Monitoring Atmospheric Constituents

CO, CH4, and non-methane hydrocarbons (NMHCs) are important precursors of photo-oxidants. Therefore, these species have been measured at a number of TOR stations in western Europe. An interlaboratory comparison of the analytical methods employed by the various participating laboratories (PLs) and subsequent data harmonisation were performed to ensure data compatibility within TOR. The relative deviations of the PLs from the CO reference values by the Fraunhofer Institute for Atmospheric Environmental Research (IFU), acting as the central laboratory, covered the range from —2.21 to +2.38 percent, while the relative deviations of the PLs from the respective CH4 reference values were found to range from +0.66 to +2.31 percent. For most of the nineteen species considered in the intercomparison of atmospheric C2—C7 NMHC measurements, the relative deviations of IFU and the various PLs from the respective reference values U* for each round were found to typically fall into the range of -35 to +35 percent.