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There are many sources of variability when sampling motor vehicle emissions, including intermittant losses to “wetted” sampling system surfaces if water condensation occurs and thermal decomposition if sampling system surfaces get excessively hot. The risk of losses varies during typical transient speed emissions tests and depends upon many variables such as temperature, pressure, exhaust dilution ratio, dilution air humidity, fuel composition, and emissions composition. Procedures are described for injection of known concentrations of compounds of interest into transient motor vehicle exhaust for the purpose of characterizing losses between the vehicle tailpipe and emissions analyzer.

Combustion of organic motor vehicle fuels produces carbon dioxide and water (H2O) vapor (and also products of incomplete combustion, e.g. hydrocarbons and carbon monoxide, at lower concentrations). The Constant Volume Sampling (CVS) system, commonly used to condition auto exhaust for sampling and analysis, provides for controlled ambient air dilution of the engine exhaust. Water condensation can be a problem during CVS system sample conditioning, depending upon vehicle fuel composition and fuel economy, and diluent air humidity and exhaust/diluent ratio. This paper describes a “spreadsheet” procedure for detailed, second by second, determination of diluted exhaust dew point and the necessary CVS system flow rates to avoid H2O vapor condensation.

The characteristics of methanol and ethanol as highway motor vehicle fuels are contrasted with those of conventional gasolines and diesel fuels. The implications of the physical and chemical differences of these fuels for motor vehicle design and emissions are discussed. Potential material compatibility concerns, such as elastomer swelling and metal corrosion, and safety concerns, such as fire hazard, flame luminosity, and human toxicity are examined. A number of possible air quality impacts are examined including changes in ozone, carbon monoxide, oxides of nitrogen, particulate matter, toxic compounds (benzene, aldehydes, 1,3-butadiene), and global climate “greenhouse” gases (carbon dioxide, methane, nitrous oxide).

Apportionment of air pollution to sources requires knowledge of source emission strengths and/or chemical and physical characteristics. The literature is deficient in data useful for this purpose for heavy-duty motor vehicles, which can be important sources of air pollution in certain microenvironments. Emission factors are developed in this study for heavy-duty gasoline trucks using chassis dynamometer simulations of urban driving conditions. The sensitivity of the emissions to such considerations as the characteristics of the speed-time driving schedule, vehicle payload, and chassis configuration are examined. Emissions characterization includes total and individual hydrocarbons, aldehydes, carbon monoxide, oxides of nitrogen, total particulate matter, particulate organics, lead, bromine, chlorine, and the fraction of total particulate less than 2 μm. Preliminary comparisons of emissions obtained using transient engine and transient chassis test procedures are also reported.

A series of emissions tests were completed with 2 light duty diesel passenger cars, a Volkswagen and Oldsmobile, to examine the sensitivity of emission rates and composition to fuel. Four fuels including 3 petroleum distillates and an oil shale distillate were used in the program. The tests included 6 driving schedules. Determinations of gaseous emission rates, including total hydrocarbon, carbon monoxide, and oxides of nitrogen, and particulate emission rates were completed. Compositional characterization of the particulate matter included dichloromethane soluble organic fraction, benzo(a)pyrene, pyrene, nitropyrene, Ames TA-98 bioassay, and trace elements. Both gaseous and particulate mass emission rates were insensitive to the fuels examined in this program. The polynuclear aromatic hydrocarbon compounds associated with the particles varied between fuels, but were not well correlated with the fuel polynuclear aromatic hydrocarbon content.

Particulate emissions from 20 light-duty gasoline passenger cars and trucks were characterized using the Federal Test Procedure and Highway Fuel Economy Test driving cycles. Emission patterns were examined with 4 of the vehicles using three additional driving cycles, the hot start Federal Test Procedure, the Congested Urban Expressway and the New York City. The test fleet consisted of 4 noncatalyst vehicles operated with leaded gasoline and 16 catalyst-equipped vehicles operated with unleaded gasoline. The vehicles, obtained from local rental agencies, dealers, and residents, ranged in age from model year 1970 through 1981 and in mileage accumulation from about 300 to 81,000 miles. Particulate characterization included determination of total particulate emission rates, Ames bioassay of the dichloromethane soluble organic fraction, and analysis of the nitropyrene, pyrene, benzo-a-pyrene, and trace elements content.

The 1977 Clean Air Act Amendments, which call for broad study of motor vehicle particulate emissions, coupled with requirements for improved fuel economy, have greatly increased the interest and study of diesel powered motor vehicles. Analytical procedures are described which permit measurement of diesel organic emissions, including the particulate and gas phases, from carbon number 1 to carbon number 40. The partitioning of the emitted organics1 between the gas and particulate phases is examined with a variety of controllable sampling parameters. These parameters include variations in particulate sampling probe configurations and sampling rates, variable dilution ratios and corresponding temperatures, and filter media.

The advent of emission control technology has resulted in significant changes in both the total mass and detailed patterns of hydrocarbons emitted from automobiles. Emission rates of 56 hydrocarbons from 22 motor vehicles, including catalyst and noncatalyst configurations, were determined for the Federal Urban Driving Cycle. An increased relative abundance of methane is indicated for vehicles equipped with oxidation catalysts. In view of the photochemically non-reactive nature of methane, simple and economic procedures for determination of vehicle nonmethane hydrocarbon emission rates are evaluated. In general the procedures evaluated require independent total hydrocarbon and methane analysis, with the nonmethane hydrocarbon level calculated by difference. The procedures are evaluated by comparison of indicated nonmethane hydrocarbon emission rates with rates obtained by summation of individual compound rates determined by advanced gas chromatographic procedures.