J. P. Johnson

Diesel Aerosol Sampling in the Atmosphere

The University of Minnesota Center for Diesel Research along with a research team including Caterpillar, Cummins, Carnegie Mellon University, West Virginia University (WVU), Paul Scherrer Institute in Switzerland, and Tampere University in Finland have performed measurements of Diesel exhaust particle size distributions under real-world dilution conditions. A mobile aerosol emission laboratory (MEL) equipped to measure particle size distributions, number concentrations, surface area concentrations, particle bound PAHs, as well as CO 2 and NO x concentrations in real time was built and will be described. The MEL was used to follow two different Cummins powered tractors, one with an older engine (L10) and one with a state-of-the-art engine (ISM), on rural highways and measure particles in their exhaust plumes. This paper will describe the goals and objectives of the study and will describe representative particle size distributions observed in roadway experiments with the truck powered by the ISM engine.

On-Road Exposure to Highway Aerosols. 1. Aerosol and Gas Measurements

On-road experiments were conducted to determine the sensitivities of rats to real-world aerosol. This article summarizes the on-road aerosol and gas measurements and provides background information for the companion paper on the rat exposures. Measurements were carried out over 10 days, 6 h/day, driving a route from Rochester to Buffalo. Aerosol instrumentation used in this study included two scanning mobility particle sizers (SMPS) to determine the aerosol size distribution from 10 to 300 nm, 2 stand-alone condensation particle counters to determine the total aerosol number concentration, and an electrical aerosol detector to determine the aerosol length concentration. A thermal denuder (TD) was used with one of the SMPS instruments to determine the size distribution of the non-volatile fraction. Filter samples were collected and analyzed for elemental carbon, and gas analyzers measured ambient levels of CO, CO2, and NO. Average daily total aerosol number concentration ranged from 200,000 to 560,000 particles/cm3. Past studies on urban highways have measured total number concentrations ranging between 104 and 106 particles/cm3. The average daily NO concentration ranged from 0.10 to 0.24 ppm and the corresponding CO2 concentration ranged from 400 to 420 ppm. The average daily geometric number mean particle size determined by the SMPS ranged from 15 to 20 nm. The TD reduced the average SMPS number concentration between 87 and 95% and the SMPS volume between 54 and 83%, suggesting that most of the particles consisted of volatile material. The TD also increased the geometric number mean diameter from 15 to 20 nm to 30 to 40 nm.

Impact of Ambient Temperatures and Driving Conditions on the Chemical Composition of Particulate Matter Emissions from Non-Smoking Gasoline-Powered Motor Vehicles

The detailed chemical composition of particulate matter emissions from four non-smoking gasoline powered motor vehicles were measured using three different driving conditions: a cold-cold start Unified Driving Cycle (UDC), a hot UDC, and a steady state cruise driving cycle. The cold-cold start UDC tests were performed with a cold-cold start temperature of 0°C, which is significantly lower than the 24°C cold start temperature widely used for motor vehicle testing. Each vehicle was operated over three cold-cold UDC cycles, three hot UDC cycles, and a steady state driving cycle comprised of 2 hours at 100 kilometers per hour (kph) plus 1 hour at 50 kph. Particulate matter emissions were characterized for elemental carbon (EC), organic carbon (OC), sulfate ions, nitrate ions, ammonium ions, and organic compounds using gas chromatography mass spectrometry (GCMS). Mass emissions rates for the test vehicles using both the hot UDC and steady state driving cycles ranged from < 0.1 to 1.3 mg km −1 , while the average cold-cold UDC cycle emissions ranged from 1.0 to 7.1 mg km −1 for the four vehicles. The cold-cold start UDC emissions averaged 5–30 times higher than the hot start UDC emissions. EC was an important contributor to the particulate matter emissions for the cold-cold start UDC emissions. Speciation of the organic compounds in the particulate matter emissions demonstrates differences in the composition of the organic aerosol emissions for the different driving cycles. The results of the present study demonstrate the important impact of cold-cold start temperature and driving conditions.

Driving down on-highway particulate emissions

It has been reported that particulate emissions from diesel vehicles could be associated with damaging human health, global warming and a reduction in air quality. These particles cover a very large size range, typically 3 to 10 000 nm. Filters in the vehicle exhaust systems can substantially reduce particulate emissions but until very recently it was not possible to directly characterise actual on-road emissions from a vehicle. This paper presents the first study of the effect of filter systems on the particulate emissions of a heavy-duty diesel vehicle during real-world driving. The presence of sulfur in the fuel and in the engine lubricant can lead to significant emissions of sulfate particles < 30 nm in size (nanoparticles). We have demonstrated that when using low sulfur fuel in combination with a uniquely formulated low sulfur lubricant and a suitable filter system that the particulate emissions of a heavy-duty vehicle were reduced to the levels already present in the ambient environment. PM EMISSIONS AND DIESEL PARTICULATE FILTER (DPF) TECHNOLOGY Diesel Particulate Matter (PM) consists primarily of carbonaceous soot and a Volatile Organic Fraction (VOF) composed mainly of hydrocarbons with lesser amounts of nitrate and sulfate species. It is becoming increasingly recognised that PM emissions from dieselpowered vehicles may have adverse environmental effects. For example, it was proposed that the elemental carbon fraction can increase global warming effects. In addition, the medical community is closely examining the effects of PM on human health as a function of particle size. Reports in scientific literature suggest that there is a link between environmental exposure to fine particles less than 2.5 m in size to adverse health effects. These studies elucidated a range of causal mechanisms but have not developed a quantitative understanding of their relative importance. Studies that are more recent investigated the hypothesis that ultrafine particles <100 nm in size are detrimental to human health. It has also been reported that the relationship between ultrafine particles and health may be at least partially due to the high efficiency of particle deposition in the respiratory tract for the very small particles (Alveolar deposition is highest for particles approximately 20 nm in size). Regulatory agencies such as the U.S. Environmental Protection Agency (EPA) have adopted mass-based air pollution regulations for particulate matter. Other metrics, such as particle number or surface area, may be more important in characterising the physical properties of aerosol related to health effects. Figure 1 illustrates relationships between combustion aerosol number, surface area and mass weighted size distributions. In this case the distribution typifies a diesel aerosol distribution. The shape of the aerosol size distribution from a spark ignition engine would be similar but with relatively less material in the accumulation mode region. 2006-01-0916 Driving Down On-Highway Particulate Emissions D. B. Kittelson, W. F. Watts and J. P. Johnson University of Minnesota, Department of Mechanical Engineering