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Evaluation of the combined Helium/Radon in Soil Gas Mapping Methodology as an Indicator of Areas in which Elevated Indoor Radon Concentrations may be found

Objective


A survey area of some 25 square kilometers was chosen, centred on the town of Claremorris, Co. Mayo, western Ireland. This area was selected because it is underlain by well-bedded, crystalline, Lower Carboniferous limestone, and because no information existed on the domestic indoor radon concentrations. It therefore, provided an ideal testing ground in which to evaluate and assess the predictive capacity of the combined He/Rn in soil-gas mapping technique in identifying high radon potential areas. Preparatory work for the project was carried out by RPII in Spring 1993 through a publicity campaign involving local media and public meetings. A vacant house with elevated indoor radon levels was secured for the project team at Milltown, Co. Galway some 15 km SE of the Claremorris survey area. An integrated field campaign by the project team was undertaken in May 1993 and May 1994.

Indoor radon gas measurements were carried out by RPII and over 1200 radon dosemeters were issued to householders during the course of the project. Local detailed geophysical surveys were carried out by University College Galway (under subcontract to RPII) at the test house site in Milltown, and at Eskerlevalla (Area 1) and Mount St. Michael Primary School (Area 3) in support of the indoor radon and soil-gas radon surveys. A geochemical analysis of a suite of soil/rock samples taken from the survey areas was completed by RPII using high resolution gamma spectroscopy.

A reconnaissance or low-density sampling survey of soil-gas radon and helium concentrations was carried out by Enmotec together with detailed soil-gas surveys (high-density sampling) in three selected sub-areas, Eskerlevalla (Area 1), Lugatemple (Area 2) and Mount St. Michael Primary School (Area 3) in Claremorris, and at the test house site in Milltown, Co. Galway. A total of 526 soil-gas samples were analysed by Enmotec for Rn-222 with 179 samples analysed for helium by the US Geological Survey.

Reconnaissance mapping of the bedrock geology and glacial geology was completed by GSI for both the Claremorris and Milltown survey areas. All extant geological data in GSI files was compiled and provided to the project team together with topographic base maps for the survey areas.

At the test house in Milltown, Co. Galway a detailed programme of continuous monitoring of soil-gas radon concentration at 1 m depth; radon concentration at 50 cm depth beneath the floor slab; indoor radon concentration at several locations within the house; pressure differences between indoor air, subslab air and outdoor air, and temperature differences between indoor and outdoor air was carried out by Gottingen during the two week field campaign in May 1993. Gottingen also constructed, calibrated and field tested a special soil probe for continuous measurement of the vertical radon gas profile in soil down to a depth of 3.5 m. The field testing of the probe took place in Germany during 1995.
IT IS IMPORTANT THAT EFFECTIVE RADON MAPPING METHODOLOGIES BE DEVELOPED WHICH WOULD COMPLEMENT AND ASSIST THE CURRENT INDOOR RADON MONITORING STRATEGIES OF EC RADIOLOGICAL PROTECTION INSTITUTES.
THE PROJECT AIMS
(A) TO ASSESS THE EFFECTIVENESS OF THE HELIUM/RADON IN SOIL GAS MAPPING METHODOLOGY AS AN INDICATOR OF AREAS IN WHICH ELEVATED INDOOR RADON CONCENTRATIONS MAY BE FOUND.
(B) TO INVESTIGATE THE TEMPORAL AND SPATIAL PATTERNS OF INDOOR RADON CONCENTRATIONS IN HOUSES.
(C) TO INVESTIGATE THE VARIATIONS INRADON EXHALATION FROM THE GROUND DUE TO METEOROLOGICAL CONDITIONS, AND
(D) TO IMPROVE OUR UNDERSTANDING OF THE GEOLOGICAL FACTORS WHICH CONTROL THE GENERATION, MIGRATION AND INGRESS OF RADON INTO HOUSES.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

RADIOLOGICAL PROTECTION INSTITUTE OF IRELAND
Address
Clonskeagh Square 3
14 Dublin
Ireland

Participants (3)

Enmotec Ltd
Germany
Address
Bismarckstraße 80
72072 Tübingen
Geological Survey of Ireland
Ireland
Address
Beggars Bush - Haddington Road
4 Dublin
Georg-August-Universität Göttingen
Germany
Address
Burckhardtweg 2
37077 Göttingen