VERTICAL-DISTRIBUTION AND TRANSPORT OF MOLYBDENUM IN A LAKE WITH A SEASONALLY ANOXIC HYPOLIMNION

Distribution and trends of Mo concentrations in the seasonally anoxic Lake Greifen were investigated over 15 months. Mo in water samples and settling particles was determined by catalytic adsorption polarograph y and inductively coupled plasma mass spectrometry. Mo concentrations in the epilimnion were usually homogeneous at approximately 0.48 mug l iter-1. A significant decrease with depth was found during the stratif ication period. The lowest Mo concentrations (0.31 mug liter-1) were f ound in the presence of H2S near the sediment. A vertical flux of part icle-bound Mo of 1. 1-4.6 mug m-2 d-1 was found. The Mo concentration- depth profiles result from a combination of different transport mechan isms that are compared by computer model calculations.