Carbon dioxide and methane in continental Europe: a climatology, and ²²²Radon-based emission estimates

Abstract

4-year records of gas chromatographic carbon dioxide and methane observations from the continental mountain station Schauinsland in the Black Forest (Germany) are presented. These data are supplemented by continuous atmospheric 222 Radon observations. The raw data of C02 concentration show a large seasonal cycle of about 16 ppm with monthly mean wintertime enhancements up to 10 ppm higher and summer minima up to 5 ppm lower than the maritime background level in this latitude. These offsets are caused by regional and continental scale CO2 sources and sinks. The mean CH4 concentration at Schauinsland is 31 ppb higher than over the Atlantic ocean, due to the European continent acting as a net source of atmospheric CH4 throughout the year. No significant seasonal cycle of methane has been observed. The long term C02 and CH4 increase rates at Schauinsland are found to be similar to background stations in the northern hemisphere, namely 1.5 ppm C02 yr" 1 and 8 ppb CH4 yr-1. On the time scale of hours and days, the wintertime concentrations of all three trace gases are highly correlated, the mean ratio of CH4/C02 is 7.8 +1.0 ppb/ppm. The wintertime monthly mean concentration offsets relative to the maritime background level show a CH4/C02 ratio of 6.5 + 1.1 ppb/ppm, thus, not significantly different from the short term ratio. Using the win tertime regressions of C02 and 222 Radon respectively CH4 and 222 Radon we estimate winter time C02 flux densities of 10.4 + 4.3 mmol C02 m-2 h-1 (from monthly mean offsets) and 6.4 + 2.5 mmol C02 m~2 h" 1 (from short term fluctuations) and winter time methane flux densities of 0.066 + 0.034mmol CH4 m~2 h" 1 (from monthly mean offsets) and 0.057 + 0.022 mmole CH4 m~2 h" 1 (from short term fluctuations). These flux estimates are in close agreement to C02 respectively CH4 emission inventories reported for Germany from statistical data.

Ground based radon-222 observations and their application to atmospheric studies

“…There is an alternative approach for the estimation of surface-atmosphere exchange of climatically active gases that has been successfully employed by a number of researchers (Gaudry et al, 1990;Schmidt et al, 1996;Wilson et al, 1997;Biraud et al, 2000). The technique involves the comparison of concentration measurements of a reference and companion trace gas.…”

“…Taking the ratio of Eq. (6), formulated for radon, r, and a companion gas, c, yields an expression for the radon-calibrated surface flux of the companion gas (Schmidt et al, 1996;Wilson et al, 1997) …”

“…The annual cycle of methane is typically less pronounced than that of CO 2 (Biraud et al, 2000), and its predominant sink mechanism (OH oxidation), can be neglected on short time scales (Schmidt et al, 1996). Estimates of CH 4 emission from western Europe by Biraud et al (2000) ranged from 3.5 to 4:8 Â 10 3 kgCH 4 km À2 year À1 , a close match to independent estimates of CH 4 emission for the region by Derwent et al (1998) and Ryall et al (1998) that ranged from 3.9 to 7:3 Â 10 3 kgCH 4 km À2 year À1 .…”

“…The authors argued that although total errors may be larger, they are random and partially compensated for by averaging. Schmidt et al (1996) estimated CO 2 fluxes using the radon-calibrated flux technique at the catchment scale from an elevated site in Germany. Upslope and drainage winds associated with the local topography added further complexity to the selection criteria in this study.…”

Source characteristics of O3 and CO2 at Mt. Waliguan Observatory, Tibetan Plateau implied by using 7Be and 210Pb

“…7 Be does not imply that air mass from downward transport dissipate the surface high CO 2 concentration in winter. The summer negative correlation coefficient of 210 Pb and CO 2 even suggests that CBL emission is a net sink for CO 2 , which obviously conflicts with the realities because the mother of 210 Pb is 222 Rn, the first hand tracer of soil emission, positively correlates with the surface CO 2 [25].…”