English Abstract Sediments in the harbours of Rotterdam contain
relatively large amounts of naturally occurring radionuclides resulting from
emissions of the ore-processing industries (Be88, Be92). Using harbour
sludge as a landfill for polders has locally caused the Ra-226 contents of
the soil to be a factor of 4 higher than the expected Ra-226 background. In
polders where Ra-226 was measured, the Ra-226 surplus was found to be
proportional to the cadmium contents (MO92). Data on cadmium contents are
available for many polders and therefore, cadmium may be useful as a tracer
for enhanced levels of Ra-226. Enhanced levels of Ra-226 may cause higher
radon concentrations in dwellings that are built on these soils. Therefore,
an extensive research programme is started to study the relation between the
Ra-226 contents of the soil and radon concentrations in dwellings. The
Laboratory of Radiation Research of RIVM has proposed to set up a
sub-programme, focusing on the sites where harbouw sludges have been dumped,
with the following goals: 1) to investigate if there are dwellings with
enhanced radon concentrations as a result of a Ra-226 surplus and 2) to
investigate if the relation between the Ra-226-surplus and the cadmium
contents found is generally valid and useful. In this report we describe
how this sub-programme may be set up and give specific advice on the answers
to various choices. We propose a.o. to use soil samples from 30 polders to
investigate the relation between the Ra-226 surplus and the cadmium contents
and to study in eight polders the possible consequences of enhanced Ra-226
levels for the radon concentrations in dwellings. Because the radon
measurements take one year (four measurements averaged over three months) we
propose that simple diagnostic measurements are made simultaneously with the
radon measurements. These additional measurements include measurements of
the groundwater table and of the effective ventilation pattern in the
dwelling.
