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Abstract

Quasi-continuous, in-situ measurements of atmospheric CO₂, O-2/N-2, CH₄, CO, N₂O, and SF₆ have been performed since August 2005 at the tall tower station near Bialystok, in Eastern Poland, from five heights up to 300 m. Besides the in-situ measurements, flask samples are filled approximately weekly and measured at Max-Planck Institute for Biogeochemistry for the same species and, in addition, for H-2, Ar/N-2 and the stable isotopes C-13 and O-18 in CO₂. The in-situ measurement system was built based on commercially available analysers: a LiCor 7000 for CO₂, a Sable Systems " Oxzilla" FC-2 for O-2, and an Agilent 6890 gas chromatograph for CH₄, CO, N₂O and SF₆. The system was optimized to run continuously with very little maintenance and to fulfill the precision requirements of the CHIOTTO project. The O-2/N-2 measurements in particular required special attention in terms of technical setup and quality assurance. The evaluation of the performance after more than three years of operation gave overall satisfactory results, proving that this setup is suitable for long term remote operation with little maintenance. The precision achieved for all species is within or close to the project requirements. The comparison between the in-situ and flask sample results, used to verify the accuracy of the in-situ measurements, showed no significant difference for CO₂, O-2/N-2, CH₄ and N₂O, and a very small difference for SF₆. The same comparison however revealed a statistically significant difference for CO, of about 6.5 ppb, for which the cause could not be fully explained.