Measurements of concentration, 13 C/ 12 C and 18 O/ 16 O ratios of tropospheric carbon dioxide over Switzerland

In 1982, we collected air sample profiles approximately monthly from aircraft at altitudes up to about 7 km and analyzed them for CO 2 concentration and stable isotope composition. The following seasonally detrended mean values were obtained per 1 January, 1982: 338 ppm, δ 13 C=-7.72‰, δ 18 O = -0.6‰ (versus PDB); isotopic results are corrected for N 2 0 contribution. CO 2 results are discussed in terms of vertical eddy diffusion and of a mean annual vertical flux. Assuming a two-component mixture between background air and biospheric CO 2 , δ 13 C of the biospheric component is -26.2‰, in good agreement with other northern hemisphere results. δ 18 O varies seasonally, but with relatively much scatter. The oxygen isotopic composition of CO 2 is determined by exchange with vegetation, soils and ocean; these processes are discussed in detail. DOI: 10.1111/j.1600-0889.1987.tb00272.x