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| Titel |
A conjugated mess: measurements of benzene (C6H6), CH4, CO2, and H2O using a cavity ring-down spectrometer |
| VerfasserIn |
Derek Fleck, John Hoffnagle, Yonggang He |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250147456
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| Publikation (Nr.) |
 EGU/EGU2017-11622.pdf |
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| Zusammenfassung |
| Benzene is widely used carcinogenic chemical that ranks among the top 15 chemicals
produced in the world by volume. It is part of many industrial processes from solvents to
rubber and drug production and is also produced in petroleum refinement and use. OSHA and
European regulators have set a strict long-term exposure limit and short-term exposure limit
of 1ppm and 15ppm, respectively, to minimize hazards to a person’s health. With the recent
passing by the EPA of mandatory fence line monitoring of benzene at petroleum factories, it
is evident that a robust, continuous measurement of benzene is necessary. Conventional
measurements of benzene suffer from a high granularity (nearly 1 ppm), cumbersome sample
preparation/processing, or cross-sensitivities from other gas species. The aim of this
study is to show development of an analyzer using cavity ring-down spectrometry
(CRDS) to measure benzene, as well as all the main constituents of air that can
influence a measurement: H2O, CO2, and CH4. A measurement of benzene to an
uncertainty of 100 ppb in <5 minutes is currently attainable, with a future goal of making
this measurement in only ten seconds to 1 minute. Initial results show precisions
of CH4 at 0.5ppb, CO2 at 0.5ppm and H2O of 10ppm. Because of the relatively
IR-inactive C6H6 molecule, only broad features lying underneath the relatively sharp
signals of CH4, CO2, and H2O can be used to quantify benzene concentrations.
The stability of the CRDS analyzer allows us to look at structured changes in the
baseline due to benzene to get out a precise measurement, while rarely having to do a
zero-reference calibration. The analysis of these four species yields an instrument that
is not only viable for fence line monitoring of petroleum refineries, but one that
could also be used for local atmospheric monitoring of cities or even gas-stations. |
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