Tile Science of the Total Environment, 105 (1991 ) 211-23 I Elsevier Science Publishers B.V., Amsterdam

211

Radioactivity in environmental samples taken in the Sellafield, Ravenglass and Morecambe Bay areas of west Cumbria E.J.C. Curtis a, D.S. Popplewell b and G.J. Ham b ~Ministry of Agriculture, Fisheries and Food, ~ood Sci'.'nce Divisitm, Ergon House, :'/o Nobel House, 17 Smith Square, London SEIP 3JR, United Kingdmn bNational Radiological Protection Board, Chilton, Didcot. Oxon OXI! ORQ, United Kingdom (Received July 19th, 1990; accepted August 31st, 1990)

ABSTRACT Seaborne sediments deposited in the estuaries of the Esk, Duddon, Leven and Kent have been analysed fc,r fission products and actinides discharged in waste from the Sellafield processing works in west Cumbria, and the values ccmpared with the generally expected values due to fallout from atmospheric nuclear weapons tests. Analyses of tissues from sheep grazing the marshes of these estuaries show that the internal radiation dose of the general public through eating mutton or liver from these animals would be at most a few percent of recommended limits. Analytical data are presented on the actinide content of beef cattle, and on potato crops grown under field conditions; these data show that, as with the sheep data, the radiation dose to the consumer would be small.

~NTROI) UC'i |ON

In 1977 the Ministry of Agriculture, Fisheries and Food commenced a programme of monitoring artificial radionuclides in the terrestrial environment close to the British Nuclear Fuels pie reprocessing plant at Sellafield, and in the region commonly known as the Ravenglass estuary. Results of this study obtained between 1977 and 1982 were summarised in a previous publication [1]. It was concluded that the internal irradiation of consumers of locally produced food amounted to no more than a small fraction of the recommended limits. In subsequent years the work was extended to take in the sampling of soil cores and sheep from the shores of the Duddon estuary and Morecambe Bay, areas that had not been studied in the earlier programme. Grass and milk sampling continued after 1982, and the results have been reported [2]. This paper reports the results produced from 1982 up to 1986, the year of the Chernobyl accident. For the sake of completeness we include some

E.J.C. CURTISET AL.

212

• Workington ~l,$carn~s

\

Lake

~R.Duddon

~__. km , : ~ ; f Walney'~"~

J

Morecam~

Fig. !. The Sellatield, Ravenglass and Morcambe Bay areas of west Cumbria

of the results from sites sampled continually since 1977 and presented in the 1984 paper [1]. MATERIALS AND METHODS

The methods of collecting and analysing the samples have been described previously [1]. A map of the region is shown in Fig. 1. Sites 1-12 of this study (Tables 1-4) are the Sites 1-12 of the previous study [1]. Sites I-4 were within a zone of radius approximately 1.5 km centered on Sellafield Works, Sites 5-7 were within an annular zone of radii between 2 and 3.5 km centered on Raven#ass, and the control Sites 8-12 are shown in Fig. 1. Sites 13 and above were new sites and are situated in the estuaries of the Esk, Duddon, Leven, and Kern. Additional information is given in footnotes to the appropriate tables. RESULTS A N D DISCUSSION

Soil and root mat samples

Radionuclide distributions for rootmat plus soil from the sites that were sa,npled year by year are shown in Tables 1-4. The designation root mat plus soil refers to a soil core of approximately 150 mm depth. The greatest uncer-

172 101 120 ! 04 101

8, 9, 10, 1 I, 12,

177 95 103 82 ! I0

316 332 13800

2020 1730 10650 1530

July i980

235 158 125 107 119

236 290 10600

2360 2580 10100 1470

Sept. 1981

238 145 64 98 ! 32

546 !!7 520

1460 2360 8250 730

Aug. 1982

250 150 250 i 70 170

210

440 27000

1600

2070 370 250 50400

3600 3500

Sept. 1984

2350 2870

Sept. 1983

(400)

300 23000

1300

2700 2900

Sept. 1985

4. ± 4. 4-

300 200 530 150

214 130 i 32 I !2 126

± 4+ + +

14 13 3I 15 12

410 4. 80 290 4. 30 b

2590 2600 9780 1430

Mean 4- SEM

a Sites 1-4 were within the SeUafield Works zone, Sites 5-7 were in the Ravenglass region, and Sites 8-12 were controls; see text. b The radioactivity at Site 7 depended on recent tidal conditions, and deposition or removal of silt was variable so that a mean value may not be representative. It is unlikely that the corer reached the full dep(h of radionuclide deposition.

564 275 15700

5 6 7

Eskdale Near Dean Silecroft Scarness SE of Uiverston

3630 2290 10100 1320

July-Aug. 1979

1 2 3 4

Site a

Plutonium-239 + 24°Pu in mat plus soil (Bq m -:)

TABLE I

N

t~

58 46

318 241 ! 3400

646 (188) 1540 201

July 1980

81 60 76 53 43

193 278 ! 5000

986 688 2400 759

Sept. 1981

66 61 96 81 44

972 373 539

1000 648 2100 517

Aug. 1982

69 (130) 55 98 (420)

75

440 33000

380

450 210 (80) 47000

1200 710

Sept. 1984

1040 590

Sept. 1983

500 39000

600

1200 800

Sept. 1985

4444.

75 50 250 70

70 50 68 65 44

4. 4. 4. 4. +

4 6 12 14 1

440 4. 140 340 +_ 50 b

1040 640 1840 460

Mean 4- SEM

a

Sites !-4 were within the SeUafield works zone, Sites 5-7 were in the Ravenglass region, and Sites 8-12 were controls; see text. bThe radioactivity at Site 7 depended on recent tidal conditions, and deposition or removal of silt was variable so that a mean value may not be representative. It is unlikely that the corer reached the full depth of radionuclide deposition.

34 43 29 44

528 185

5 6 7

8, Eskdale 9, Near Dean 10, Silecroft 11, Scarness 12, SW of Ulverston

1190 423 1330 323

July-Aug. 1979

1 2 3 4

Site a

Americium-241 in mat plus soil (Bqm -2)

TABLE 2

7520 14300 2670 1550 1960 8700

2 3 4

5 6 7

1979

2750 1710 1090 1970 1540

1200 1440 7970

4580 14500 2750

3120

July 1980

2860 2310 1540 2370 2490

1100 1450 26600

5420 21100 3100

3540

Sept. 1981

2000 1890 760 1800 1620

1183 1740 1700

5810 13100 2650

3440

Aug. 1982

2200 1800 990 1600 1700

1040 1150 13OOO

2820

4500

3020

Sept. 1983

2530 1920 1180 1910 1900

f f t * f

h

18tj IO0 IS0 130 180

1210 2 200 ISSO f 14n

s570 + 550 15750 f 1810 2800 f 80

34Oo-r_160

Mean 3: SEM

“Sites l-4 were within the Sellafield works zone, Sites 5-7 were in the Ravenglass region, and Sites 8-12 were conlrols; see text. bThe radioactivity at Site 7 depended on recent tidal conditions, and deposition or removal of silt was variable so that a mean value may not be representative. It is unlikely that the corer reached the full depth of radionuclide deposition.

2820 1870 1540 1790 2060

3900

1

8, Eskdale 9, Near Dean IO, Silecroft 11, Scarness 12, SW of Ulverston

July-Aug.

in mat plus soil (I34r1~-~)

Site a

Strontium-90

TABLE 3

g 9 3 B

2 z x 9

9930 18500 41600 lllO0

15000 11300 43900

6820 5580 5110 4340 7050

1 2 3 4

5 6 7

8, 9, 10, 1I, 12,

7020 4950 4640 4050 6250

14000 11800 30400

9910 15800 50800 !0900

July 1980

6860 4260 4540 3640 5960

11300 8410 171000

10400 18300 53400 llO00

Sept. 1981

6130 4060 4210 3850 5170

13000 IIOG0 5370

10300 18100 49800 llO00

Aug. 1982

7400 4500 4700 4700 5800

6800

8600 56000

llO00

14700 18700 11300 36500

11000 16000

Sept. 1984

15200 12100

Sept. 1983

9000

(5000) 68000

13000

!!000 18000

Sept. 1985

± ± ± ±

700 900 2500 600

7150 4670 4640 4120 6050

+ 340 _ 600 -I- 140 + 190 _.+ 300

14400 ± 4200 10400 ± 600 b

!!!00 16700 48900 ll800

Mean ± SEM

"Sites I--4 were within the Sellafield works zone, Sites 5-7 were in the Ravenglass region, and Sites 8-12 were controls; see text. bThe radioactivity at Site 7 depended on recent tidal conditions, and deposition or removal of silt was variable so that a mean value may not be representative. It is unlikely that the corer reached the full depth of radionuclide deposition.

Eskdale Near Dean Silecroft Scarness SW of Ulverston

July-Aug. 1979

Site a

Caesium-137 in mat plus soil (Bqm -z)

TABLE 4

t,J

RADIOACTIVITY IN ENVIRONMENTAL SAMPLES

217

tainty in a particular sample is in the reproducibility of taking and preparing the sample for analysis. Therefore the uncertainties of the analyses, which would be reflected in the counting uncertainties, are not shown in the tables because they would give an unjustifiable impression of an overall low uncertainty. Within the group of control sites, Site 8 had consistently the greatest radionuclide deposits per unit area. The explanation for this lies in the increased rainfall at the site. Table 5 shows Meteorological Office data [3] from Rainfall Stations closest to the radionuclide sampling sites. From the Rainfall Station data, estimates were made of the rainfall at the radioactivity sampling sites, recognising that there could be inaccuracie~,~ in the procedure because appreciable differences of rainfall are possible over quite small distances due to the differences in altitude and aspect of the rainfall measurement points. As far as possible the Rainfall Stations and the radionuclide sampling sites were reasonably close, and had similar altitudes and aspects. Certain Rainfall Stations had data only over a limited period, whereas others had data covering a period of over 30 years. However, Meteorological Office data [3] show that the rainfall data over the period 1980-86 were not markedly out of line with the 1941-70 figures. Using the Rainfall Station data of Table 5, the rainfall at each of the control radionuclide sampling sites was estimated as shown in Table 6 column 2. Using the estimated rainfall at the control sites, the radionuclide data from the control Sites 8-12 shown in Tables 1, 2 and 4 were normalised to a rainfall of 1000 mm per year (Table 6, columns 3-5). The 9°Sr data were rather variable, giving an average deposition of about 1250 Bqm -2 per 1000 mm rainfall. However, the depth of the cores, about 15cm, was probably insufficient to sample the full depth of the soil penetration by the more mobile 9°Sr, consequently the '~°Sr activities per unit area (Table 3) are probably underestimates. The control sites show an approximately constant radionuclide deposition per unit area per 1000 mm rainfall, though there are variations, for example 239pu q- 24°pu at Site 11 (Table 1) and 137Cs at Site 12 (Table 4). For the Sellafield and Ravenglass zones the deposition is generally greater than that at the control sites and is unrelated to the amount of rainfall. Meteorological Office data [3] show that the average annual rainfalls at the Windscale Works and Eskmeals Rainfall Stations are amongst the lowest for the region at about 1080mm. Bearing in mind the uncertainties in assessing the rainfall at the control sites, the normalised radionuclide deposition figures agree reasonably well with previously published fallout data. Bennett [4] published fallout plutonium results for New York which convert to a present-day value of approximately 100Bqm -2 per 1000mm rainfall. Krey ,:t al. [5] reported that the 24IAm fallout content of soil was about 255~ of the 239pu + 24°pu, and this proportion would peak in about the yea~ 2037 at 42% based on predictive

Altitude (m)

30 115 25

85 85

Rad~onuchde sampling site

8, Eskdale 9, Near Dean 10, Silecrofl

11, Scarness 12, S W o f Ulverston

NY 217307 SD263771

NY 155002 NY 074255 SD132823

OS Grid reference NY 195011 NY 067250 SD 165851 NY 246243 SD264738 SD246724 SD240781

76 40 67 156

How Farm Little Urswick Stainton Poaka Beck

OS Grid reference

85 91 44

Altitude (m)

Boot Dean S. Works Lanthwaite

Met. Office Rainfall Station

Annual rainfall at Meteorological Office Rainfall Stations close to the radionuclide sampling sites

TABLE 5

Rainfall period 1980-86 1980-82 1941-70 198fi-86 1980-86 1941-70 1980-82 1980-86 1941-70 1980-86

Rainfall (mmyear -I) 1983 1338 1399 1466 1563 1195 1440 1252 1305 1403

Oo

t~

1980 1340 1400 1560 1270

8, 9, 10, 11, 12,

Eskdale Near Dean Silecroft Scarness SW of Ulverston

Annual estimated rainfall (mm)

Site

Mean ± SEM

3610 3480 3310 2640 4760 3560 ± 340

35 ~7 49 42 35 40± 3

108 97 94 72 99 96±6

137CS 24nAm

239Pu + 24oPu

Cumulative radionuclide deposition (Bq m-2) per 1000 mm rainfall

Radionuclide deposition at the control sites, normalized using estimated rainfalls

TABLE 6

I,,J h.J

220

E J c . CURTIS ET A L

models for worldwide fallout inputs. The mean value derived from Table 6 is about 43%. The 137Cs figure, in the region of 3500-3600 Bam-'- per 1000 mm of rainfall, is close to the figure of 3200 Bq m -2 per lCO0mm rainfall reported by Cambray et al. [6]. The isotopic composition of the plutonium in the various soil samples gives some evidence of its origins. Plutonium taken from the control sites is indicated as being largely from fallout from atmospheric nuclear weapons explosions and, for 23Spu, accidental injection into the atmosphere from the burn-up in 1964 of a satellite, SNAP-9A. The ratios of 238pu/(239pu + 24°pu) by alpha-activity at the control sites (Table 7) approximate to the fallout ratio of 0.035 for the latitudes 40-60°N [7], and the norrnalised magnitude (Table 6) of the deposits approximate to Bennett's [4] 239pu + 24°pu fallout value for New York. The 23Spu/(239pu + 24°pu) ratios at the Sellafield zone also correspond to the nuclear weapons test fallout figure, but the quantities of radionuclides in the deposits are much larger than the nuclear test fallout values, indicating an aditional source of plutonium. Evidence that some of this plutonium originated from releases from Sellafield Works into the atmosphere has been provided by mass spectrometric measurements on environmental samples [8] and on human tissues taken at autopsy [9]. Plutonium for the Ravenglass zone has a 23Spu/(239pu + 24°pu) ratio markedly different from the plutonium ratios at the Sellafield zone and the control sites. Plutonium from the Ravenglass estuary is largely seaborne and is deposited according to tidal circumstances. Site 7 is frequently inundated by tides, Site 5 less so and Site 6 never. At Site 6 the absolute quantity of plutonium is hardly different from the nuclear weapons fallout value. The effect of tidal inundation on the radionuclide content of soil is evident from the results shown in Table 8. Cores from along the banks of the River Esk showed that radionuclide deposition was greatest in the lower tidal reaches of the river, and closest to the river banks. The results of this part of the survey are quoted as becquerels per kilogram dry weight of material, rather than in becquerels per unit area quoted at the sites where there is a stable soil profile. Data for the shores of the Duddon estuary are shown in the lower part of Table 8. Table 9 shows data from sites which were progressively more remote from Sellafield Works. The specific activity of the samples decreased with increasing distance along the coast. However, a referee points out, the decrease in activity could be due to different soil types at the various sites having differing absorptive properties. It is probable that the Esk samples consisted of silt + sand, whereas the Duddon samples may have been nearer to a normal sand that had a lower adsorptive capacity for water-borne radionuclides. The 238pu/(239pu + 24°pu) ratios (not shown) were similar to the Ravenglass values, attesting to their marine origin. High values of the 24~Am content of these sediments relative to the Dlutonium content contrast

Eskdale Near Dean Silecroft Scarness SW of Ulverston

4± + ± +

0.01 0.01 0.02 0.01 0.01

+ ± ± +

0.01 0.01 0.005 0.02

0.04 ± 0.01

0.05 __ 0.01 0.05 ± 0.01 0.09 ± 0.02

0.17 4- 0.02 0.15 +_ 0.03 0.19 ± 0.02

0.06 0.05 0.025 0.07

July 19~0 _+ 0.02 + 0.01 i 0.010 +_ 0.02

0.08 + 0.03 0.05 ± 0.02

0.065 4. 0.03

0.14 + (I.04 0.16 + 0.03 0.20 4. 0.02

0.09 0.04 0.03 u07

Sept. 1981 + 0.01 ± 0.01 _+ 0.01 _+ 0.01

(I.065 0.0'15 0.055 0.05 0.05

± 4. + i ±

0.01 0.01 0.02 0.02 0.02

0.15 ± 0.02 0.09 + 0.02 0.14 4- 0.07

0.06 0.05 0.03 0.05

Aug. 1982

0.05 0.07 0.06 0.06 0.04

_+ 0.01 4. 0.02 ± 0.02 ± 0.02 ± 0.01

0.14 _+ 0.02 0.11 4- 0.03 0.21 4- 0 0 4

0.07 _+ 0.OI

0.08 + 0.01 0.04 + 0.01

Sept. 1983

0.06 ± 0.01

0.13 4- 0.03 0.21 + 0.04

0.07 _+ 0.01

0.07 + 0.02 0.05 -I- 0.01

Sept. 1984

0.03 _ 0.01

0.15 + 0.03 0.2 4. 0.1

0.04 + 0.01

0.05 ± 0.01 0.03 ± 0.01

Sept. 1985

+ + ± ±

0.015 0.009 0.004 0.013

0.05 0.06 0.065 0.06 0.045

+ 0.01 __ 0.02 ± 0.02 ± 0.02 _+ 0.005

0.15 ± 0.0,'2 0.13 + 0.03 0.19 ± 0.02

0.065 0.041 0.030 0.060

Mean

"The error quoted for an individual value is twice the standard deviation of the propogated counting uncertainties, the uncertainty quoted for the mean value is the standard deviation of the mean on an n - ! basis.

8, 9, 10. II. 12,

0.045 0.035 0.055 0.04 0.045

0.17 +_ 0.02 0.12 4. 0.02 0.19 4. 0.03

5 6 7

4

__ 0.01 + 0.01 + 0.01 +_ 0.02

0.05 0.03 0.03 0.05

July-Aug. 1979

I 2 3

Site

:'tSPR/(239pu + 24°pu) by activity in mat plus soil"'

TABLE 7

I,d

222

E.J.O CURTIS E l AL.

TABLE 8 Radionuclides in soil cores (Bq kg-' dry weight) Esk and Duddon estuaries Site River Esk (1984) 13 ~ 14 15

:~'~P u + .~4,P u

..4, A m

:~7 Cs

9340 985 335

12100 1040 440

9750 1220 668

16 17 18

332 386 8.0

348 380 19

2640 696 35

19 20 21

651 334 200

825 413 214

1050 740 460

22

3.4

3. I

39

23

!.2

0.7

52

Duddon estuary

1984

1985

1984

1985

1984

1985

741 910

1380 660

710 !160

1600 870

1520 1470

3140 1800

26 27

793 2120

830 1490

980 2640

900 1700

1570 6160

1560 3610

28 29

1500 353

!i00 520

1800 395

1700 610

3540 1160

2250 !140

30 31

291 312

32 33 34 35 36

301 407

24 h 25

37 38

290 370 390 272 455 261 230 1570

330 478

1500 900 440 290 540 260 410 2400

1400 !100

890 650 1030 500 1050 3620

~'The data are arranged in groups so that progressing down the groups corresponds to sites progressively further upstream. Thus Sites 13-15 are nearest the mouth of the estuary and Site 23 is farthest. Within a particular group the lowest numbered site is nearest the river, and the highest numbered site is farthest from the river. Thus, in its group. Site 13 is closest to the river and Site 15 is farthest. , The numbering system follows, in general, the system for the Esk estuary. Sites 24 and 25 are near Millom and Sites 30 and 31 are near the head of the estuary. Sites 32-36 are in a clusler on the east bank of thc estuary. Exceptionally, Sites 37 and 38 are on the shores of Walney Isle.

RADIOACTIVITYIN ENVIRONMENTALSAMPLES

223

TABLE 9

Radionuclides in soil cores (Bq kg-~ dry weight). Leven and Kent estuaries, 1985

Site

-"~Pu + '4°pu

.'41 Am

~37Cs

Leven estuary 39 ~ 40

127 177

174 221

1130 900

230 215

270 280

1580 1560

64 47

75 66

640 700

4:: 40

125 250

180 200

1040 1890

47 48

67 !13

81 132

630 1020

49 50

75 170

71 290

710 890

41 42

Kent estuary 43 h 4,~

"One pair of sites on each shore of the estuary. 39 and east shore. In each pair. the lower numbered is closer "Sites 43 and 44 are on the west shore and 45 and 46 and 490 and 50 are between the Kent estuary mouth Morecambe.

40 on the west shore. 41 and 42 on the to the water. are on the east shore: Sites 47 and 48, and a point a few kilometers north of

with the nuclear weapons fallout values shown in Table 6. Enhanced radioactivity levels were readily measurable even at the sampling point most remote from Sellafield Works. Thus the plutonium concentrations in soils from the control sites were about 1-2 Bq kg-~ dry weight, and the ~.~TCsconcentrations were about 35 Bq kg -~ , whereas the lowest values for shoreline samples of soil from Morecambe Bay were several tens of becquerels per kilogram of plutonium and several hundreds of becquerels per kilogram of ~37Cs (Table 9). The ~.~7Cs activity of the various samples was measured by gamma-spectrometry. Other radionuclides besides ~37Cs were seen in many samples, particularly core samples from the estuarine regions. Usually, ~a7Cswas by far the predominant activity, with "'~'Ru/IIl~'Rh being generally < 20% of the ~7 Cs value. For example, sample 38 (Table 8), having 3620 Bq kg -~ ~37Cs, had additionally 36.4 Bq k g ~ ~4Cs, 350Bq kg ~ "'"Ru, and lesser amounts of 9~Zr/'~5Nb, 6°Co and 154Eu. Occasionally, ~0~,Ru/~,,~,Rh was present in substantial amounts, up to 93% of the ~;Cs level in sample 24 (Table 8) taken from near the water's edge in the Duddon estuary in 1984. Caesium-137 and

224

E.J.C. CURTIS ET AL.

106RU/I06 Rh were the only radionuclides to be found in activities greater than the natural potassium in the samples. The Ministry's annual Aquatic Environment Monitoring Reports [10] have routinely reported analyses of surface intertidal sediments for a number of the coastal areas sampled in the present report. Insofar as these data are comparable they are consistent with the present findings.

Sheep samples To relate the above measurements to food-chain radiation dose to man, a series of analyses was carried out on sheep that had been reared on the salt marshes in the vicinities of the estuaries of the Esk, Duddon and Leven, that is, the sites from which soil cores had been taken. The animals were usually 5to 7-year-old ewes that had failed to conceive, and had been selected and their histories verified by Field Officers from the MAFF Agricultural Development and Advisory Service. Animals of this age can be expected to have higher radionuclide contents than the younger animalsthat routinely enter the food chain. Samples were received initially as dressed carcasses as supplied to butchers, direct from the slaughterhouse. Occasionally, fairly large differences were noted between some specific activities of different sheep from the same flock, for example for the actinides of animals 3 and 4 from the west shore of the Duddon estuary, as shown in Table :i>. In order to show that this was a valid observation and not due merely to analytical error, all of the meat from the right-hand side of each carcass was homogenised and aliquots taken for analysis. In a similar fashion, aliquots were prepared from meat from the left-hand side of each carcass and analysed, Generally, there was good ageement between the analyses from the different sides of an animal, suggesting strongly that variations between different animals from the same flock were valid observations. The specific activities of the tissues are recorded in Table 10. Acknowledging that the mean value for the Esk estuary region (Table 10) relies on just two sheep of somewhat different levels of activity, there is a diminution of the specific activity of the sheep tissues with increasing distance betwen Sellafield Works and the grazing area of the flocks, reflecting the levels of activity deposited on the salt marshes (Tables 8 and 9). Actinide concentrations in liver and rib, in particular for the estuarine and coastal sheep, are markedly higher than the values for the control sheep. Table 10 shows also that the t37Cs levels of the November 1986, post-Chernobyl accident control animals are slightly higher than those of the control sheep, taken in January 1985, before the Chernobyl accident. It is possible that some of the radioactivity in the sheep sampled after May 1986 originated from the Chernobyl accident, though the range of

1985 1985 1986 1986 1986 1986

Jan. I { 85 Nov. ! a86 Nov. I o86

Control I 2

I 2 I

I 2 3 4 5 6

I 2 3 4 5 6

I 2

Animal number Rib

Long bone

0.00035 < 0.001 0.0008 (0.000~)

0.0030 0.0023 0.0013 0.0023

0.0090 00054 0.01 0.0049 0.0047 0.0043 0.0052

0.0054 0.001~ 0.0137 0.0041 0.0026 0.0059 00047

0,005 0.0092 0.007

0.008 0,004 0.009 0.008

0.14 0.72 0.24 0.24

2.5 0.52 0.97 1.2 0.92 0.93 0.95

1.3 0.75 1.5 2.9 0.39 0.79 1.05

1.3 2.9 (2. I )

0.0621 0.0017

0,025 0.022

0.052 0.019

0.013 0.018

0.032 0.03.;

0.017 0.43

0.0009 0,0019 0.0006

0.15 0.14

0.36 0.18 0.34 0.13 0.17 0.14

0.34 0.15 0.58 0.20 0.17 0.18

0.094 0.63

< 0,002 < 0.002

0.046 0.088 0.065

0.22 0,080

0.089 0.021

0.21 0.097

0.033 0.24

0.0005 0.0006 0.003 0.0005

0.0055 0.0041 0,012 0.0055

0.0185 0.0054 0.024 0.012 0.017 0,013 0.015

0.0075 0.0065 0.027 0.01 0.006 0.83 0.0087

0.006 0.030

Meat

Lung

Meat

Liver

241Am

239pu + 24°pu

0,003 0,002 0,002 0,002

0.10 0.59 0.79 0.59

0.75

1.7 0.52 0.74 0.75 0.66

0.98

1.9 0.86 1.3 1.8 0.31

1.0 1.9 (1.45)

Liver

0.002 0.003

0.038

0.12 0.019

0.40

0.1)89 0,062

0.039 0.34

Lung

11.003 0.002

0.30 ¢.26

0.57 0.18 0.52 0.17 0.39

0.76 0.30 1.3 0.30 0.42

0.21 0.97

Rib

0.002

0.49 0.08

0.47 0.19

0.070 0.86

Long bone

< 0.2 2.8 2. I

2.2 0.7 12

0,8 1.5 13 23 28 12

16 0.8 4.0 12 25 5.0 8.5

49 23

Meat

137Cs

0.2 1.2 2.6

0,5 0,4 4.5

0.3 0.8 7.6 41 21 9.7

4.1 4.6 8.5 18 4. I

3.1

8 8

Liver

aThe propagate~ "ounting uncertainties depended on the size of the sample and the quantity of radionuclide in the sample. The uncertainties in the actinides analyses of the liver were usually better than 5% (2~); the uncertainties in the meat values were usually better than 10% and the bone better than 5%. Uncertainties in the control actinide values were almost equal to the magnitude of the results. Caesium-137 uncertainties were usually better than 10%, but up to 100% for the January 1985 control,

Median

Oct. 1985 Oct. 1985 Jan. 10'~7 Media ~

Median

Jan. Jan. Oct. Oct. Oct. Oct.

Levens estuary

E. shore, Duddon estuary

1985 1985 1985 1985 1986 1987

Median

Jan. Jan. Oct. Oct. Oct. Jan.

Mean

Dec. 1983 Dec. 1983

Esk estuary

W. shore, Duddon estuary

Date

Sample region

Radionuclides in sheep tissues (Bq kg-i fresh weight) ~

TABLE l0

I,O bo

226

E.J.C. CURTIS ET AL.

specific activities seen in the various animals other than the controls would make it unlikely that an effect could be detected. For some of the carcasses, aliquots from all the various disected homogenised tissues were analysed, with the objective of measuring the whole body distribution of the actinides. The plutonium results are shown in Table 11. The proportion of the plutonium activity that was present in a particular tissue of the carcass varied from animal to animal, though the figure for the meat was fairly constant, averaging 4.5%. Clearly the liver is richest in plutonium, with significant amounts in the bone. The plutonium ratio in the liver/liver + bone varied from 39 to 71% and depended on the size of the animal and in particular the size of the liver. The assessment of the internal radiation dose delivered ~o a consumer of mutton and liver is dependent on the consumption rates. For lamb and mutton the critical group consumption rate is taken to be 30kgyear -~ by NRPB [11]. Currently, M A F F prefers to use a total of 125kgyear -I for its assessments of meats other than poultry, venison and game [12]. The reason for doing this rather than using figures for individual meats, as NRPB does, is that M A F F regard carcass meats to be to a large extent interchangeable in the diet. The larger data set which is then available means that M A F F figures should be that much more robust. Using their current figure, NRPB calculates a generalised derived limit ( G D L ) v f 40 Bq kg -t for mutton and lamb for each of "-',~:~isotopes 238pu, 2agpu, 24°pu, and 241 ~m. The total of the median concentrations of these isotopes in the Duddr a estuary sheep meat was about 0.016 Bq kg -~ , which is 0.04% of the GDL. For liver the NRPB G D L for each of the plutonium and americium isotopes being considered is 50 Bq kg -~ , and the sum of the median concentrations of the plutonium and americium isotopes in the Duddon estuary sheep was about 2.25 Bq kg -~ , which is about 4.5% of the GDL.

Bee/'analyses Beef is produced under farming conditions that are somewhat difli~rent from the conditions under which sheep from the estuarine area are reared. The beef cattle taken for analysis were about 2 years old at slaughter and had been raised on farms some way inland and remote from the influence of seaborne nuclear waste. Some previously reported results [13] on the radionuclide content of cattle were from dairy cows that had been chosen because it was thought that they would have the greatest likelihood of radionuclide uptake because of their age and grazing locations. In contrast, the current cattle samples were more related to tte beef supply likely to be found at the retailer. The analytical results from the beef cattle (Table 12) contrast markedly with the results from the sheep. The results on the west Cumbrian beef

0.070 0.13 0.050 0.07 0.05 0.02

W. Duddon, No. 5 W. Duddon, No. 6 E. Duddon, No. 4 E. Duddon, No. 5 E. Duddon, No. 6 Levens

0.46 0.64 !.0 0.86 0.72 0. ! 7

Liver

a Dates of sampling are shown ;n Table 10.

Meat

Animal

1.48 i .93 1.48 1.56 !.41 0.46

0.22 0.22

0.19 0.33 0.09 0.17 0.13 0.05

0.31 0.41 0.19 0.18 0.23 0.10

0.22 0.19 0.13 0.16 0.14 0.065

0.008 0.010 0.015 0.12

0.12 0.05

Dressed carcass total Remainder

Long bones, pelvic girdle

Vertebrae

Clavicles, scapulae, ribs

Lungs

Whole dressed sheep carcass distribution of z39Pu + 24°pu (Bq per carcass)'

TABLE i I

t'..~ t,.,) ...j

Near head of Kent estuary N. of Cockermouth Northallerton

Origin of the animal