Methodology and calibration for continuous measurements of biogeochemical trace gas and Osub2/sub concentrations from a 300-m tall tower in central Siberia

摘要

We present an integrated system for measuring atmosphericconcentrations of CO₂, O₂, CH₄, CO, and N₂O in centralSiberia. Our project aims to demonstrate the feasibility of establishinglong-term, continuous, high precision atmospheric measurements to elucidategreenhouse gas processes from a very remote, mid-continental borealenvironment. Air is sampled from five heights on a custom-built 300-m tower.Common features to all species' measurements include air intakes, an airdrying system, flushing procedures, and data processing methods. Calibrationstandards are shared among all five measured species by extending andoptimising a proven methodology for long-term O₂ calibration. Oursystem achieves the precision and accuracy requirements specified by theEuropean Union's "CarboEurope" and "ICOS" (Integrated Carbon ObservingSystem) programmes in the case of CO₂, O₂, and CH₄, while COand N₂O require some further improvements. It was found that it is notpossible to achieve these high precision measurements without skilledtechnical assistance on-site, primarily because of 2–3 month delays inaccess to data and diagnostic information. We present results on thestability of reference standards in high pressure cylinders. It was alsofound that some previous methods do not mitigate fractionation of O₂ ina sample airstream to a satisfactory level.