Experience with a continuously operating water sampling system

Grab sampling, as used usually for taking water samples, has clear practical advantages, but is not sufficient from the conceptual point of view when changes in the activity concentration have to be expected in the sampling interval. The paper is concerned with experience gathered with some continuous water sampling systems which are operated for some time in the Danube river. Both practical and conceptual aspects of the continuous technique are discussed. The discussion includes problems of setting in operation of the equipments as well as operational difficulties. Eventually, the results obtained with the continuous sampling system are compared with those from grab sampling. 1 ref., 1 fig. (Author)