KTH
Mark- och Vattenteknik
KTH / Institutionen för Mark- och Vattenteknik / Forskningsprojekt
Radon in groundwater. Analysis of causes and development of a
prediction methodology
Project leader: Bo Olofsson
Participants: Kirlna Skeppström
Key words: Radon, groundwater, prediction methodology, , vulnerability, Risk Variable Method
Project period: 2003-01-01 - 2005-12-31
Funding: SGU
Background
Radon is, next to smoking, the biggest single risk factor for lung cancer and high contents of radon
in air are assumed as a serious threat to health. Radon is added to a building from the construction
material, from the ground or through the tap water. The knowledge of the radon problem in
groundwater in Sweden has grown during 1990:s due to an increased number of deeply drilled
wells in hard rock. A summarising of data from the counties of Sweden (SOU, 2001), shows that
more than 50% of the drilled wells have a radon content higher than 100 Bq/L and more than 10%
of the wells a content higher than 1000 Bq/L. The causes to the high radon content in drilled wells
are not fully explained. Statistically, there is a connection to some rock types such as young
granites and pegmatites with uranium and thorium fracture minerals. However, the pattern is not
clear and some investigations also show that the well construction and the discharge pattern affects
the content of radon. There are also significant differences in the radon content between various
areas with different topography and different soils. If the causes to high radon content in drilled
wells would be known, it would be possible to predict high radon content in groundwater, which
in turn is important within the municipal planning.
N
N
Wells with radon
analysis in the county
of Stockholm
0km
20km
40km
Radon risk areas
calculated using
kriging.
(White areas have
too few wells)
0km
20km
40km
Rn (Bq/L)
1000
500
100
0
Fig.1.
Radon measurements in drinking water from private drilled wells in the county of
Stockholm and a preliminary risk map calculated from existing wells. (Based on data from
Stockholm County Board 2000). (Knutsson & Olofsson, 2002).
Aim
The aim of the project is to clarify the natural and technical factors and processes affecting the
radon content in drilled wells and, based on that, develop a prediction methodology for radon in
drilled wells.
Method
The project comprises analyses of radon wells in three scales, a regional overview, a local
municipal and a detailed time dependant. The regional study is carried out using general digital
information in the county of Stockholm. A database is built up in a GIS (Geographical Information
System). Statistical multivariate analyses are carried out. The regional study is made within a part
of a municipality using digital information (GIS), maps and field visits. The detailed studies are
carried out in a small area (a small part of a municipality) in connection with extensive field
studies of geology, tectonics, fracture minerals and water chemical sampling. The sampling is
repeated in order to identify seasonally variations. Based on statistically documented correlations
between radon content and various natural and technical factors, a vulnerability prediction method
is developed, using RVM (Risk Variable Modelling).
Material/Database
A database consisting of about 6000 wells with radon analysis from the county of Stockholm is
used in the regional studies. In addition, the municipalities of Norrtälje and Österåker have
collected radon analyses from about 2000 drilled wells. The detailed studies are made on the
island of Ljusterö, where some building areas show very high radon values.
Cooperation
The project is conducted in cooperation with SGU and some municipalities in. the county of
Stockholm.
Published papers
Knutsson, G., Olofsson, B., (2002): Radon concentrations in drilled wells in the Stockholm region of
Sweden. Norges geologiske undersökelse (NGU) Bulletin 439, pp 79-85.
Skeppström, K., Olofsson, B., (2005): Radon in groundwater. Analysis of causes using GIS and
multivariate statistics. A case study in the Stockholm County. In Sugahara, T., et al (eds): Proc. 6th.
Int. Conf. On High Levels of Natural Radiation and Radon Areas, Osaka, Japan, 6-10 Sept. 2004. Int.
Congress Series, 1276, Elsevier.
Upp