Method development, speciated measurements and culculated reactivities of benzine, toluene, ethylbenzene and xylenes from vehicle exhaust
Mathematical modeling of ambient air photochemistry requires comprehensive speciation of hydrocarbons from mobile source emission. The objective of this study is to develop a simple and reliable method for analyzing tailpipe emission focusing on benzene, toluene, ethylbenzene and xylenes (BTEX)....
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| Format: | Thesis |
| Language: | English English |
| Published: |
2001
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/9213/1/FSAS_2001_10_A.pdf |
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| Summary: | Mathematical modeling of ambient air photochemistry requires comprehensive
speciation of hydrocarbons from mobile source emission. The objective of this study is
to develop a simple and reliable method for analyzing tailpipe emission focusing on
benzene, toluene, ethylbenzene and xylenes (BTEX). The method consists of sampling,
qualitative analysis and quantitative analysis. The samples were collected in Tedlar bags
at cold start and hot start conditions and were injected manually using a gas-tight syringe
into Gas Chromatograph-Mass Spectrometer (GC-MS) operated on Electron Impact
Ionization (EI) mode.
The method developed has demonstrated ability to produce rapid and reliable
separations of exhaust hydrocarbons. An approximate of 50 hydrocarbon compounds
were identified in the exhaust ranging from C₄ to C₁₂. It was found difficult to analyze C₁ to some of the C₄ hydrocarbons without the required accessories for volatile organic
gases analysis.
The emission rate of BTEX was emphasized because of its potential
carcinogenicity and toxicity. High concentration of BTEX was observed during cold
start and hot start. The mean concentrations of BTEX at cold start were as follows:
benzene (55.4 ppm), toluene (184.7 ppm), ethylbenzene (50.2 ppm), m-xylene (143.9
ppm), p-xylene (59.0 ppm) and o-xylene (65.4 ppm). The mean concentrations ofBTEX
at hot start were as follows: benzene (82.4 ppm), toluene (198.3 ppm), ethylbenzene
(40.0 ppm), m-xylene (184.0 ppm), p-xylene (62.1 ppm) and o-xylene (50.3 ppm).
The concentrations of BTEX in weighted percentages for all cars were fairly
constant. The weighted percentages concentration was used to estimate the
photochemical ozone reactivity by applying the Maximum Incremental Reactivity (MIR)
factors to the concentrations. The ozone forming potential as a result ofBTEX emission
from vehicle exhaust were estimated as follows: 3.07 g O₃/g benzene, 74.64 g O₃/g
toluene, 13.0 g 0₃/ g ethylbenzene, 145.8 g O₃/g m- and p-xylene, and 50.97 g O₃/g 0-
xylene. The results suggested that BTEX emitted from the vehicle exhaust increases the
formation of photochemical ozone in the atmosphere significantly. |
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