Dynamic accumulation chamber methods have been extensively used to estimate the total output of CO2released from active volcanic area. In order to asses the performance and reliability of a closed dynamicsystem several tests were carried out with different soil permeabilities and soil CO2 fluxes. A special devicewas used to create a constant one-dimensional CO2 flux through a soil column with a known permeability.Three permeabilities were investigated, ranging between 3.6×10−2 and 3.5×10 μm2, as were several CO2fluxes (ranging between 1.1×10−6 and 6.3×10−5 kg m−2 s−1). The results highlight that the accuracy of soilCO2 flux measurements strictly depends on the soil gas permeability and the soil CO2 flux regimen. Generallychamber measurements underestimate CO2 fluxes at low soil permeability and low soil CO2 fluxes, whereasappreciable overestimations occur for high permeability soil, especially for high soil CO2 fluxes. Other testscarried out with different settings for the measurement device, such as the chamber volume and the flux ofthe pump used to recirculate air through the chamber and the gas analyzer (recirculation flux), revealed astrong dependence of the closed dynamic chamber measurements on the recirculation flux. Lowrecirculation fluxes (0.2–0.4 l min−1) decreased the performance of the measurement system, causingunderestimations of the actual soil CO2 flux, whereas higher values (0.6–1.0 l min−1) resulted inoverestimations, especially for elevated soil CO2 fluxes. An empirical equation was deduced to allowaccumulation chamber fluxes to be calculated very accurately based on soil gas permeabilities measured inthe field.
|Numero di pagine||7|
|Stato di pubblicazione||Published - 2009|
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