emissions from a properly functioning, modern, heavy-duty diesel truck and to compare these results with data from earlier model year vehicles. It was found that emissions during idling varied greatly as a function of engine model year, engine speed, and accessory load conditions. For the 1999 model year Class 8 truck tested, raising the engine speed from 600 to 1050 rpm and turning on the air conditioning resulted in a 2.5-fold increase in NOx emissions in grams per hour, a 2-fold increase in CO2 emissions, and a 5-fold increase in CO emissions while idling. On a grams per gallon fuel basis, NOx emissions while idling were approximately twice as high as those at 55 mph. The CO2 emissions at the two conditions were closer. The NOx emissions from the 1999 truck while idling with air conditioning running were slightly more than those of two 1990 model year trucks under equivalent conditions, and the hydrocarbon (HC) and CO emissions were significantly lower. It was found that the NOx emissions used in the California Air Resources Board’s (CARB) EMFAC2000 and the U.S. Environmental Protection Agency’s (EPA) MOBILE5b emissions inventory models were lower than those measured in all of the idling conditions tested on the 1999 truck.

Responses of cultured human airway epithelial cells treated with diesel exhaust extracts will vary with the engine load.

Epidemiologic evidence suggests that increased morbidity and mortality are associated with the concentrations of ambient air particulate matter (PM). Many sources contribute to the particulate fraction of ambient air pollution, including diesel exhaust particulates (DEP). Diesel exhaust also contributes gas-phase pollutants to the atmosphere, and gaseous copollutants may influence the toxicity of PM. The composition of diesel exhaust varies greatly depending on the engine load conditions as well as other factors. To determine whether different diesel exhaust composition can affect lung cell resposes, the effects of of diesel exhaust extracts derived from different engine loads were examined on normal human bronchial epithelial cells (NHBE) in vitro. Diesel exhaust was collected into chilled impingers containing phosphate-buffered saline (PBS). Cultured NHBE cells were treated with 0 to 500 microg/well extract from approximately 0% engine load (termed low load or LL) or extract from approximately 75% engine load (termed high load or HL) for 24 h. The HL extract was cytotoxic at 500 microg compared to controls as measured by (51)Cr release. Production of the neutrophil chemotaxin interleukin 8 (IL-8) was decreased 4.7-fold in cells treated with 500 microg LL extract, whereas cells treated with 500 microg HL extract showed a 2.4-fold increase in IL-8 release. Production of the inflammatory and immune system mediator prostaglandin E(2) (PGE(2)) was increased up to 2.5-fold in cells treated with HL extract, but unchanged with other treatments. Melittin stimulation of cells showed that the LL extract had an inhibitory effect on PGE(2) release at 500 microg. Differences in carbonyl content of the extracts were found by high performance liquid chromatography/mass spectroscopy HPLC/MS, with the HL extract having more intermediate size carbonyls (i.e. with six to nine carbons). The data suggest that the response of NHBE cells to treatment with diesel exhaust will vary depending on the constituent components of the exhaust.

Open-Path Tunable Diode Laser Absorption Spectroscopy for Acquisition of Fugitive Emission Flux Data

Abstract Air pollutant emission from unconfined sources is an increasingly important environmental issue. The U.S. Environmental Protection Agency (EPA) has developed a ground-based optical remote-sensing method that enables direct measurement of fugitive emission flux from large area sources. Open-path Fourier transform infrared spectroscopy (OP–FTIR) has been the primary technique for acquisition of pollutant concentration data used in this emission measurement method. For a number of environmentally important compounds, such as ammonia and methane, open-path tunable diode laser absorption spectroscopy (OP–TDLAS) is shown to be a viable alternative to Fourier transform spectroscopy for pollutant concentration measurements. Near-IR diode laser spectroscopy systems offer significant operational and cost advantages over Fourier transform instruments enabling more efficient implementation of the measurement strategy. This article reviews the EPA’s fugitive emission measurement method and describes its multipath tunable diode laser instrument. Validation testing of the system is discussed. OP-TDLAS versus OPFTIR correlation testing results for ammonia (R 2 = 0.980) and methane (R 2 = 0.991) are reported. Two example applications of tunable diode laser-based fugitive emission measurements are presented.

Comparison of the particle size distribution of heavy-duty diesel exhaust using a dilution tailpipe sampler and an in-plume sampler during on-road operation.

ABSTRACT Originally constructed to develop gaseous emission factors for heavy-duty diesel trucks, the U.S. Environmental Protection Agencys (EPA) On-Road Diesel Emissions Characterization Facility has been modified to incorporate particle measurement instrumentation. An electrical low-pressure impactor designed to continuously measure and record size distribution data was used to monitor the particle size distribution of heavy-duty diesel truck exhaust. For this study, which involved a high-mileage (900,000 mi) truck running at full load, samples were collected by two different methods. One sample was obtained directly from the exhaust stack using an adaptation of the University of Minnesotas air-ejector-based mini-dilution sampler. The second sample was pulled from the plume just above the enclosed trailer, at a point ~11 m from the exhaust discharge. Typical dilution ratios of about 300:1 were obtained for both the dilution and plume sampling systems. Hundreds of particle size distributions were obtained at each sampling location. These were compared both selectively and cumulatively to evaluate the performance of the dilution system in simulating real-world exhaust plumes. The data show that, in its current residence-time configuration, the dilution system imposes a statistically significant bias toward smaller particles, with substantially more nanoparticles being collected than from the plume sample.

On-Road Facility to Measure and Characterize Emissions from Heavy-Duty Diesel Vehicles

Abstract In response to lingering concerns about the utility of dynamometer data for mobile source emissions modeling, the U.S. Environmental Protection Agency (EPA) has constructed an on-road test facility to characterize the real-world emissions of heavy-duty trucks. The facility was designed to effectively demonstrate the full range of vehicle operation and to measure the emissions produced. Since it began operation, the facility has been continuously upgraded to incorporate state-of-the-art technology. Its potential uses include collecting modal emissions data, validating dynamometer test parameters and results, and demonstrating new emission control technologies.

Assessing Indoor Air Pollution Exposure and Lung Cancer Risk in Xuan Wei, China

This report presents the risk-assessment-related aspects of a multidisciplinary study of indoor coal smoke pollution and lung cancer in Xuan Wei County, Yunnan Province, China. Xuan Wei presents a unique natural experiment in environmental carcinogenesis because lung cancer mortality rates and indoor pollution exposures vary widely within the County. Current evidence links lung cancer with domestic burning of “smoky coal,” as opposed to “smokeless coal” and wood. Efforts to determine the most carcinogenic components of smoky coal pollution are in progress, as are efforts to develop a quantitative relationship of pollution dose with lung cancer response in Xuan Wei. Some available evidence suggests that the composition of indoor pollution does not vary greatly throughout Xuan Wei, and thus that lung cancer risk is a function of overall pollution exposure. Other evidence suggests that different Xuan Wei fuels exhibit different carcinogenic potencies. On-site and laboratory studies are being conducted to differentiate between these possibilities.

Comparison of an Innovative Nonlinear Algorithm to Classical Least-Squares for Analyzing Open-Path Fourier Transform Infrared Spectra Collected at a Concentrated Swine Production Facility:

Open-path Fourier transform infrared (OP/FT-IR) spectrometry was used to measure the concentrations of ammonia, methane, and other atmospheric gases at an integrated swine production facility. The concentration-pathlength products of the target gases at this site often exceeded the linear dynamic range of the OP/FT-IR spectrometer. To minimize the effect of this nonlinearity on the accuracy of the reported concentrations, a piecewise, linear classical least-squares (CLS) analysis method, which used a calibration set containing multiple reference spectra for each target gas at concentration-pathlength products that encompassed those found in the field spectra, was used to predict the path-averaged concentrations of the target gases. The predicted concentrations reported by this piecewise, linear CLS method were compared to those predicted by a conventional linear CLS method, which used a calibration set consisting of only one reference spectrum at a single concentration-pathlength product for each target gas, and an innovative nonlinear algorithm (NLA), which performs an iterative fit of the convolved spectral line data from the high-resolution transmission molecular absorption (HITRAN) database to the single-beam field spectra. The conventional, linear CLS method generally under-reported the target gas concentrations relative to those predicted by the piecewise, linear CLS method when the field spectra exhibited concentration-pathlength products larger than those of the reference spectra in the single-level calibration set. In extreme cases, for example, during measurements of methane along the waste lagoon, the concentrations predicted by the conventional CLS methods were more than 30% lower than those predicted by the piecewise, linear CLS method. In contrast, the concentrations of methane predicted by the NLA were, on average, within 4% of those predicted by the piecewise, linear CLS method. For ammonia, however, the concentrations predicted by the NLA were slightly higher than those predicted by the piecewise, linear CLS method at the lower range of observed concentration-pathlength products and slightly lower than those predicted by the piecewise, linear CLS method at the upper range of concentration-pathlength products. The NLA also consistently predicted higher concentrations of nitrous oxide and carbon dioxide relative to that predicted by the piecewise, linear CLS method. Differences in the background spectra and spectral ranges over which the analyses were conducted apparently did not contribute to the differences in the path-averaged concentrations predicted by these two analysis methods.

Ammonia Emissions from a U.S. Broiler House—Comparison of Concurrent Measurements Using Three Different Technologies

Abstract There is a need for robust and accurate techniques for the measurement of ammonia (NH3) and other atmospheric pollutant emissions from poultry production facilities. Reasonable estimates of NH3 emission rate (ER) from poultry facilities are needed to guide discussions about the industry’s impact on local and regional air quality. The design of these facilities features numerous emission points and results in emission characteristics of relatively low concentrations and exhaust flow rates that vary diurnally, seasonally, and with bird age over a considerable range. These factors combine to render conventional emissions monitoring approaches difficult to apply. Access to these facilities is also often restricted for biosecurity reasons. The three objectives of this study were (1) to compare three methods for measuring exhaust NH3 concentrations and thus ERs, (2) to compare ventilation rates using in situ measured fan characteristics versus using manufacturer sourced fan curves, and (3) to examine limitations of the alternative measurement technologies. In this study, two open-path monitoring systems operating outside of the buildings were compared with a portable monitoring system sampling upstream of a primary exhaust fan. The position of the open-path systems relative to the exhaust fans, measurement strategy adopted, and weather conditions significantly influenced the quality of data collected when compared with the internally located, portable monitoring system. Calculation of exhaust airflow from the facility had a large effect on calculated emissions and assuming that the installed fans performed as per published performance characteristics potentially overestimated emissions by 13.6–26.8%. The open-path measurement systems showed promise for being able to obtain ER measurements with minimal access to the house, although the availability of individual fan characteristics markedly improved the calculated ER accuracy. However, substantial operator skill and experience and favorable weather conditions were required to obtain good quality results.

An electrostatic precipitator backup filter for sampling systems

Abstract An alternative technique for filtering the aerosol effluent from particle sampling systems has been developed. A two-stage electrostatic precipitation system was designed to collect with high efficiency the paniculate material in a gas stream. The principal advantage of an electrostatic precipitator over conventional glass fiber backup filters is the ability to sample for long times without encountering filter pluggage or an excessive pressure differential across the system. Tests of a prototype electrostatic precipitator backup indicate collection efficiency for submicrometer diameter particles of 97 to greater than 99%.