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By NATCHAYA PINGINTHA MONIQUE Y. LECLERC JOHN P. BEASLEY Jr. GENGSHENG ZHANG CHUCKREE SENTHONG 《Tellus. Series B, Chemical and physical meteorology》2010,62(1):47-58
This paper uses a refined soil gradient method to estimate soil CO2 efflux. Six different models are used to determine the relative gas diffusion coefficient (ξ). A weighted harmonic averaging is used to estimate the soil CO2 diffusion coefficient, yielding a better estimate of soil CO2 efflux. The resulting soil CO2 efflux results are then compared to the soil CO2 efflux measured with a soil chamber. Depending on the choice of ξ model used, the estimated soil CO2 efflux using the gradient method reasonably approximates the efflux obtained using the soil chamber method. In addition, the estimated soil CO2 efflux obtained by this improved method is well described by an exponential function of soil temperature at a depth of 0.05 m with the temperature sensitivity ( Q 10 ) of 1.81 and a linear function of soil moisture at a depth of 0.12 m, in general agreement with previous findings. These results suggest that the gradient method is a practical cost-effective means to measure soil CO2 emissions. Results from the present study suggest that the gradient method can be used successfully to measure soil CO2 efflux provided that proper attention is paid to the judicious use of the proper diffusion coefficient. 相似文献
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J.-D. PARIS P. CIAIS P. NÉDÉLEC M. RAMONET B. D. BELAN M. YU. ARSHINOV G. S. GOLITSYN I. GRANBERG A. STOHL G. CAYEZ G. ATHIER F. BOUMARD J.-M. COUSIN 《Tellus. Series B, Chemical and physical meteorology》2008,60(4):551-568
Two airborne campaigns were carried out to measure the tropospheric concentrations and variability of CO2 , CO and O3 over Siberia. In order to quantify the influence of remote and regional natural and anthropogenic sources, we analysed a total of 52 vertical profiles of these species collected in April and September 2006, every ∼200 km and up to 7 km altitude. CO2 and CO concentrations were high in April 2006 (respectively 385–390 ppm CO2 and 160–200 ppb CO) compared to background values. CO concentrations up to 220 ppb were recorded above 3.5 km over eastern Siberia, with enhancements in 500–1000 m thick layers. The presence of CO enriched air masses resulted from a quick frontal uplift of a polluted air mass exposed to northern China anthropogenic emissions and to fire emissions in northern Mongolia. A dominant Asian origin for CO above 4 km (71.0%) contrasted with a dominant European origin below this altitude (70.9%) was deduced both from a transport model analysis, and from the contrasted ΔCO/ΔCO2 ratio vertical distribution. In September 2006, a significant O3 depletion (∼–30 ppb) was repeatedly observed in the boundary layer, as diagnosed from virtual potential temperature profiles and CO2 gradients, compared to the free troposphere aloft, suggestive of a strong O3 deposition over Siberian forests. 相似文献
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