Introduction to Production,Transport, and Emission of TraceGases from the Vadose Zoneto the Atmosphere

摘要

Rising concerns about global warming as a consequence of increased anthropogenicgreenhouse gas emissions have markedly strengthened scientific, political, and evenpublic interest in issues surrounding human-induced climate change. Th is has resultedin fundamental economic and ecologic debates focusing on greenhouse gas mitigationstrategies. Besides H2O vapor, three major trace gases are primary contributors to thegreenhouse eff ect: CO_2, N_2O, and CH_4 (Intergovernmental Panel on Climate Change,2007). Such gases occur naturally in the atmosphere and are fundamental for life on Earth.With the onset of the industrial era, however, human activities, e.g., intensifi cation ofand changes in land use, industrial production, and burning of fossil fuel, among others,have resulted in the current atmospheric concentration of greenhouse gases signifi cantlyexceeding historical levels. In comparison to N_2O and CH_4, most of the CO_2 is emitted byfossil fuel burning. Nevertheless, biogenic CO_2 sources contribute about 17.3% to the totalgreenhouse gas emissions, whereas the overall emissions of N_2O and CH_4 contribute 7.9and 14.3%, respectively (Intergovernmental Panel on Climate Change, 2007). AlthoughN_2O and CH_4 represent a small fraction of the total mass of atmospheric greenhousegases, they are now receiving considerable attention because of their large global warmingpotentials of about 300 and 25 times that of CO_2, respectively (Intergovernmental Panelon Climate Change, 2007).