You are here:
NEW DIRECTIONS: VOCS AND BIOSPHERE-ATMOSPHERE FEEDBACKS
Citation:
Fuentes, J. D., B. P. Hayden, M. Garstang, M. Lerdau, D. Fitzjarrald, D. D. Baldocchi, R. K. Monson, B. Lamb, AND C D. Geron*. NEW DIRECTIONS: VOCS AND BIOSPHERE-ATMOSPHERE FEEDBACKS. ATMOSPHERIC ENVIRONMENT 35(1):189-91, (2001).
Description:
Shallcross and Monks [New Directions: a Role For Isoprene in Biosphere-Climate-Chemistry Feedbacks, Atmospheric Environment, Vol. 34 (2000) pp. 1659-1660] recently summarized the importance of biogenic isoprene in a biosphere-atmosphere system under constant change. In this article, we expand this synthesis to include the biosphere feedbacks between plants that produce volatile organic compounds (VOCs) and the overlying atmosphere.
Plants produce a wide range of hydrocarbons including isoprene, terpenes, hemiterpenes, oxygenated species, and cuticular waxes. At the global scale, it its estimated that vegetation emits 1.2 X 10 to the 15th power g C per year, an amount equivalent to global methane (CH4) emissions.
There has been little direct experimental research on how global environmental change can affect emissions of phytogenic hydrocarbons. A broad-based research program is needed because VOCs rapidly react with hydroxyl radical (OH), ozone (O3), and nitrate (NO3). Such reactions lead to the formation of secondary chemical species (e.g., formaldehyde, peroxy radicals, carbonyl compounds, etc.) That can enhance O3 and other oxidant levels in locales rich in nitrogen oxides. The reaction of VOCs and OH can lead to enhanced CH4 levels, as OH is the major atmospheric sink for CH4. Poisson and co-workers [Journal of Atmospheric Chemistry, Vol. 36, (2000) pp. 157-230] estimated that VOC emissions have the global effect of incresing the lifetime of CH4 by 15% and enhancing background O3 levels by 18%. Once reacted, terpene compounds can also generate carbonaceous aerosols whose impacts may include feedback mechanisms in the Earth radiation balance. Finally, VOCs constitute a source of atmospheric carbon and can thus play key functions in the global carbon budget and cycling.