Phosphogypsum discharges by phosphate-ore processing industries pollute sediments of the Rotterdam harbour area with226Ra. Direct measurement of this radionuclide in sediments does not provide a reliable indication of the elevation of the levels,
since226Ra levels in sediments depend on the particle size. To eliminate the size effect, the226Ra/Ba ratio in sediments was tested as a possible indicator for the226Ra in the discharges. The results indicate almost a doubling of the226Ra levels in sediment samples due to phosphogypsum discharges. The contribution of phosphogypsum to the sediment mass was
calculated in the order of a few percent equivalent.