Radioactivity

An Investigation of Uranium Series Radionuclides in Water Supplies, Wastewaters and Sludges in Ireland.

Summary

A multidisciplinary (chemical, analytical, radiological and health physics) research study is underway, to investigate radionuclide speciation and behaviour in water supplies, wastewaters and sludges in Ireland.

In addition to sludges, water supplies from associated regions will be tested. In particular, water supplies from an area of elevated natural radioactivity (Donegal) will be examined, as a follow on from a previous study.

The project will investigate screening and analytical methods for a range of uranium series nuclides and assess likely impacts to target populations utilising such water supplies, or receiving the products of wastewater treatment (discharges or sludges). Novel techniques involved include gamma and alpha spectrometry, ICPMS and scintillation counting with a concomitant assessment of their efficiency and effectiveness. The project will provide a framework for the prediction of radionuclide contamination in drinking water, wastewater and sludges nationally.

The project involves direct collaboration with Prof. Peter Mitchell of University College Dublin.

The Research Team

Mr. John O’Dea Principal researcher Department of Environmental Science, IT, Sligo .

Prof. Peter Mitchell Associate researcher University College Dublin

Dr. Ted McGowan Associate researcher

(ICPMS) Department of Environmental Science, IT, Sligo .

Ms. Carmel Moran Post-Graduate Student Department of Environmental Science, IT, Sligo .

Background

The proposed project will involve the characterisation and speciation of uranium series radionuclides in a number of water supplies, wastewaters and sludges in Ireland . This will involve the use and comparison of a number of analytical methods, some of which have not been used in Ireland in this subject area.

Donegal is chosen as a special area of interest because it is recognised as an area of elevated natural radioactivity (O’Connor et al, 1986), and also because it involves a follow on from a previous study.

Otton et al (1988) describe the occurrence of anomalous U levels in waters draining from a mountain range in Nevada , the rocks of which contain on average 7.2 ppm of U and identify such waters as posing a threat to target populations. O’ Dea and Dowdall (1999) found similar values in the Barnsmore region of County Donegal . The Radiological Protection Institute of Ireland carries out a limited radionuclide, grab sample, analysis of water supplies. A number have been found to exceed WHO and EPA (US) guidelines for gross alpha and Ra activity (RPII, 1997).

Interest and concern in the levels of Ra-226 in drinking water have increased since the setting of the above guidelines. The EPA (US) is revising its radionuclide regulations for drinking water which include U (10 pCi/l), Ra (5 pCi/l) and Rn (10,000 pCi/l) (NRC, 1999). These values are frequently exceeded in data found in the literature (Szabo and Zapecza, 1987).

A comparison of RPII values for total gross alpha with those of the Scottish EPA (SEPA, 1998) reveal higher values in Ireland, a situation that is either indicative of high levels of radionuclides in Irish waters or disparity in the results based on analytical methods used, both topics being addressed in the proposed study and highlight the value of such work. In this study, concern about drinking waters extends to other elements of the life-cycle of water, namely wastewater and the products of wastewater treatment (sludges).

The project will involve detailed sampling of a number of water, wastewater and sludge sources, with subsequent chemical and radio-analytical analyses. The analytical techniques will include standard chemical analysis (pH, Eh, metal content, organic carbon, anion content etc.) and more advanced isotopic analytical procedures utilising the Inductively Coupled Plasma Mass Spectroscopy and gamma and alpha spectroscopy. Ultra-filtration and hydro-geochemical modelling will be employed to chemically characterise the mode of occurrence of radiological contaminants within the water supplies.

Accepted monitoring methods in the US have been shown to have unacceptable weaknesses (Holbert et al, 1995) related to site specificity and such techniques require testing under local conditions prior to implementation on a national scale. Radioanalytical procedures will thus be centred on the identification and validation of a radioanalytical method suitable for the rapid assessment of radionuclide levels in surface waters. Techniques investigated will include alpha spectrometry, high resolution gamma spectrometry, scintillation techniques ( Lucas cells) and accepted US-EPA methods.

Project Details

Analytical techniques will be developed and validated. This involves the investigation of the applicability and practicability of a range of accepted methods and adaptation of these to suit the parameters being investigated. Selected methods will be validated with respect to chosen analytes using international traceable reference standards and accepted statistical procedures.

Study sites and target populations will be identified via use of maps and census information along with contact with and advice from appropriate local authorities and with reference to the Regional Sludge Treatment Centres.

Specialist training in an alpha spectroscopy laboratory will be required. Sample preparation is crucial to the success of an alpha analysis making this training period essential to the success of the project. The student researcher will spend two months in the Radiation Physics and Radioecology Research Laboratory in the Physics Department in University College Dublin. This is run under the supervision of Dr. Peter Mitchell who is Ireland ‘s foremost radioecologist and has an international reputation in this area.

Initial/pilot sampling of sites will be carried out. Preliminary samples will be analysed by chosen methods including ICPMS, gamma and alpha spectroscopy, ion chromatography and radon bubbling.

A full sampling regime will be carried out in accordance with the results of the pilot study. Samples will be prepared and analysed (separation, extraction and interference correction), subject to the results of method development and validation.

Results will be interpreted in conjunction with data from other projects in the programme (i.e. Biosolids 1[Characterisation of the physical/chemical and biological profile of a range of municipal and industrial sludges], and Biosolids 6 [An investigation of soil quality parameters relating to agricultural reuse and land disposal options for the management of sludges].

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