Skip this Video
Download Presentation
Radon in groundwater Analysis of causes and development of a prediction methodology

Loading in 2 Seconds...

play fullscreen
1 / 51

Radon in groundwater Analysis of causes and development of a prediction methodology - PowerPoint PPT Presentation

  • Uploaded on

Radon in groundwater Analysis of causes and development of a prediction methodology. Skeppström K. PhD. Student Dept. of Land and Water Resources Engineering, KTH. Layout of presentation. Radon (focus of Rn in groundwater) Objective of project / Phases involved Methodology

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about ' Radon in groundwater Analysis of causes and development of a prediction methodology' - cedric-grimes

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Radon in groundwater

Analysis of causes and development of a prediction methodology

Skeppström K.

PhD. Student

Dept. of Land and Water Resources Engineering, KTH


Layout of presentation

Radon (focus of Rn in groundwater)

Objective of project / Phases involved


Results & Discussions

  • Radioactive
  • Colourless, odourless, noble gas
  • Exists as 3 main isotopes:
  • 222Rn (uranium decay series, 238U),Half-life ( T1/2) = 3.8 days
  • 220Rn (Thorium decay series, 232Th), T1/2 = 56 seconds
  • 219Rn (Actinium decay series, 235U), T1/2 = 4 seconds
  • Cancer risk
    • 500 cases of lung cancer/year in Sweden; smokers have a higher risk.
    • Risk of developing of other cancers ?






Uranium decay series

238U (parent)








 + 

206Pb (stable)


 + 

genomsnittlig rlig str ldos i sverige
Genomsnittlig årlig stråldos i Sverige

Source: Statens Strålskyddsinstitut

exposure routes


Construction material

Soil gas / bedrock (Granite)

Exposure routes
radon problems in water
Radon problems in water

Surface water


Dug wells

(soil/sand aquifer)

Drilled wells

(Hard rocks)

how radon in water is a problem
How radon in water is a problem?

1000 Bq/l

in water

100 Bq/m3 in air

Dish washing 95 %

Shower 60 – 70 %

Bath 30 – 50 %

Washing machine 90 – 95 %

Tap water 10 – 45 %

WC 30 %


Radon in water

Radon emanated in mineral grain escape in the pore space




Presence of parent elements, 238U or 226Ra

  • Transport mechanisms
  • Diffusion
  • Convection

Pore space filled with water- Radon dissolves in the water

  • Dosimetry
  • 1000 Bq/l is dangerous

Water extracted from drilled wells (fracture water)

How is it

a problem ?


Precipitation of 238U 234U, 230Th, 226Ra from water to surface of fracture

Leaching of 238U and 234U

Emanation of 222Rn

Content of 238U in the rock: 10ppm

222 Rn

Concentration of 222Rn in Bedrock: 0.33Bq/m3 rocks

Concentration of 222Rn in groundwater: 5 milj Bq/m3


Radon Emanation

Radium atom

Radon atom

Mineral grain



Radon risk in Sweden

Groundwater radon risk map of Sweden

(after Åkerblom & Lindgren, 1997)

any deduction
Any deduction?

Granite types of rocks with high uranium concentration

High radon concentration in water

 not always the case


Hypothesis of project

  • The hypothesis stipulates that the occurrence of radon from groundwater is governed by a number of well-defined factors ranging from:
  • Geological (bedrock, soil, tectonic structures, flow pattern and surrounding environment)
  • Chemical (oxidation reaction, other processes in water)
  • Topographical (difference in elevation and slope that determine flow pattern and renewal tendency and frequency)
  • Technical(withdrawal system & frequency which determine circulation as well as ventilation possibilities.

Purpose of research

  • Map processes and factors influencing radon content in groundwater
  • Develop a prediction model, based on statistics, that can be used to determine areas at risk.

Phases of the project

Using GIS and multivariate analysis of

data to assess factors affecting radon

concentration – REGIONAL LEVEL

Phase 1

Detailed study at Ljusterö to determine

spatial & temporal variation of radon

concentrations due to a range of factors.


Phase 2

Development of risk prediction model

Phase 3


Phase 1

  • Data collection from:
    • Swedish National Land Survey (elevation and landuse data)
    • Swedish Geological Survey, SGU (soil & bedrock geology, fractures, radiometric)
    • Municipalities (data about wells and radon content)
  • Data transformation and extraction using ArcGIS and its spatial analyst function
  • Statistical analyses including multivariate

analysis of data.


Factors considered

  • Elevation
  • Soil geology
  • Bedrock
  • Fracture zone
  • Landuse
  • Uranium content


  • Derived factors
  • Altitude difference
  • Predominant soil, bedrock, landuse within a certain vicinity e.g. 200 m
  • Slope of the terrain
geographical information system gis
Geographical Information System (GIS)
  • GIS is a computer system for managing spatial data.
  • Purpose of GIS
      • Organisation
      • Visualisation
      • Spatial Query
      • Combination
      • Analysis
      • Prediction
what is my objective
What is my objective?

For each well, relevant spatial patterns need to be extracted from the factor maps

To generate continuous surfaces with a spatial resolution of 50 m


Derive factors

Data obtained in different formats, e.g ASCII, point vector


Software: ArcMap

Spatial analyst function

Geostatistical software

Ultra edit


statistical methods
Statistical methods
  • Which method?
  • Relate radon concentration with a large number of variables
  • Variables are both qualitative and quantitative in nature
  • Non-normal distribution of many variables
  • Use of covariance and correlations ? Careful with the interpretations
      • Not much information about association between variables
      • Non-linear associations can exist
      • Very sensitive to ‘wild observations- outliers ’

Statistical Analyses

  • Use of multivariate analysis of data
    • Each observational unit is characterised by several variables.
    • It enables us to consider changes in several properties simultaneously
    • Non normality of data (non parametrical tests)
  • Statistical Methods
    • Analysis of variance
    • Principal Component Analysis (PCA)
pca method
PCA method
  • Eigenvectors of a variance-covariance matrix
  • Linear combinations of these variables
  • Its general objectives:
      • Data reduction (A small amount of k components account for much of the variability of the data)
      • Interpretation (may reveals relationships that were not previously suspected)



Non-outlier range


Summary of results

  • High radon concentration in drilled wells is related to:
    • Low altitude
    • Granite rocks
    • Close distance to fracture
    • When overlying geology is lera/silt
    • Infrequent use of wells (summer houses)
    • An overview of the terrain in the surrounding of the wells (flat or hilly) is also of interest in connection to groundwater flow tendencies and speed of flow.
risk variable method

Data collection

Preparation Phase

(Expert system)

Statistical analyses

Expert assessment

Selection of significant variables

Operational phase

(User Interface)

Define study area

Determination of risk values

Determination of uncertainty values

Suming up risk and uncertainty values

Final Risk Evaluation

Risk Variable Method
risk variable modelling rvm
Risk Variable Modelling (RVM)

V1 x R1 + V2 x R2 + V3 x R3 + ……….+ Vn x Rn = FRV

FRV = Final risk value

  • Where Vi= a risk value for a specific variable (-2 to +2)

Ri = the rating of the variable (1 to 3)


Field studies at Ljusterö

  • Why Ljusterö?
  • Number of wells = 198
      • 141 wells exceeding 500 Bq/l (71%)
      • 96 wells exceeding 1000 Bq/l (48%)
  • Radon concentration
      • Mean = 1942 Bq/l
      • Minimum = 50 Bq/l
      • Maximum = 63560 Bq/l

What was done?

To choose 3-4 study areas on Ljusterö, exhibiting drastic fluctuations in the radon concentration and to perfom detailed study at these locations


Detailed study

  • Analysis of geology (bedrock type, fracture zones, tectonic zones and fracture filling minerals, soil type and soil depth)
  • Altitude and other terrain considerations
  • Analysis of technical factors (wells technical design, hauling system, spatial temporal extraction patterns of wells)
  • Radiometric measurements of radiation (from soil around wells as well as measurements of radiation in wells and in tap water)
  • Chemical analyses in water samples (U, Ra, Rn, fluoride and other water components)