Radium in baggerspecie afkomstig uit het Rijnmondgebied

The radium concentration was measured in 25 samples of harbour sludge taken from the Rijnmond area (Rotterdam harbours and the Nieuwe Waterweg) in 2002. High radium levels were found near the former discharge points of the phosphate ore processing plants, confirming the results of previous campaigns. The results of these previous campaigns (1994-2001) were corrected for a calibration defect that had been indicated in an international comparison of measurements. The cause of this defect appeared to be radon leakage from the calibration samples, resulting in an overestimation of radium concentrations by 16%. However, this turned out to be of no consequence for the conclusions drawn in previous reports. For 2002, the highest radium concentration of about 209 Bq kg-1 was found in a sample from the Nieuwe Maas (NM-2). The average total amount of radium of industrial origin for 2000 to 2002 in the nine regularly probed sections showing the highest radium levels was found to be approximately half the average for the 1995-1997 period. This is probably the effect of the former industrial releases, which, although decreasing, has not disappeared completely