Detailed gas exchange measurements from two circular and one linear wind/wave tunnels are presented. Heat, He, CH4, CO2, Kr, and Xe have been used as tracers. The experiments show the central importance of waves for the water-side transfer process. With the onset of waves the Schmidt number dependence of the transfer velocity k changes from k o• Sc-2/3 to k o• Sc-•/2 indicating a change in the boundary conditions at the surface. Moreover, energy put into the wave field by wind is transferred to near-surface turbulence enhancing gas transfer. The data show that the mean square slope of the waves is the best parameter to characterize the free wavy surface with respect to water-side transfer processes. 1. , • !• 0.010 ! ß ß ! ß ß o o ! ß , ß ß 10 o 10 • 10 z ?requemcy [Hz] across the free aqueous viscous boundary layer, Tellus, in press, 1985b. J•ihne, B, G. Heinz, and W. Dietrich, Measurements of the diffusion coefficients of sparingly soluble gases in water with a modified Barrer method, submitted to J. Geophlts. Res., 1986. Kanwisher, J., On the exchange of gases between the atmosphere and the sea, Deep Sea Res., I0, 195-207, 1963. Kitaigorodskii, S. A., On the theory of the equilibrium range in the spectrum of wind-generated gravity waves, J. Phys. Oceanogr.., 15, 816-827, 1983. Kitaigorodskii, S. A., On the fluid dynamical theory of turbulent gas transfer across an air-sea interface in the presence of breaking wind-waves, J. Phys. Oceanogr., I4, 960-972, 1984. Kondo, J., Parameterization of turbulent transport in the top meter of the ocean, J. Phys. Oceanogr., 6, 712-720, 1976. Lange, P. A., B. J•hne, J. Tschiersch, and J. Ilmberger, Comparison between an amplitude-measuring wire and a slope-measuring laser water wave gauge, Rev. Sci. Instrurn., 53, 651-655, 1982. Ledwell, J. R., Gas ezchange across the air-water interface, Ph.D. thesis, Harvard Univ., Cambridge, Mass., 1982. Ledwell, J. R., The variation of the gas transfer coefficient with molecular diffusity, in Gas 2•nsfer at Water Surfaces, edited by W. Brutsaert and G. H. Jirka, pp. 293-302, D. Reidel, Hingham, Mass., 1984. Liss, P.S., Processes of gas exchange across an air-water interface, Gas exchange dependency on diffusion coefficient: Direct 222Rn and SH• comparisons in a small lake, J. Geophlis. Res., 87, 546-556, 1982. Weit•er, F., Verdunstungsmessungen in einem ringf6rmigen Wind-Wasser-Kanal mir Hilfe yon Psychrometern und einem WLD-System, Staatsexamensarbeit, Inst. filr Umweltphys., Univ. Heidelberg, 1980. Witting, J., Effects of plane progressive irrotational waves on thermal boundary layers, J. l•uid Mech., 50, 321-334, 1971. Wu, J., Wind-induced drift currents, J. l•uid Mech., 68, 49-70, 1975.

A long-term mountain station series of tropospheric 14C data for the period 1959 to 1984 is presented. This series is considered representative of the higher altitude14C level over central Europe. Even tree-ring 14C levels from a rural ground level site in southern Germany are consistently lower (by Δ14Cdepression = −15‰ if compared with the mountain station summer average in atmospheric CO2). The rural tree-ring series is considered to represent the additional continental Suess effect at ground level without local contamination. This Suess effect decreases gradually with the distance from the ground (ie, source) level. We therefore estimate the additional continental Suess effect in the vegetation period to be Δ14Cdepression = −5‰ for the mountain station and −20‰) for a rural ground level site, respectively. Based on this assumption, yearly mean tropospheric 14C levels corrected for fossil fuel contamination and representative of the Northern Hemisphere are provided for use in global carbon cycle models.

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CFCs are useful tracers for age dating young water. Two critical assumptions are typically invoked: (1) the initial concentration needs to be known, and (2) the tracer must be stable. A series of 8000 CFC air data from four sites on the west European continent (from high‐alpine clean air down to urban sites) show site‐specific CFC excesses relative to the global background ranging from 125% at an urban site (Heidelberg) to only 30% at a rural site (Wachenheim). In both cases we find regular diurnal, weekly, and annual variations but also episodic variations due to changing air mass and sporadic local emission as well as a decrease of the CFC excess due to decreasing emissions in Europe. However, in soil air above the groundwater table the CFC excess variation is low‐pass filtered, allowing reconstruction of the site‐specific CFC input anomaly in relation to the global background. Thus local CFC soil air measurements can provide a valuable local correction factor for CFC dating and extend the applicability of CFC studies in specific environments. To investigate the chemical stability assumption, five field sites and two laboratory experiments show CFC 11 and CFC 12 degradation under anoxic conditions with degradation rates ranging from 0.05 up to 3×105 pmol L−1 yr−1. However, the CFC 12/CFC 11 degradation ratio is found to be constant over six orders of magnitude, with CFC 12 always being less reactive by a factor of about 10.