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Diffusion theory improves chamber‐based measurements of trace gas emissions
Author(s) -
Livingston Gerald P.,
Hutchinson Gordon L.,
Spartalian Kevork
Publication year - 2005
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2005gl024744
Subject(s) - diffusion , trace gas , environmental science , atmosphere (unit) , range (aeronautics) , trace (psycholinguistics) , porosity , flux (metallurgy) , soil science , mechanics , atmospheric sciences , materials science , meteorology , geology , physics , thermodynamics , geotechnical engineering , linguistics , philosophy , metallurgy , composite material
Chambers temporarily sealed to the soil surface are an important and for many purposes the only means of measuring trace gas emissions to the atmosphere. However, past interpretations of chamber data systematically underestimated actual emission rates in most applications because they ignored or poorly modeled the effect of the chamber on the gas exchange process. To address this issue, we introduce a time‐dependent diffusion model applicable to non‐steady‐state chamber observations and evaluate its performance, as well as that of previously published models, using concentration data simulated by an independent, 3‐dimensional numeric diffusion model. The results demonstrate that commonly cited past measurement practices underestimate emission rates 15% to 25% under most circumstances and that the error varies with chamber height, soil air‐filled porosity and flux model used to interpret the concentration data. In contrast, our model proved accurate and readily applicable over the entire range of soil and chamber dimensions evaluated.