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  • 1
    Electronic Resource
    Electronic Resource
    Measurements of carbon sequestration by long-term eddy covariance: methods and a critical evaluation of accuracy (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Global change biology 2 (1996), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: The turbulent exchanges of CO2 and water vapour between an aggrading deciduous forest in the north-eastern United States (Harvard Forest) and the atmosphere were measured from 1990 to 1994 using the eddy covariance technique. We present a detailed description of the methods used and a rigorous evaluation of the precision and accuracy of these measurements. We partition the sources of error into three categories: (1) uniform systematic errors are constant and independent of measurement conditions (2) selective systematic errors result when the accuracy of the exchange measurement varies as a function of the physical environment, and (3) sampling uncertainty results when summing an incomplete data set to calculate long-term exchange.Analysis of the surface energy budget indicates a uniform systematic error in the turbulent exchange measurements of -20 to 0%. A comparison of nocturnal eddy flux with chamber measurements indicates a selective systematic underestimation during calm (friction velocity 〈 0.17 m s−1) nocturnal periods. We describe an approach to correct for this error. The integrated carbon sequestration in 1994 was 2.1 t C ha−1 y−1 with a 90% confidence interval due to sampling uncertainty of ±0.3 t C ha−1 y−1 determined by Monte Carlo simulation. Sampling uncertainty may be reduced by estimating the flux as a function of the physical environment during periods when direct observations are unavailable, and by minimizing the length of intervals without flux data. These analyses lead us to place an overall uncertainty on the annual carbon sequestration in 1994 of -0.3 to +0.8 t C ha−1 y−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2486.1996.tb00070.x
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  • 2
    Electronic Resource
    Electronic Resource
    Surface ozone depletion in Arctic spring sustained by bromine reactions on aerosols (1992)
    [s.l.] : Nature Publishing Group
    Nature 359 (1992), S. 522-524 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The chemical cycling of inorganic bromine (Brx) in the troposphere is summarized in Fig. 1. The reaction of Br atoms with ozone, followed by the self-reaction of the BrO produced, represents a catalytic loss mechanism for ozone as Br is regenerated. Concentrations of Brx collected on filters during ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/359522a0
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  • 3
    Electronic Resource
    Electronic Resource
    Methane and nitrogen gases from rice fields of China — possible effects of microbiology, benthic fauna, fertilizer, and agricultural practice (1988)
    Springer
    Water, air & soil pollution 37 (1988), S. 149-155 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Estimation of release rates of CH4, N2O, and other trace gases from rice agriculture in China requires that details of microbiology, rice field benthic fauna, fertilizer use, and how farmers farm be understood. The potential importance of natural fertilizer can be estimated, based on published biogas generator efficiency in rural China, with the result that CH4 production from the fermentation of animal and human wastes prior to use as fertilizer may be comparable to that expected to be released from flooded rice fields. A review of agricultural practices in Anhui and Fujian Provinces indicates that marked seasonal and geographic variations in CH4 and other trace gas releases to the atmosphere from Chinese agricultural areas are expected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00226487
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