Natural radon and phosphorus as limnologic tracers: Horizontal and vertical eddy diffusion in Greifensee

Abstract

Two‐dimensional interpretation of monthly measurements of natural radon‐222 at different stations in Greifensee, Switzerland, results in hypolimnetic vertical and horizontal eddy diffusion coefficients (Kz and Kx) of 0.2–0.05 and 1,000–100 cm2 s−1 during the stagnation period in 1975. Application of the one‐dimensional and three‐dimensional horizontally well mixed models to the data from the midlake station produces errors of about a factor of two in the vertical eddy diffusion coefficient. With the hypolimnion mixing information, Kz in the thermocline is estimated to be 0.025 ± 0.015 cm2 s−1 by using dissolved phosphorus as a quasi‐conservative tracer.The eddy diffusion coefficients calculated are in good agreement with those which would be predicted by empirical methods. The results when applied to phosphorus cycling indicate that P reflux from the hypolimnion and thermocline in eutrophic Greifensee is of the same magnitude as external inputs during the months of maximum photosynthesis.