-96/1
«)>««, 5. Lyons, , McGarry r r v O1 //I'/I.I1./, /)/f/\'/'l /•/ ~c'Y- - r -'i; •"•« j'i>
/^/. A/ifi/:L//£«:(//. /Li
l'iu\t'i\n\ Cvl!i'«t\ 1) il>!n: 4
1 : l "'•'•'; v-Jc; .'•-... •.-.•»••.,•'-v .'-' ."•'.•••?'• ..I'-.i.-- -!.-. -_ ;.'-:•.••.;*.:.•::,, •,-." "u .*•»,• .•"•' :- - Artificial Radioactivity in Lough Foyle
J.D.Cunningham, T.P. Ryan, S. Lyons, V. Smith and A. McGarry Radiological Protection Institute of Ireland Dublin 14
P.I. Mitchell andh. Leon Vintro Department of Experimental Physics University College, Dublin 4
R.A. Larmour and F.K. Ledgerwood Environment Service, Department of the Environment (N.I.) Belfast BT1 IFY
April 1996
NEXTPAGE(S) Uft BLANK CONTENTS
1 Introduction 2 Description of Lough Foyle 3 Methodology 4 Results and discussion 5 Radiological assessment 6 Conclusions 7 Acknowledgements
LIST OF FIGURES
Figure 1 Location of Lough Foyle on the Irish coastline Figure 2 Location of sampling sites in Lough Foyle
LIST OF TABLES
Table 1 Location of sampling sites in Lough Foyle Table 2 Radiocaesium in filtered sea water at shoreline stations in Lough Foyle Table 3 Plutonium and americium in sea water in Lough Foyle and Carlingford Lough Table 4 Physico-chemical speciation of plutonium and americium in sea water in Lough Foyle, Carlingford Lough and the Western Irish Sea
Table 5 Sediment-water distribution coefficients (Kds) for plutonium and americium in Lough Foyle, Carlingford Lough and the Western Irish Sea Table 6 Radiocaesium in sediment in Lough Foyle Table 7 Plutonium and americium in sediment in Lough Foyle Table 8 Particle-size distribution of sediments in Lough Foyle Table 9 Radiocaesium in Fucits vesiculosus in Lough Foyle Table 10 Radiocaesium in mussels and winkles in Lough Foyle Table 11 Plutonium and americium in mussels and winkles in Lough Foyle Table 12 Gamma dose-rate measurements at inter-tidal sites around Lough Foyle Table 13 Maximum levels of radionuclides in Lough Foyle in comparison with generalised derived limits
NEXTPAQE(S) toft BtANK 1 INTRODUCTION
The purpose of this study was to assess the extent to which the marine environment of Lough Foyle, situated on the north coast of Ireland (Figure 1), lias been affected by artificial radioactivity released from Sellafield. To this end, the concentrations of radiocaesium, plutonium and americium were examined in seawater, sediment and biota in the Lough and compared with concentrations in similar samples from the north-western Irish Sea and in maritime zones affected solely by global fallout. The physico-chemical speciation of plutonium and americium in lough waters was also examined. Ambient gamma dose-rates in air above the inter-tidal sediments were compared with gamma dose- rates elsewhere throughout Ireland. Finally, some comparisons have been drawn between the results from this study and those from a similar study carried out in Carlingford Lough in 1990.
Both the Radiological Protection Institute of Ireland and the Environment Service of the Department of the Environment for Northern Ireland have been monitoring the impact of the Sellafield discharges on the Irish environment for many years [1, 2, 3, 4, 5]. In 1992 both organisations collaborated with the Radiation Physics Research Laboratory of the Department of Experimental Physics, University College, Dublin in a detailed study of the radioactivity levels in Carlingford Lough on the north eastern coast of Ireland [6], The last-named has extensively studied the behaviour and biological availability of transuranium and other long-lived radionuclides in the Irish Sea [7, 8, 9, 10, 11].
2 DESCRIPTION OF LOUGH FOYLE
Lough Foyle is part of the long valley of the River Foyle and runs roughly north and south between the peninsulas of Inishowen, Co Donegal and Magilligan, Co Londonderry. The entrance to the ocean, lying between the harder rocks of Inishowen and the basaltic cliffs at Magilligan, is narrow and almost converts Lough Foyle into an inland lake.
The metamorphic schists of Inishowen form the straight western shore, while the apex of the great sandy triangle of Magilligan on the east almost blocks the entrance to the lough, reaching across to within a mile of Greencastle on the opposite side. Further up, the eastern shore is recessed and the lough expands to its maximum width of about 13 kilometres. The lough is about 24 kilometres long and the City of Derry is situated about 6 kilometres up the River Foyle. A considerable volume of fresh water flows from the River Foyle which is tidal as far as the town of Strabane.
Lough Foyle is shallow and has banks and shoals of sand and mud on the eastern side, many of which are exposed at low tide. The entrance to the lough has a depth of 18 - 20 metres but otherwise the deepest part is a channel of 11-18 metres running close to the western shore. Elsewhere the depth ranges from 0.5 - 7.5 metres. The bottom of the lough is mainly sand and mud. The tidal range at Lough Foyle is low and consequently a wide expanse of shore is not exposed. Mud-flats, boulders 40 00 I I
ATLANTIC OCEAN
NORTHERN!"-? IRELAND (kSellafield
FIGURE I Location of Lough Foyle on the Irish coastline and outcrops of low-lying rock occur on the western side of the lough with some sandy shores. On the eastern side a certain amount of land reclamation has taken place and there is considerable industrial development along the coastline. Important fishing activities are centred at Moville and Greencastle in Donegal.
3 METHODOLOGY
Sampling
The sampling sites in Lough Foyle are shown in Figure 2 and the types of samples taken at the different sites are listed in Table 1. Samples of coastal sea water (50 - 100 litres), surface sediments (0-5 mm), seaweed (Fucus vesiculosus), mussels (Mytilus edulis) and winkles (Littorina littorea) were collected from the inter-tidal zone around the coastline. In the case of sediments, two samples were collected at points 50 metres apart at each location. Dose-rate measurements
Gamma dose-rate measurements were made one metre above the ground over inter-tidal sediments on both sides of the lough using energy compensated Geiger-Mueller detectors, suitable for environmental measurements of gamma radiation. Each instrument was calibrated using standard calibration sources and intercomparisons were made between instruments to ensure uniformity of response.
Sample analysis
Samples were taken to the laboratories of the Radiological Protection Institute of Ireland and University College Dublin after some preliminary treatment on-site. Seaweeds, sediments and the edible portions of shellfish were dried, ground to a powder capable of passing through a 0.22 mm mesh and packed into standard containers for gamma spectrometric analysis. For the analysis of radiocaesium in sea water, samples were acidified on collection and filtered through 0.45 micron (jam) Millipore filters on the day of collection. Radiocaesium was extracted from the filtered sea water onto an ion-exchange column of silica gel impregnated with ammonium molybdophosphate.
Gamma emitting radionuclides (e.g., caesium-137, caesium-134, etc.,) were analysed by high resolution gamma spectrometry. Efficiency calibration was carried out using a certified reference standard and quality control was maintained by participation in national and international intercomparison exercises.
Measurements of the particle-size distribution of the sediment samples were made. The samples were first freeze dried to ensure that the particles were segregated without mechanical attrition. Each sample was passed through a series of British Standard test sieves down to a size of 125 jum. The material passing 250 jum was further sized down to 2 pm using a Malvern 2600 Particle Sizer. Ultra- sonic treatment was used to disperse the solid throughout the water carrier. The particle-size distributions of the fractions passing 250 fan were measured in triplicate using a laser diffraction technique.
For the determination of plutonium and americium in samples of sea water, sediment and biota, standard radiochemical procedures were used to separate and purify plutonium and americium prior to measurement by high resolution alpha spectrometry.
The reduced and oxidised forms of plutonium in filtered sea water were separated by the neodymium fluoride coprecipitation method [12]. The fractions of the plutonium and americium which were colloidally bound in sea water were determined by passing the sample through a set of four aluminium oxide beds arranged in series after the method of Nevissi and Schell [13, 14]. In this technique the colloidal fraction is defined as that which can pass through a 0.45 jtm filter but is efficiently sorbed on the first aluminium oxide bed and may be quantified by the appreciably higher collection efficiency 10
kms \ Dunagree Point
COUNTY Greencastle DONEGAL Magilligan Point
Ballymacran
Donnybrewer Longfield
A Carrichu
Faughanvale COUNTY LONDONDERRY
CITY OF DERRY
FIGURE 2 Location of sampling sites in Lough Foyle on the first bed compared with the second, third and fourth beds [14J.
4 RESULTS AND DISCUSSION
Sea water
Concentrations of caesium-134 and caesium-137 in filtered sea water sampled at three coastline locations are given in Table 2. Caesium-137 concentrations, while readily detectable at Dunagree Point and Donnybrewer were, nevertheless, very low being in the order of about 10 Bq m"3. Both are at least a factor of five lower than the concentrations which prevailed in Carlingford Lough and throughout the western Irish Sea in 1992 [2, 6J. However, they are somewhat higher than the
8 caesium-137 'background' concentration in oceanic NE Atlantic surface water, which was reported to have been about 2.5 Bq m"3 in the same year [15]. It is interesting that caesium-137 was not detectable at Mitchelstown, probably because of dilution by freshwater from the River Foyie containing very low levels of caesium-137 (the Mitchelstown sampling point is beside the extended channel of the River Foyle). This is not unexpected, as it is well known that typical freshwaters are depleted in both stable caesium and radiocaesium relative to sea water. Caesium-134 concentrations were below the limits of detection at each of the three locations.
Total plutonium and americium concentrations in lough waters (Table 3) were between 2 and 3 orders of magnitude lower than those of caesium-137. Both diminished smoothly towards the entrance to the Lough, being 3 - 4 times lower at Magilligan Point compared to Culmore Point. These variations in plutonium and americium concentrations can be fully accounted for by the significant decrease in the suspended particulate loading, seaward of the Foyle Estuary.
Approximately 50% of the plutonium and 75% of the americium were associated with the particulate phase in lough water. This contrasts with the observations made in Carlingford Lough in 1990 [6], where the corresponding percentages were considerably smaller (Table 4). The difference is readily explained by the significantly higher suspended particulate loading of 4 - 20 mg 1"' in Lough Foyle, compared to 1-2 mg I'1 in Carlingford Lough, in part arising from the terrigenous input from the River Foyle. Overall, the concentrations of plutonium and americium in Lough Foyle were between 2 and 3 times lower than those measured in Carlingford Lough [6].
The Pu-238/Pu-239,240 activity ratios in filtered water and suspended particulate, at 0.18 ± 0.02 and 0.19 ± 0.06, respectively, are indistinguishable from one another. They are also consistent with the corresponding ratio in radioactive waste discharges into the Irish Sea from the spent fuel reprocessing plant at Sellafield, once account is taken of the effect of a small dilution by plutonium of global- fallout origin. This clearly indicates that the bulk of the, admittedly, small concentrations of plutonium detected in lough waters is sourced from Sellafield. Such an observation is in good accord with the well-established pattern of dispersal of radioactive waste from Sellafield through the waters of the North Channel and the Western Isles of Scotland. It confirms the results of an earlier study of the distribution of various radionuclides, including plutonium and americium, in inshore waters around the Irish coastline [7] which showed that the Islay sea front, located immediately to the north of the Inishowen Peninsula, effectively constrains the westward, though not the northward, penetration of radioactive effluent from Sellafield.
The Am-241/Pu-239,240 activity ratio in filtered water, at 0.37 ± 0.21, was significantly lower than on suspended particulate, namely 0.93 + 0.09, signifying the higher particle affinity/reactivity of americium. The proportion of plutonium in particulate form is highest at Culmore Point and reflects the significantly higher suspended load (19 mg I'1) measured near the River Foyle influx. The chemical speciation of plutonium was examined in samples of filtered lough water taken at Culmore Point and Redcastle. In both cases the bulk of the plutonium (90%) was in an oxidised form, i.e., Pu(V) (Table 4). This contrasts with the findings in Carlingford Lough [6], where most of the plutonium (-70%) was found to be in a reduced chemical form, i.e., Pu(IV). A likely explanation for this difference in behaviour is to be found in the respective proportions of plutonium present in a colloidal form in the two loughs. In Carlingford over 30% of the plutonium in the filtered fraction (< 0.45 nm) was in a colloidal form, compared to only 16% in Lough Foyle (Table 4). As plutonium in colloidal or pseudo-colloidal form is almost certainly in a reduced chemical form, it is evident that one should expect to find considerably less reduced plutonium in the waters of Lough Foyle. This, of course, is exactly what has been observed. Similar results to these have been reported for the western Irish Sea (9, '0, 11).
Sediment - water distribution coefficients (Kds), defined as the activity per unit mass of suspended paniculate (Bq kg'1, dry wt.) divided by the activity per unit mass of filtered water (Bq kg"1) under equilibrium conditions, have been deduced from the data for plutonium and americium, and are given
in Table 5. Total Kds for both elements differ by about an order of magnitude, the Kd for americium
being the larger, while the Kd for reduced plutonium is identical to that of americium. The similarity
between the Kds for Pu(IV) and americium is explained by the fact that americium is present in the water column almost exclusively in a reduced chemical form, as Am(III), and both Pu(IV) and Am(lII) have a near identical affinity for particulate matter. The order of magnitude difference
between the Kds for total plutonium and americium is due to the preponderance of Pu(V) in the 4 filtered water fraction which, having a Kd of about 10 , contributes significantly to a lowering of the
total plutonium Kd. Differences between the Kds measured in Lough Foyle and those in Carlingford Lough are largely attributable to the considerably higher percentages of plutonium and americium present in colloidal form in the latter zone.
Sediments
Radionuclide concentrations in estuarine sediments were determined on two samples collected 50 metres apart at each of 15 locations around the Lough (Tables 6 and 7). The caesium-137 concentrations were in the range of 1-54 Bq kg'1 and are significantly lower than those found along the north-east Irish coastline and in Carlingford Lough where they were in the range 8 - 200 Bq kg'1 [6].
Plutonium-238 and plutonium-239,240 concentrations were measured in nine sediment samples taken from the inter-tidal zone in Lough Foyle (Table 7). Concentrations ranged between 0.16 and 0.70 Bq kg'1 for plutonium-238 and between 0.53 and 4.16 Bq kg"1 for plutonium-239,240. In general these concentrations are lower than the corresponding caesium-137 concentrations and, on average, are a factor of two lower than the concentrations of these isotopes found in sediments from Carlingford Lough [6]. Sediments analysed from locations 50 m apart exhibited differences in concentrations which may be partially explained by differences in the particle sizes. The mean
10 plutonium-238/plutonium-239,240 ratio in the Lough Foyle sediments was 0.18 ± 0.05 and is typical of the ratio found in sediments in the western Irish Sea [10].
Particle-size distribution analysis was carried out on each of the 30 sediment samples (Table 8) and showed a weak trend of increasing caesium-137 concentration with increasing fine grain content (< 50 ixm, R2 = 0.57). This trend was found to be stronger for the isotopes of plutonium (< 50 /urn, R2 = 0.75) with admittedly fewer data points. However, an important perturbing factor in this analysis is the geographical variation in concentration of radionuclides. On examining individual sites such as Madams Bank, Coolkeeragh and Longfield, where there are significant differences in concentrations between samples taken from the same site, the sediment with the higher caesium-137 concentration also had a higher proportion of fine grains. A similar observation was made for the plutonium isotopes and their concentration in sediments was well correlated to those of caesium (R2 = 0.84). The analysis, therefore, supports the view that within sediment, caesium and plutonium are predominantly associated with fine particles rather than coarse material.
Biota
The radionuclide concentrations in the seaweed, Fuats vesiculosus, from Lough Foyle are given in Table 9. Concentrations in samples from six locations showed relatively little variation with good agreement between duplicate samples taken at each location. The mean caesium-137 concentrations of 0.9 Bq kg'1 (wet wt.) is lower than the mean value of 6.5 Bq kg*1 (wet wt.) found in Carlingford Lough and lower than the values reported along the Irish Sea coastline [2, 6, 16].
In the case of shellfish, the mean concentration of caesium-137 in mussels was 0.25 Bq kg'1 (wet wt.) (Table 10), which is lower than the value of 1.3 Bq kg"1 (wet wt.) found in mussels in Carlingford Lough [6]. The caesium-137 concentration in winkles and the caesium-134 in both mussels and winkles were below the levels of detection. The mean concentrations of plutonium-239,240 in the two species were 0.036 Bq kg'1 (wet wt.) and 0.017 Bq kg'1 (wet wt.), respectively (Table 11) and are lower than the concentrations of 0.118 Bq kg'1 (wet wt.) and 0.120 Bq kg'1 (wet wt.) measured in mussels and winkles from Carlingford Lough [6].
Gamma Dose-Rate Measurements
The gamma dose-rates in air measured at 17 inter-tidal sites around the Lough are given in Table 12. The overall mean was 70 ± 9 nGy h'1, slightly lower than the mean value of 96 ± 10 nGy h"' reported for Carlingford Lough [6]. The highest values were found over the muds and silts of Culmore Point and Madams Bank, where the values were 85 and 87 nGy h"1, respectively.
11 5 RADIOLOGICAL ASSESSMENT
Using the data obtained in this study, an assessment of dose from seafood consumption and recreational use can be made. A convenient method for estimating the radiological consequences of the measured concentrations of radioactivity in the environment :s by reference to the generalised derived limits published by the National Radiological Protection Board (NRPB) [17]. These generalised derived limits are concentrations in environmental media which might lead to an annual dose of 1 miJJisievert to an individual. This is the recommended International Commission on Radiological Protection (ICRP) dose limit for members of the public. Deliberately cautious assumptions are made in calculating them so that their application is not likely to underestimate the dose. The NRPB recommend that if environmental levels exceed 25% of the generalised derived limits further investigations should be undertaken so that site-specific parameters can be used in the dose calculation.
Table 13 sets out the highest concentration found in each medium sampled and expresses it as a percentage of the generalised derived limit. The highest percentage in marine samples corresponds to caesium-137 in beach sediment which, at 0.8%, is well below the 25% investigation threshold.
A second approach to the estimation of dose in the absence of a habits survey is to postulate a hypothetical individual who lives close to the shoreline, utilises the lough extensively for recreational and work purposes and consumes large quantities of locally caught seafood. If it is assumed that he spends 100 hours/year swimming, 1,000 hours/year on the inter-tidal areas and ingests 10 g of sand a year, he would receive a dose of less than 1 microsievert in a year from these activities. External irradiation from caesium-137 in beach sediment is the primary contributor to this dose. In addition, if the same individual consumed 50 kg fish, 10 kg crustaceans and 10 kg molluscs in a year, he would receive an additional dose in the order of 1 to 2 microsieverts. While no fish samples were analysed during this study, published concentration factors (water to fish) for caesium-137 were employed to estimate representative caesium-137 concentrations in fish in Lough Foyle. These concentrations were then used in the estimation of dose.
It is clear that this hypothetical individual, who is not typical, receives a dose of less than 5 microsieverts in a year from artificial radionuclides, i.e., less than 0.5% of the ICRP limit of 1,000 microsieverts, from the pathways considered. This is very small when compared with the annual average dose of approximately 3,000 microsieverts received by members of the Irish public from natural sources of radiation. It is, therefore, concluded that the dose resulting from artificial radioactivity in Lough Foyle is of negligible radiological significance.
6 CONCLUSIONS
Although traces of plutonium, americium and radiocaesium from Sellafield are detectable in Lough
12 Foyle, the concentrations in various marine media are significantly lower than those found along the NE coast of Ireland and in the western Irish Sea.
Comparison with representative global fallout concentrations in the NE Atlantic would indicate that at least 70% of the, admittedly, minute inventories of plutonium, americium and radiocaesium within the waters of the Lough can be attributed to past discharges from Sellafield.
Most of the plutonium in filtered sea water was found to be in a soluble form, in agreement with observations made elsewhere throughout the NE Atlantic and the Irish Sea. Much, if not all, of the remainder appeared to be in colloidal form. The distribution of plutonium and americium between sediment and sea water in the Lough was similar to that observed throughout the Irish Sea in the course of other studies. There is evidence to support the view that within sediment, caesium and plutonium are predominantly associated with the fine particle (<50 /xm) fraction.
Ambient gamma dose-rates over inter-tidal sediments in the Lough are slightly lower than those found in a similar survey in Carlingford Lough in 1990. These dose rates are predominantly of natural origin.
The minute quantities of artificial radioactivity found in Lough Foyle are of negligible radiological significance.
7 ACKNOWLEDGEMENTS
Industrial Research and Technology Unit (Department of Economic Development), Lisburn, for their measurement of the particle-size distribution of the sediment samples.
13 REFERENCES
1. Directorate of Fisheries Research, Radioactivity in Surface and Coastal Waters of the British Isles in 1993. MAFF, Lowestoft, 1994.
2. McGarry, A., Lyons, S., McEnri, C, Ryan, T., O'Colmain, M. and Cunningham, J.D., Radioactivity Monitoring of the Irish Marine Environment 1991-92. Radiological Protection Institute of Ireland, Dublin, 1994, 38 pp.
3. O'Grady, J., Currivan, L., McEnri, C, O'Colmain, M., Colgan, P.A. and Cunningham, J.D., Radioactivity Monitoring of the Irish Marine Environment 1988-90. Nuclear Energy Board, Dublin, 1990, 28 pp.
4. O'Grady, J. and Currivan, L., Radioactivity Monitoring of the Irish Marine Environment 1987. Nuclear Energy Board, Dublin, 1990, 28 pp.
5. Department of the Environment, Northern Ireland. Report of the Chief Alkali Inspector for the years 1992-1993. HMSO, Belfast, 1994.
6. Mitchell, P.I., Vives Batlle, J., Ryan, T.P., McEnri, C, Long, S., O'Colmain, M., , Cunningham, J.D., Caulfield, J.J., Lannour, R.A. and Ledgerwood, F.K., Artificial Radioactivity in Carlingford Lough. Radiological Protection Institute of Ireland, Dublin, 1992, 37 pp.
7. Mitchell, P.I., Sanchez-Cabeza, J.A., Vidal-Quadras, A. and Font, J.L., Distribution of plutonium in inshore waters around Ireland using Fucus vesiculosus as a bio-indicator. In: Proc. CEC/CIEMAT Seminar on the Cycling of Long-Llved Radionuclides in the Biosphere: Observations and Models, Madrid, 15-19 September 1986, Commission of the European Communities, Luxembourg, 1987, vol. II, 13 pp.
8. Crowley, M., Mitchell, P.I., O'Grady, J., Vives i Batlle, J., Sanchez-Cabeza, J.A., Vidal- Quadras, A. and Ryan, T.P., Radiocaesium and plutonium concentrations in Mytilus edulis (L.) and potential dose implications for Irish critical groups. Ocean and Shoreline Management, 1990, 13, 149-161.
9. Mitchell, P.I., Vives i Batlle, J., O'Grady, J., Sanchez-Cabeza, J.A. and Vidal-Quadras, A., Critical group doses arising from the consumption of fish and shellfish from the Western Irish Sea, In: New Developments in Fundamental and Applied Radiobiology, C. B. Seymour and C. Mothersill (Eds.), Taylor and Francis, London, 1991, Chapter 10, pp. 381-390.
14 10. Mitchell, P.I., Vives i Batlle, J., Ryan, T.P., Schell, W.R., Sanchez-Cabeza, J.A. and Vidal- Quadras, A., Studies on the speciation of plutonium and americium in the Western Irish Sea. In: Radionuclides in the Study of Marine Processes, P.J. Kershaw and D.S. Woodhead (Eds.), Elsevier Applied Science, London and New York , 1991, pp, 37-51.
11. Mitchell, P.I., Vives i Batlle, J., Downes, A.B., Condren, O.M., LeonVintro, L. and Sanchez- Cabeza, J.A., Recent observations on the physico-chemical speciation of plutonium in the Irish Sea and the Western Mediterranean. J. Appl. Radiat. Isot., 1995, 46, 1175-1190.
12. Lovett, M.B. and Nelson, D.M., Determination of some oxidation states of plutonium in sea water and associated particulate matter. In: Proc. Symp. Techniques for Identifying Transuranic Speciation in Aquatic Environments, Ispra, Italy, 1980, IAEA, Vienna (STI/PUB/613), 1981, pp. 27-35.
13. Nevissi, A. and Schell, W.R., Distribution of plutonium and americium in Bikini Atoll Lagoon. Health Phys., 1975, 28, 539-547.
14. Nevissi, A. and Schell, W.R., Efficiency of a large volume water sampler for some radionuclides in salt and freshwater. In: Radioecology and Energy Resources, J.E. Cushing Jr. (Ed.), Dowden, Hutchinson and Ross, Stroudsburg, Pennsylvania, 1976, pp. 277-282.
15. Dahlgaard, H., Chen, Q., Herrmann, J., Nies, H., Ibbett, R.D. and Kershaw, P.J., On the background level of technetium-99, strontium-90 and caesium-137 in the North Atlantic. J. Mar. Systems, 1995, 6, 571-578.
16. Garland, J.A., McKay, W.A., Burton, P.J. and Cambray, R.S., Studies of environmental radioactivity on the coasts of Northern Ireland. Nucl. Energy, 1990, 29, No. 3, 205-223.
17. National Radiological Protection Board. Revised Generalised Derived Limits for Radioisotopes of Strontium, Iodine, Caesium, Plutonium, Americium and Curium. NRPB-GS8, HMSO, London, 1987, 56 pp.
15 TABLE 1 Location of sampling sites in Lough Foyle
Location Grid Reference Samples Collected Co Donegal
Dunagrcc Point C683 427 Sediment, seaweed, sea water Movillc C611 380 Sediment, seaweed, mussels Rcdcastlc C557 348 Sea water Drung C541 340 Sediment Lepers Point C503 287 Sediment, seaweed Mitchclstown C489 268 Sediment, winkles, mussels, sea water
Co Londonderry Culmore Point C470 222 Sediment, seaweed, sea water Madams Bank C451 192 Sediment Coolkceragh C482 222 Sediment, seaweed Donnybrewer C524 242 Sediment, seaweed, sea water, winkles Longfield C549 223 Sediment Faughanvale C583 224 Sediment, mussels Carrichu C601 228 Sediment, mussels Bally macran C629 263 Sediment Balls Point C645 304 Sediment Magilligan Point C658 387 Sea water Benone C720 361 Sediment
16 TABLE 2
Radiocaesiuni in filtered sea water at shoreline stations in Lough Foyle
Locution Concentration (Ilq mJ)
Cs-134 Cs-137
Dunngree Point 8± 1
Milchelsunvn <2
Dunnybrewer 12 ± I
Uncertainties quoted arc ± 1 S.D,
TABLE 3
Plutonium and amcricium in sea water in Lough Foyle and Carlingford Lough
Locution Fraction Concentration (niBq Pu-238/ Am-241/ Pu-239,240 Pu-239,240 I'u-238 Pu-239,240 Am-241
Culmore Paniculate 13.4 ± 0.9 81 ± 3 66 ± 5 0.17 ± 0.01 0.82 ± 0.07
Point Fillnite 8.6 ± 0.8 35 ± 2 21 ± 2 0.25 ± 0.03 0.61 ± 0.07
Total 22.0 ± 1.2 116 ± 3 87 ± 5 0.19 ± 0.01 0.75 ± 0.05
* Redcastle Particuliilu 5.1 ± 0.5 25.3 ± 1.3 25 ± 3 0.20 ± 0.02 0.98 ±0.13
Filtrate 3.7 ± 0.4 25.6 ± 1.4 7.1 ± 1.8 0.14 ± 0.05 0.28 ± 0.07
Total 8.8 ± 0.6 50.9 ± 1,9 32 ± 3 0.17 ± 0.03 0.62 ± 0.07
Magilligan Paniculate 2.4 ± 0.2 13.7 ± 0.6 13.4 ± 1.2 0.17 ± 0.02 0.98 ± 0.10
Point Filtrate 4.1 ± 0.4 22.9 ± 1.0 4.7 ± 2.3 0.18 ± 0.02 0.21 ± 0.10
Total 6.5 ± 0.4 36.6 ± 1.2 18.1 ± 2.6 0.18 ±0.01 0.49 ± 0.07
Mean Paniculate 7 ±6 40 ± 36 35 ± 28 0.18 ± 0.02 0.93 ± 0.09
(n=3) Filtrate 5 ±3 28 ± 6 11 ± 9 0.19 ± 0.06 0.37 ± 0.21
Total 12 ± 8 68 ± 42 46 ± 36 0.18 ± 0.01 0.62 ± 0.13
Carlingford Paniculate 11 ±2 48 ± 10 19 ± 3 0,23 ± 0,01 0.40 ± 0,09
Lough Filimre 41 ± / 200 ± 16 71 ± 6 0.21 ± 0.02 0.36 ± 0.06
Total 52 ± 1 248 ± 14 90 ± 4 0.24 ± 0.02 0.36 ± 0.07
Uncertainties quoted are ± I S.D.
17 TABLE 4
Physico-chemical speciation of plutonium and americium in sea water in Lough Foyle, (Carlingford Lough and the Western Irish Sea)
Locution Suspended % on suspended piirticulnte % Pu(V) % Colloidnl LoillJ in filtrate I'u in filtnitc (mg I'1) Pu-23!),240 Am-241 Culmore Point 19 ± 1 70 ± 3 76 ± 7 87 ± 18 8 ±4 Kcdcastlc 5 ± 1 50 ±3 78 ± 12 93 ± 14 23 ±7 Magilligan Point 4 ± 1 37 ±4 74 ± 13 NM NM Mean (n=3) - 52 ± 17 76 ±2 W ± 4 16 ± 11
Carlingford Lough 1-3 19 ±2 21 ±4 30 ± 15 31 ±6 Western Irish Sea 1-2 21 ±5 56 ± 21 S3 ±7 15 ±3
Uncertainties quoted are ± 1I.S.D. NM = Not measured
TABLE 5
Sediment-water distribution coefficients (Kds) for plutonium and americium in Lough Foyle, (Carlingford Lough and the Western Irish Sea)
K,, (total) K,, (reduced) Location Pu-239,240 Am-241 Pu-239,240(IV)
Culmore Point (1.2 ±0.1). 10' (0.16 ±0.02). 10" (I.I ±0.1).I0s
Redcastle (2.2 ± 0.2). 10' (0.8 ± 0.2). 10" (2.6 ± 0.4).10"
Magilligan Point (1.5 ±0.1).10' (0.7 ±0.3). 10" NM •
Mean (n=3) (1.6 ±0.5).10' (0.6 ± 0.3). 10" (1,9 ± 1.0).10"
Carlingford Lough (2.1 ± 0.4). 10" (2.3 ± 0.6).10< (3 ± l).10<
% Western Irish Sea (5 ± 3).10> (5 ± 3). 10' (6 ±4).10
Uncertainties quoted are ± 1 S.D. NM = Not measured
18 TABLE 6
Radiocacsium in sediment in Lough Foyle
Location Sample Concentration (Bq kg"1, dry wt.)
Cs-134 Cs-137
Madams Bank A 0.8 ± 0,1 22,7 ± 0.5
B 2.3 ± 0.3 54.0 ± 1.4
Culmore Point A 0.4 ± 0.1 13.2 ± 0.4
B <0,3 14.4 ± 0.4
Mitchelstown A <0.3 11.5 ± 0.5
B 0.4 ± 0.1 11.8 ± 0.4
Lepers Point A 0.4 ± 0.1 17.3 ± 0.4
B 0.3 ± 0.1 15.2 ± 0,5
Drang A <0.4 11.4 ±0.5
B <0.2 15.8 ± 0,5
Moville A <0.1 1.8 ± 0.1
B <0.1 1.7 ± 0.1
Dunagree Point A <0.1 1.8 ± 0.1
B <0.1 1.8 ± 0.1
Coolkeeragh A <0.2 1.7 ±0.2
B 1.0 ± 0,1 32.7 ± 0.8
Donnybrcwcr A 1.0 ±0.1 4.2 ± 0.2
B <0,2 3.6 ± 0.2
Long field A <0,l 7,2 ± 0.2
B 0.4 ± 0.1 31.3 ±0.8
Fauglianvale A <0.4 17.0 ± 0.5
B 0.3 ± 0.1 11.9 ± 0.3
Carrichu A <0.3 4.7 ± 0.3
B <0.2 4.7 ± 0.3
Ballymacran A <0.3 8.5 ± 0.4
B <0.1 7.4 ± 0.3
Balls Point A <0,2 4.8 ± 0.2
B <0.1 3.7 ± 0.2
Benone A <0.1 1.0 ± 0.1
B <0.1 1.0 ± 0.1
Mean <0.4 11 ± 12
Uncertainties quoted are ± l.S.D.
19 TABLE 7
Plutonium and amcricium in sediment in Lough Foyle
Locution Sample Concentration (!!([ kg'1, dry wt.) Pn-238/ Am-241/ Pu-239,240 Pu-239,240 I'u-238 I'u-239,240 Am-241
Madams Bunk A 0.36 ± 0.01 2.13 ±0.03 2.7 ±0.1 0.169 ± 0,003 2.71 ± 0.20
B 0.70 ± 0.01 4.16 ± 0.05 5.9 ± 0.3 0,168 ±0.003 1.42 ± 0,16
Lepers Point 0.36 ± 0.02 2.00 ± 0,04 NM 0,18 ± 0,01 NM
Drung 0.49 ± 0.01 2,93 ± 0.04 NM 0.167 ± 0.004 NM
Coolkecrngh A 0.16 ±0.01 0.53 ± 0.01 0.8 ±0.1 0,30 ± 0.01 1.57 ± 0.10 B 0.50 ± 0.01 2.86 ± 0.04 NM 0.175 ± 0.005 NM
Longficld A 0,26 ± 0.02 1.32 ± 0.04 NM O.20 ± 0.031 NM B 0.50 ± 0.02 3.38 ± 0.05 NM 0.15 ± 0.01 NM
Ballymacran 0,25 ± 0.0! 1.57 ± 0.03 2.1 ± 0.1 0.16 ± 0.01 1.31 ± 0.08
Mean - 0.40 ± 0.17 2.3 ± 1.1 2.9 ± 2.2 0.19 ± 0.05 1.8 ± 0.6
Uncertainties quoted ar« ± 1 S.D. NM = Nut measured
20 TABLE 8
Particle-size distribution of sediments in Lough Foyle
Location Sample Percentage in particle-size Range (jim)
>2000 2000-500 500-250 250-125 125-50 50-20 20-2 <2
Madams Bank A 22.4 8.4 8.0 17.2 9.2 17.0 17.1 0.7
B 1.5 2.6 3.6 12.0 15.9 34,9 28.9 0.6
Culmore Pt. A 18.7 10.4 14.2 34.6 6.5 6.8 8.0 0.8
B 7.4 2,0 3.4 43.9 8.8 18,5 15.4 0,6
Mitchelstown A 10.6 5.6 23.0 44.2 5.3 5.6 5.1 0.6
B 0.3 1.1 10.9 58.9 10.9 10.3 7.1 0.5
Lepers Point A 0 0.3 2.0 10.0 49.7 25.9 11.8 0.3
B 0 0,2 0.8 6.3 56.9 24.4 11.1 0.3
Dning A 0.1 0.3 0.9 24.2 50.0 15.4 8.8 0.3
B 0.1 0.8 4.3 15.2 47.1 23.1 9.2 0.2
Moville A 0 0 25.6 73.0 0.1 0 0.1 1.2
B 0 0.2 33.8 64.9 0.6 0.1 0.1 0.3
Dunagrce Point A 0 0.3 17.4 80.9 0.8 0.1 0.1 0.4
B 0 0,5 34.4 64.4 0.4 0 0 0.3
Coolkeeragh A 3.3 2.2 68.9 25.1 0.1 0.1 0.1 0.3
B 0.3 0.6 2.0 58.4 14.3 14.2 9.8 0.4
Donnybrewer A 0.7 7.0 20.0 65.8 2.7 1.9 1.5 0.4
B 0.2 2.2 18.9 74.2 2.5 0.8 0.8 0.4
Longficld A 0.3 1.0 2.8 64.2 17.7 7.5 6.1 0.4
B 0.4 l.l 1.0 21.4 20.5 29.8 25.3 0.5
Paugliiinvale A 8.1 16.4 19.9 21.1 14.2 12.3 7.6 0.4 B 5.5 30.0 30.1 18.2 3.2 0.8 5.6 0.6
Carricliu A 1.0 2.3 4.6 33.9 21.8 20.0 15.7 0.7
B 0.4 0.7 5.1 32.5 17.3 21.3 21.8 0.9
Ballymacran A 0.5 5.2 16.5 29.6 12.9 14.5 19.7 1.1
B 2.0 4.7 46.0 16.9 12.3 9.6 8.0 0.5
Balls Point A 0.1 0.8 8.0 88.6 2.6 0.6 0.9 0.4
B O.i 0.7 8.9 87.0 2.2 0.4 0.4 0.3
Benune A 0 0.4 8,6 88,8 1.4 0.3 0.1 0.4
B 0 0.3 15.0 82.8 1.2 0.2 0.2 0.3
21 TABLE 9
Radiocaesium in Fucus vesiculosus in Lough Foyle
Location Sample Concentration (Bq kg'1, wet wt.)
Cs-134 Cs-137
Culmore Pt. A <0,09 2.5 ± 0,2 B <0.14 2.2 ± 0.3
Lepers Point A <0.06 1.0 ± 0.8 B <0.08 0.9 ± 0,2
Moville A <0.09 0.4 ± 0.1 B <0.07 0.4 ± 0.1
Duiiagrce Pi A <0.07 0.4 ± 0.1 B <0.06 0.3 ±0,1
Donnybrewer A <0.08 0.5 ± 0,1 B <0.U 1.0 ±0.1
Coolkeeragh A <0.05 0.9 ± 0,1 B <0.13 1.2 ± 0.2
Mean <0.08 1.0 ±0.8
Uncertainties quoted are ± 1 S.D,
TABLE 10
Radiocaesium in mussels and winkles in Lough Foyle
Location Concentration (Bq kg"1, wet wt.)
Cs-134 Cs-137
Mussels
Moville <0.06 0.14 ± 0.03
Fuaghanvale <0.06 0.32 ± 0.04
Carrichu <0.07 0.28 ± 0.04
Mitchelstown <0.07 0.24 ± 0,04
Mean <0.07 0.25 ± 0.08
Winkles
Donnybrewer <0.14 <0.15
Mitclielstown <0.16 <0.18
Mean <0.15 <0.17
Uncertainties quoieil are ± 1 S.D,
22 TABLE 11
Plutonium and americium in mussels and winkles in Lough Foyle
Concentration (Ilq kg'1, wet wt.) Pu-238/ Pu-239,240 Location Pu-238 Pu-239,240 Am-241
Mussels
Moville 0.002 ±0.001 0.016 ± O.O01 0.013 ± 0.001 0.13 Faughanvale NM 0.022 ± 0.001 0.065 ± 0.002 NM
Ciirrichu 0.010 ± 0.001 0.041 ± 0.002 0.058 ± 0.002 0.24
Mitchelstown 0.010 ± 0.002 0.065 ± 0.004 0.048 ± 0.002 0.16
Mean 0.007 ± 0.005 0.04. ± 0.02 0.05 ± 0,02 0,18
Winkles
Donnybrewer 0.003 ± 0,001 0.022 ± 0.003 0.038 ± 0.002 0.14
Mitchelstown 0.005 ± 0.001 0.011 ±0.001 0.024 ± 0.001 0,45
Mean 0.004 ± 0.001 0.017 ± 0.008 0.03 ± 0,01 0.30
NM = Not measured Uncertainties quoted are ± 1 S.D.
TABLE 12
Gamma dose-rate measurements at inter-tidal sites around Lough Foyle
Location Site description Gamma dose-rate in air at 1 m (nGy h'1)
Castlerock Sandy 59 Benone Sandy 59 Balls Point Sandy 62 Carrichu Silt Mud 72 Donnybrewer Sandy/Silt 72 Coolkceragh Sandy/Silt 73 Longfield Sandy/Silt 67 Faughanvale Mud 71 Ballymacran Mud 64 Culmore Point Silt/Mud 85 Madams Bank Silt/Mud 87 Lepers Point Sandy 88 Drung Shingle/Sand 73 Mitchelstown Shingle 69 Moville Sandy 72 Greencastlc Sandy 57 Dunagree Point Sandy 63
Mean (n = 17) 70 + 9
23 TABLE 13
Maximum levels of radionuclides in Lough Foyle in comparison with generalised derived limits
Sample Unit Radionuclide Maximum Generalised Percentage concentration Derived oi" GDL Limit (GDL)
Filtered seawater Bq I"I1 Cs-137 1.22 x 10-2 2 0.61 Pu-239,240 3.5 x 10s 0.03 0.12
Am-241 2.1 x 105 0.005 0.44
Bq kg"1 (dry wt.) Cs-137 54 7x 10J 0.77
Pu-239,240 4.16 4x 104 0.01
Am-241 5.89 3x 10* 0.0196
Molluscs Bq kg"1 (wet wt.) Cs-137 0.32 1 x 104 0.0032 Pu-239,240 0.065 2x 102 0.0325
Am-241 0.065 I x 102 0.065
24