Sediment cores from central Lake Constance were dated with Zl~ and [37Cs. A sedimentation rate of(0.11 :t:0.02) g-cm-2.y -I was determined with the 21~ method. 137Cs measurements revealed sedimentation rates of (0.11+0.01) g.cm--~.y -t and (0.08:1:0.01) g.cm-2-y -I, respectively for two different cores sampled at the same location. The lower Cs-dated value indicates incomplete core recovery and demonstrates the sensitivity of this simple dating method to small losses of material at the water/sediment interface. An unambiguous application of the 137Cs method is, therefore, only possible if complete core recovery is ensured. Sedimentation rates based on particulate matter, collected in sediment traps at various water depths, agree with the results of the radioisotope methods. Estimates of 30-125 days residence times for suspended particulate matter were calculated from 7Be meausurements.

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The concentrations of volatile elements in grain‐size separated agglutinate and mineral fractions of samples 76240 (permanently shadowed) and 76260 were compared in heating experiments. The surface concentrations of Hg were found to be considerably higher in the shadowed sample. For the rest of the investigated elements only small or insignificant differences in the concentrations were observed between the two samples which differ in the storage temperature during the last 104 y. The difference in the concentrations of Hg must be the result of the shadowing. Based on the present investigation and on our earlier heating experiments, it can be concluded that Hg and Cd are mobilized by solar heating of the uppermost lunar soil and are trapped in cold places on the moon. This low‐temperature volatilization leads to a redistribution of volatiles (e.g., Hg and Cd) on the lunar surface.

Heavy ion reactions /Actinide targets /Fast radiochemical separation /Ra to Am AbstractA procedure is presented for a relatively fast (20 to 30 min) separation of trace amounts of americium, plutonium, neptunium, uranium, protactinium, thorium, actinium and radium. Isotopes of these elements, produced in heavy ion reactions with actinide targets and collected by recoil in copper catcher foils, can be separated from each other and from contaminating activities. The element fractions were sufficiently clean for determinations by gamma-ray and/or alpha spectroscopy.

A heating technique is described which permits investigation of small samples (10-100 mg) of material originating from natural or technical processes. The distribution of trace elements throughout mineralogical samples was measured. It is demonstrated that mechanisms leading to surface coatings can be studied. This apparatus was developed for the investigation of small lunar samples.