Hydrogen in the atmosphere: Observations above a forest canopy in a polluted environment

Long‐term in situ observations of atmospheric concentrations of molecular hydrogen were monitored every 24 minutes for three years (1996–1998) above Harvard Forest, Massachusetts, in concert with measurements of carbon monoxide and twelve other trace gases. A seasonal cycle with a spring maximum and...

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Bibliographic Details
Published in:Journal of Geophysical Research 2003-03, Vol.108 (D6), p.ACH10.1-n/a
Main Authors: Barnes, Diana H., Wofsy, Steven C., Fehlau, Brian P., Gottlieb, Elaine W., Elkins, James W., Dutton, Geoffrey S., Novelli, Paul C.
Format: Article
Language:English
Subjects:
Air pollution
Applied sciences
Atmospheric pollution
Automobiles
Automotive engines
Boundaries
Canopies
car exhaust
Carbon dioxide
Carbon monoxide
Chemical composition and interactions. Ionic interactions and processes
Earth, ocean, space
emissions
Emissions control
Equilibrium conditions
Exact sciences and technology
External geophysics
Fluctuation
Forests
Gases
Hydrogen
Meteorology
Pollutants physicochemistry study: properties, effects, reactions, transport and distribution
Pollution
troposphere
Uptakes
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Summary:Long‐term in situ observations of atmospheric concentrations of molecular hydrogen were monitored every 24 minutes for three years (1996–1998) above Harvard Forest, Massachusetts, in concert with measurements of carbon monoxide and twelve other trace gases. A seasonal cycle with a spring maximum and autumn minimum was observed. The diurnal cycle was characterized by a morning minimum and an afternoon maximum, reflecting the combined effects of uptake by soils and boundary height fluctuations. Enhancements of H2 concentrations in pollution events, concurrent with winds from the southwest, were typically 100–200 ppb above the background seasonal cycle. The mean molar ratio of H2 and CO (ΔH2/ΔCO) in pollution plumes was 0.396 ± 0.050 ppb/ppb. The results agree with expectations from the water‐gas equilibrium (CO + H2O ↔ CO2 + H2) for conditions in automobile engines and with car emission data. These observations suggest that automobiles are the major anthropogenic source of atmospheric hydrogen and that the ratio of ΔH2/ΔCO has changed little as emission controls have taken effect.
ISSN:0148-0227
2156-2202
DOI:10.1029/2001JD001199