Remote sensing was employed for the first time to measure NH3 levels in the exhaust of on-road light duty motor vehicles. The sensor also measured the concentration of CO2, CO, hydrocarbons, and NO, among other pollutants, in the emitted exhaust. Field measurements were conducted at a Los Angeles freeway on-ramp; vehicles traveled at cruise speeds between 20 and 25 m s(-1) (45-55 mi h(-1)). Mean fleet NH3 levels of 44.7 +/- 4.1 ppm were observed. These emissions exhibited a highly skewed distribution: 50.1% of the emitted NH3 was contributed by 10% of the sampled fleet. The pollutant distribution among high NH3 emitters is analyzed to identify the conditions that lead to three-way catalyst malfunction and, hence, NH3 formation. In contradiction with previous reports, we found that high NH3 emissions could not be attributed to vehicles running under rich air-fuel conditions. We estimate a mean fleet NH3 mass emission rate of 667 +/- 57 mg L(-1) (Er = 94 +/- 8 mg km(-1)). These findings could have significant implications on air quality in the South Coast Air Basin (SoCAB) of California, since they support the hypothesis that emissions from motor vehicles constitute a dominant regional source of NH3, between 20 and 27% of total daily emissions. As NH3 is the predominant atmospheric base, tropospheric levels play a key role in the buffering capacity of the atmosphere and, hence, the formation of fine aerosol. Our results could explain the ubiquitous distribution of ammonium fine particles observed during fall stagnation conditions in the SoCAB.

A remote sensor incorporating UV and IR spectrometers in conjunction with an innovative optical design is described. The instrument was used to noninvasively measure over 20 pollutants in the exhaust of 19 in-use vehicles powered by a range of fuelsreformulated Phase II gasoline, diesel, compressed natural gas, and methanol blended with 15% gasoline. CO2, CO, aldehydes, and aliphatic and speciated aromatic hydrocarbons were identified along with NO x , determined as the sum of NO, NO2; N2O and HONO were also measured, although their levels were typically below the instrument's detection limit. NH3 levels in vehicle exhaust are reported for the first time on a car-by-car basis. The exhaust from gasoline- and methanol-powered cars was found to contain elevated levels of NH3, in some cases over 1000 ppm, despite near stoichiometric air-to-fuel ratios, and were often significantly higher than corresponding NO levels. Catalyst efficiency is discussed as a function of NH3 and NO concentrations in the exhaust of vehicles operating “cold” and “hot”. In some of the tested vehicles, the three-way catalysts showed high reduction activity but poor selectivity resulting in the formation of NH3 and possibly other nitrogen-containing products other than N2. These observations could have significant implications on the formation of ammonium nitrate aerosol and on the acid-neutralizing capacity of urban air masses.

Recent data indicate that, in many countries, mobile sources are responsible for the largest portion of emissions of aldehydes, ketones and certain other air toxic pollutants. These air toxic pollutants along with methane are either carcinogenic or pose significant human health threat. These pollutants also add to global warming in a substantial way. This paper gives an overview of their properties, basic chemistry and conditions of formation in internal combustion engines. Again worldwide many countries are promoting alternative fuels to tackle the crisis of traditional fuel. But the impact of this movement toward alternative fuels with respect to toxic emissions has not been well studied. Therefore, in this paper the analysis on the effects of engine operation and fuelling parameters is also reviewed with specific references in gasoline, diesel, natural gas, liquefied petroleum gas, ethanol blended petrol and Biodiesel fuelled engines. This is accompanied by the review of the studies of the performance of exhaust catalytic converters with respect to aldehydes, ketones and methane. Additionally, aldehydes, ketones and methane detection and measurement methods are summarized and analyzed from the view of their applicability to exhaust gas analysis.

A new, miniaturized, noninvasive instrument for rapid acetylene analysis in breath gas is described. Acetylene is a blood-soluble gas and for many years its uptake rate during rebreathing and/or nonrebreathing tests has been used to calculate the volume of lung tissue as well as the flow rate of blood through the lungs. The instrument relies on dispersive UV absorption spectroscopy as its measurement principle and is employed in an extractive (side-stream) configuration. The analyzer afforded fast (276±43 ms, 0%–90%, at 2 L min−1 flow rates), interference-free detection of acetylene, with signal-to-noise ratios in excess of 50. Comparison tests with a mass spectrometer using calibration gas samples gave an excellent correlation {[C2H2]MS=0.999. [C2H2]UV, R2=1.000}, which validated the linearity and accuracy of the UV system. A similar level of correlation between these devices also was observed during human subject C2H2 uptake tests, with both instruments sampling a common extracted gas stream {[C2H2]UV=0.940. [C2H2]MS, R2=0.998}. These results indicate that a miniature, low-cost, rugged, ultraviolet spectrometer system measuring acetylene holds promise for human breath analysis in a clinical setting.

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