Multicomponent Remote Sensing of Vehicle Exhaust by Dispersive Absorption Spectroscopy. 2. Direct On-Road Ammonia Measurements

Abstract

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.

Effect of low-sulfur fuels upon NH3 and N2O emission during operation of commercial three-way catalytic converters

“…In 1983, Pierson et al [4] reported 1.3 mg of NH 3 /km. In 1988, Fraser et al [5] stated that the ammonia emission was 60 mg/km, and in 2001, Baum et al [6] reported that it reached 94 mg/ km. As a result of that large rate of increase, the NH 3 factor published by US-EPA [7] to help predict emissions by gasoline cars was exceeded already in 1999.…”

Amônia (NH3) atmosférica: fontes, transformação, sorvedouros e métodos de análise

“…O sistema de medida respondeu proporcionalmente para a concentração de amônia na fase gasosa e tempo de pré-concentração. Amônia foi também determinada na exaustão de motores de veículos através de um sensor eletroquímico 114 , que também mediu as concentrações de CO 2 , CO, hidrocarbonetos, NO e outros poluentes emitidos na exaustão. O polímero polianilina foi sintetizado e dopado com ácido acrílico, para ser usado como um sensor de amônia gasosa numa ampla faixa de concentrações (1-600 ppm) 115 .…”

Lubricant pyrolysis during sintering of powder metallurgy compacts

“…[9,10,11] The measurement apparatus is calibrated and evaluated by connecting the sample cell to a gas manifold system. Synthetic mixtures (carbon dioxide, CO 2 , carbon monoxide, CO, and ammonia, NH 3 ) of known concentration are prepared by blending certified gases using mass flow controllers.…”