The Sellafield nuclear fuel reprocessing plant on the northwest coast of England is the largest source of anthropogenic radiocarbon to the UK coastal environment. In a mid-1990s study of C-14 distribution around the UK coast, the pattern of dilution with increasing distance from Sellafield appeared to be perturbed by anomalously high C-14 activities in marine biota in the coastal environment of northeast England. This present study was undertaken during 1998 and 1999 to determine whether this C-14 enhancement was due to Sellafield or the nuclear power plants on the east coast. Seawater, seaweed (Fucus sp.), and mussel (Mytilus edulis) samples that were collected from the vicinity of the Torness and Hartlepool advanced gas-cooled reactor (AGR) nuclear power stations were all enhanced above the contemporary regional background activity derived from natural production and atmospheric nuclear weapons testing. We used previously published dilution factors and transfer times for Tc-99 between Sellafield and various points on the UK coast to determine likely Sellafield- derived C-14 contributions to the activities at the nuclear power plant sites. The results suggest that the activities observed at Torness, which are only marginally enhanced above the natural background activity, are possibly due to discharges from Sellafield; however, the significant C-14 enhancements at Hartlepool are not Sellafield-derived. Furthermore, since both reactors have the same fundamental design, the low activities at the Torness AGR imply that the activities at Hartlepool are not from the AGR, suggesting that there is an input of C-14 to the marine environment in the vicinity of Hartlepool which is probably non-nuclear-power related. However, there is no other authorized site in the area that could account for the observed C-14 enrichments; therefore, further research is required to ascertain the source of this C-14

Anderson, R.

Cook, G.T.

Gulliver, P.

MacKenzie, A.B.

Naysmith, P.

Radiocarbon

English

From the 18th International Radiocarbon Conference held in Wellington, New Zealand, September 1-5, 2003.The Sellafield nuclear fuel reprocessing plant on the northwest coast of England is the largest source of anthropogenic radiocarbon to the UK coastal environment. In a mid-1990s study of 14C distribution around the UK coast, the pattern of dilution with increasing distance from Sellafield appeared to be perturbed by anomalously high 14C activities in marine biota in the coastal environment of northeast England. This present study was undertaken during 1998 and 1999 to determine whether this 14C enhancement was due to Sellafield or the nuclear power plants on the east coast. Seawater, seaweed (Fucus sp.), and mussel (Mytilus edulis) samples that were collected from the vicinity of the Torness and Hartlepool advanced gas-cooled reactor (AGR) nuclear power stations were all enhanced above the contemporary regional background activity derived from natural production and atmospheric nuclear weapons testing. We used previously published dilution factors and transfer times for 99Tc between Sellafield and various points on the UK coast to determine likely Sellafield-derived 14C contributions to the activities at the nuclear power plant sites. The results suggest that the activities observed at Torness, which are only marginally enhanced above the natural background activity, are possibly due to discharges from Sellafield; however, the significant 14C enhancements at Hartlepool are not Sellafield-derived. Furthermore, since both reactors have the same fundamental design, the low activities at the Torness AGR imply that the activities at Hartlepool are not from the AGR, suggesting that there is an input of 14C to the marine environment in the vicinity of Hartlepool which is probably non-nuclear-power related. However, there is no other authorized site in the area that could account for the observed 14C enrichments; therefore, further research is required to ascertain the source of this 14C.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information.Migrated from OJS platform February 202

Cook, G. T.

MacKenzie, A. B.

The University of Arizona

Sources of Anthropogenic 14C to the North Sea

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Sources of anthropogenic C-14 to the North Sea

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RADIOCARBON, Vol 46, Nr 2, 2004, p 869–875  © 2004 by the Arizona Board of Regents on behalf of the University of Arizona© 2004 by the Arizona Board of Regents on behalf of the University of ArizonaProceedings of the 18th International Radiocarbon Conference, edited by N Beavan Athfield and R J SparksRADIOCARBON, Vol 46, Nr 2, 2004, p 869–875869SOURCES OF ANTHROPOGENIC 14C TO THE NORTH SEAP Gulliver1,2 • G T Cook1 • A B MacKenzie1 • P Naysmith1 • R Anderson1ABSTRACT. The Sellafield nuclear fuel reprocessing plant on the northwest coast of England is the largest source of anthro-pogenic radiocarbon to the UK coastal environment. In a mid-1990s study of 14C distribution around the UK coast, the patternof dilution with increasing distance from Sellafield appeared to be perturbed by anomalously high 14C activities in marinebiota in the coastal environment of northeast England. This present study was undertaken during 1998 and 1999 to determinewhether this 14C enhancement was due to Sellafield or the nuclear power plants on the east coast. Seawater, seaweed (Fucussp.), and mussel (Mytilus edulis) samples that were collected from the vicinity of the Torness and Hartlepool advanced gas-cooled reactor (AGR) nuclear power stations were all enhanced above the contemporary regional background activity derivedfrom natural production and atmospheric nuclear weapons testing. We used previously published dilution factors and transfertimes for 99Tc between Sellafield and various points on the UK coast to determine likely Sellafield-derived 14C contributionsto the activities at the nuclear power plant sites. The results suggest that the activities observed at Torness, which are only mar-ginally enhanced above the natural background activity, are possibly due to discharges from Sellafield; however, the signifi-cant 14C enhancements at Hartlepool are not Sellafield-derived. Furthermore, since both reactors have the same fundamentaldesign, the low activities at the Torness AGR imply that the activities at Hartlepool are not from the AGR, suggesting thatthere is an input of 14C to the marine environment in the vicinity of Hartlepool which is probably non-nuclear-power related.However, there is no other authorized site in the area that could account for the observed 14C enrichments; therefore, furtherresearch is required to ascertain the source of this 14C.INTRODUCTIONA 1995 investigation of 14C activities in the UK coastal marine environment (Cook et al. 1998) ana-lyzed the dissolved inorganic carbon (DIC) component of seawater, seaweed (Fucus species), andflesh from mussels (Mytilus edulis), crab (Cancer pagurus), flatfish (plaice), and roundfish (cod).The study revealed a pattern of dilution of 14C activity in the DIC with increasing distance from Sell-afield (the largest source of anthropogenic 14C to the coastal waters of the British Isles) in a clock-wise manner around the British Isles, i.e., in the direction of the prevailing currents. The trend wasperturbed by anomalously high 14C activities at Whitby, located on the east coast of the British Isles(Figure 1). As the 14C activities in the north of Scotland were significantly lower than those foundat Whitby, Cook et al. (1998) concluded that the net activities found at Whitby were possibly due toreleases from the nearby nuclear power producing facility at Hartlepool (Figure 1), which was oneof the first advanced gas-cooled reactors (AGR) commissioned in the British Isles.The use of Sellafield-derived radionuclides as a tracer for water movement is well established, andthese studies have shown that the Sellafield discharges are carried north from the Irish Sea, throughthe North Channel (Figure 1), along the west coast of Scotland, around the north coast of Scotland,and subsequently south along the east coast of the UK (Jefferies et al. 1973, 1982; Prandle 1984;Dahlgaard 1995; Nines 1990; Kershaw and Baxter 1995). Recent studies using Sellafield-derived99Tc indicate transport times of approximately 9 and 24 months to Pentland Firth and Lowestoft(270 km south of Whitby), respectively (Leonard et al. 1997; McCubbin et al. 2002) (Figure 1). Inorder to investigate whether or not the activities above ambient background at Whitby were ananomaly or were a common feature close to AGR facilities, this study was carried out to investigate14C activities in the vicinity of Hartlepool and another AGR facility at Torness (Figure 1) in south-1Scottish Universities Environmental Research Centre, Scottish Enterprise Technology Park, East Kilbride G75 0QF,Scotland.2NERC Radiocarbon Laboratory, Scottish Enterprise Technology Park, East Kilbride G75 0QF, Scotland.Corresponding author. Email: P.Gulliver@nercrcl.gla.ac.uk.870 P Gulliver et al.east Scotland. Samples were obtained from the immediate vicinity of the Hartlepool AGR in 1998and 1999, and from the vicinity of the Torness AGR in 1999. METHODS AND MATERIALSThe following suite of samples was collected from the vicinity of both the Hartlepool and Tornessnuclear power plants: DIC extracted from 100 L of water, seaweed (Fucus sp.), and mussels (Myti-lus edulis).The water samples were acidified, purged with nitrogen, and the CO2 collected and converted tobenzene for radiometric analysis, as described in Gulliver et al. (2001). The seaweed samples werewashed thoroughly and then dried. The mussels were boiled briefly to aid removal of the flesh andthen freeze-dried. These samples were then combusted and the CO2 converted to benzene (Gulliveret al. 2001).  Figure 1 Map of the United Kingdom indicating sampling and other sites referenced in the textSources of Anthropogenic 14C to the North Sea 871At Torness, the samples were collected close to the coolant water outflow pipeline. At Hartlepool,the samples were collected from Parton Rocks, approximately 3 miles from the nuclear plant. RESULTS AND DISCUSSION 14C activities (Bq kg–1 C) for the DIC and biota samples are presented in Table 1 as net activitiesabove the relevant ambient background, which depends on the year of collection and species. Thebackground activities were derived from Burtonport (Figure 1), a site on the west coast of Irelandwhich is not significantly influenced by discharges from the Sellafield plant (Cook et al. 1998;Gulliver et al. 2001). Also included for reference are net 14C activities (Bq kg–1 C) for the samplescollected in 1995 from Whitby on the NE coast of England (Cook et al. 1998). The 14C activities of all samples are enhanced above ambient background, while the Hartlepoolsamples are all more highly enriched than those from either Torness or Whitby. The questions raisedby these results are the following: • What is the source of the enhancements above ambient background at both Torness and Hartle-pool? • Why is there such a difference between the 2 sites?Based on low 14C activities of samples from northern Scotland, Cook et al. (1998) discounted theinfluence of Sellafield-derived 14C discharges on the activities found at Whitby in NE England.However, it can be observed from Figure 2 that there was a large increase in 14C discharges fromSellafield in 1994/95, around the time of their study. Sellafield-derived 99Tc has much in commonwith Sellafield-derived 14C. Both have been discharged since 1952; they have similar, recent dis-charge histories (Figure 2), including a peak in discharges during 1994/95; they have long half-lives(99Tc has a half-life of 2.3 × 105 yr); and they behave in a conservative manner in the marine envi-ronment. In particular, 99Tc has a low Kd in sediments that are low in organic matter, such as thoseof the Irish Sea. Recent studies using Sellafield-derived 99Tc as a tracer of water movement givetransit times of 15–18 months from Sellafield to the east coast of the UK (Leonard et al. 1997;McCubbin et al. 2002). The 1994/95 peak in 99Tc discharge activities and the propagation of thispeak through UK coastal waters was studied in detail, with results indicating that the leading edgeof the peak had traveled around the north coast of Scotland and as far south as latitude 52° northwithin 9 months (McCubbin et al. 2002). A further study has shown that the leading edge reachedArctic waters between 1998 and 1999 (Kershaw et al. 2004). If we use transport of Sellafield-derived 99Tc as a proxy for Sellafield-derived 14C transport in UK coastal waters, this implies thatthe activities found at Torness and Hartlepool in 1998 and 1999 could not be due to the peak in 14Cdischarges from Sellafield in 1994/1995. In addition, if there was any contribution of 14C to theactivities found at Hartlepool or Torness, then it would be from discharges from Sellafield madeapproximately 15–18 months prior to the collection of samples for this study.Table 1 Net 14C activities (Bq kg–1 C ± 1 σ) in DIC, seaweed, and mussels collected fromthe vicinity of the Hartlepool and Torness AGRs (1998 and 1999) and from Whitby (1995).Location Sampling date DIC Mussels SeaweedWhitbyaaFrom Cook et al. (1998).1995 23 ± 5 11 ± 3 23 ± 3Hartlepool 1998 104 ± 4 561 ± 4 55 ± 3Hartlepool 1999 94 ± 5 913 ± 4 50 ± 4Torness 1999 16 ± 4 38 ± 3 27 ± 2872 P Gulliver et al.From Tables 1 and 3, it can be observed that 14C activities in the vicinity of Hartlepool fall withinthe range measured at the North Channel. While it is unlikely that transport of 14C in the DIC wouldnot result in dilution, it is hard to be definitive about this without data from an additional site situatedbetween Sellafield and the NE coast of England. Unfortunately, this study did not investigate 14Cactivities in the marine environment from northern Scotland, unlike the study of Cook et al. (1998).However, estimates of DIC 14C activity at Cape Wrath (Figure 1) can be made using (i) dilution fac-tors between the North Channel and Cape Wrath calculated by McCubbin et al. (2002) for 1993 to1996 using 99Tc (see Table 2), and (ii) DIC 14C activities from the North Channel collected betweenAugust 1997 and July 1999 (Table 3). The North Channel DIC 14C activities reflect discharges fromSellafield made 3–6 months prior to the collection date, and so are representative of Sellafield dis-charges that would reach Torness and Hartlepool 15–18 months after the date of discharge. Due tovariations in current flux and 14C discharge from Sellafield, there are obvious assumptions in usingdilution factors for 1993 to 1996 and 14C data for 1997 to 1999; however, neither the dilution factors(4.7 to 12.2) nor the DIC 14C activities at the North Channel (101–271 Bq kg–1) vary greatly overthis period. Therefore, the estimates (8.2 to 57.7 Bq kg–1 C) (Table 2) based on these data are usefulin providing the only probable range of DIC 14C activities for Cape Wrath during this time. The net14C activity for the DIC at Torness falls within this range, suggesting that at least part of theenhancement above ambient background may be Sellafield-derived. In contrast, the net activities inthe DIC at the Hartlepool site are greater than this range. In view of the dilution that 14C undergoesduring transport and the fact that Torness is significantly closer to Sellafield than Hartlepool, itwould seem unlikely that the enhancements above ambient background at Hartlepool are Sellafield-derived, although some contribution from Sellafield cannot be ruled out. As both the Hartlepool andTorness nuclear plants have the same fundamental design, the low activities at the Torness AGRFigure 2 14C and 99Tc discharges from the Sellafield nuclear fuel reprocessing plant (1952–2000)1950 1960 1970 1980 1990 2000Year05010015020099Tc discharges (TBq)048121614C discharge (TBq)14C99TcSources of Anthropogenic 14C to the North Sea 873imply that the significantly higher activities found at Hartlepool are not from the AGR, although onthe evidence available some contribution cannot be ruled out. Net activities in mussels from Hartlepool were 561 ± 4 Bq kg–1 C in 1998 and 913 ± 4 Bq kg–1 C in1999. These activities are significantly higher than those found at the North Channel; indeed, the netmussel activity in 1999 falls within the range of activities found at Nethertown (Table 3), close toSellafield (Figure 1). Comparison of the Hartlepool data and data from a site very close to Amer-sham International plc (Cook et al. 1998) indicates certain similarities. The Amersham data had anexcess 14C ratio of approximately 10:1 for mussels:seaweed, which was interpreted as indicating asignificant organic component in the discharges. The enhancements in mussels relative to seaweedat Hartlepool are 11:1 for 1998 and 18:1 for 1999. These ratios are greater than the Amersham ratio,implying that the discharges close to Hartlepool also have an organic component. The activities inmussels are similar in magnitude at the Amersham and Hartlepool sites, implying a similar sizeddischarge to Amersham (1–2 TBq during this period), close to the Hartlepool sampling site, orindeed, a greater sized discharge at distance. However, the only other authorized nuclear site in thearea was a small test reactor that ceased operations in 1996, and subsequent discharges are under theheading of beta/gamma and ranged from 9.69 × 10–8 to 9.79 × 10–7 TBq between 1996 and 1999(CEFAS 1997–2000). The magnitude of these discharges is much too small to account for theobserved enrichments at Hartlepool. We therefore have no obvious explanation for these anoma-lously high 14C activities.CONCLUSIONSThere are 14C enrichments in biota around the Hartlepool and Torness AGRs. Both have the samefundamental design, and so would be expected to have the same 14C formation and discharge path-ways; however, the activities around Hartlepool are significantly greater.Hartlepool is significantly further away from Sellafield than Torness, implying that the activities arenot Sellafield-derived.Using dilution factors for Sellafield-derived 99Tc between the North Channel and Cape Wrath and14C data from the North Channel, it was possible to calculate likely 14C activities at Cape Wrath.These data demonstrated that the 14C discharges from Sellafield could be a significant contributor tothe net DIC activities found in the vicinity of the Torness AGR but are not responsible for the netDIC activities found in the vicinity of the Hartlepool AGR.The activities in mussels were significantly greater than those in the DIC and seaweed, implying thepossibility of an organic 14C discharge in the vicinity of Hartlepool; however, the only other autho-rized discharge in the area appears too small to account for the activities.Table 2 99Tc dilution factors between the North Channel and Cape Wrath (from McCubbin etal. 2002) and estimated 14C activities in the DIC fraction of the water column at Cape Wrath.Survey date 99Tc dilution factor Estimated 14C activity (Bq kg–1 C)December 1993 12.2 5.5–22.2December 1994 8.0 8.4–22.9December 1995 9.1 7.4–29.8December 1996 4.7 14.3–57.7874 P Gulliver et al.It is also unlikely that the Hartlepool AGR is the source of organic 14C as there is no evidence of anorganic 14C discharge in the vicinity of Torness and there is no known pathway for a significant pro-duction/discharge of organic 14C from these reactors.A further and more extensive investigation into 14C distributions in the marine environment aroundHartlepool is required to determine the location, discharge activities, and impact of the anthropo-genic source of 14C in this area.ACKNOWLEDGEMENTSWe gratefully acknowledge Magnox Electric plc and the Industry Management Committee for theirfinancial support of this study under Contract BL/G/51919/E.REFERENCESTable 3 Net 14C activities (i.e. above ambient background) in mussels (Mytilus edulis) and theDIC fraction of the water column (Bq kg–1 C ± 1 σ) collected at Nethertown and the North Channel.Nethertown North ChannelCollection date Mussels DIC Mussels DICAug. 97 813 ± 4 440 ± 5 120 ± 4 120 ± 4Sept. 97 956 ± 7 1012 ± 7 116 ± 4 117 ± 4Oct. 97 1045 ± 4 2779 ± 9 111 ± 4 116 ± 4Nov. 97 1104 ± 4 1335 ± 7 118 ± 4 111 ± 4Dec. 97 1188 ± 5 3283 ± 9 111 ± 4 171 ± 4Jan. 98 1197 ± 6 2956 ± 10 101 ± 4 271 ± 5Feb. 98 1210 ± 6 3208 ± 15 117 ± 4 164 ± 4Mar. 98 1216 ± 5 8057 ± 25 110 ± 5 150 ± 4Apr. 98 1300 ± 5 2379 ± 9 116 ± 4 109 ± 4May 98 1983 ± 8 3212 ± 11 108 ± 3 123 ± 4June 98 1918 ± 8 5807 ± 27 115 ± 4 130 ± 6July 98 1827 ± 8 4656 ± 15 108 ± 4 136 ± 5Aug. 98 1812 ± 7 998 ± 5 106 ± 4 126 ± 4Sept. 98 1596 ± 6 598 ± 5 105 ± 4 122 ± 4Oct. 98 1569 ± 9 344 ± 4 109 ± 4 101 ± 6Nov. 98 1555 ± 7 1453 ± 7 102 ± 4 124 ± 4Dec. 98 1526 ± 10 520 ± 4 102 ± 4 136 ± 4Jan. 99 1444 ± 7 1400 ± 7 106 ± 4 115 ± 4Begg FH. 1992. Anthropogenic 14C in the natural aquaticenvironment [PhD dissertation]. Glasgow: Universityof Glasgow.Begg FH, Baxter MS, Cook GT, Scott EM, McCartneyM. 1991. Anthropogenic 14C as a tracer in westernU.K. coastal waters. In: Kershaw PJ, Woodhead DS,editors. Radionuclides in the Study of Marine Pro-cesses. New York: Elsevier Applied Science. p 52–60.Begg FH, Cook GT, Baxter MS, Scott EM, McCartneyM. 1992. Anthropogenic radiocarbon in the EasternIrish Sea and Scottish coastal waters. Radiocarbon34(3):707–16.CEFAS (Centre for Fisheries, and Aquaculture Science).1997–2000. Radioactivity in Food and the Environ-ment (RIFE). Report to the Food Standards Agencyand Scottish Environment Protection Agency.Cook GT, Mackenzie AB, Naysmith P, Anderson R.1998. Natural and anthropogenic 14C in the UKcoastal marine environment. Journal of Environmen-tal Radioactivity 40(1):89–111.Dahlgaard H. 1995. Transfer of European coastal pollu-tion to the Arctic: radioactive tracers. Marine Pollu-tion Bulletin 31:3–7.Gulliver P, Cook GT, Mackenzie AB, Naysmith P, Ander-son R. 2001. Transport of Sellafield-derived 14C fromthe Irish Sea through the North Channel. RadiocarbonSources of Anthropogenic 14C to the North Sea 87543(2B):869–77.Gulliver P. 2002. Geochemistry and budgetary consider-ations of 14C in the Irish Sea [PhD dissertation]. Glas-gow: University of Glasgow.Jefferies DF, Preston A, Steele AK. 1973. Distribution of137Cs in British coastal waters. Marine PollutionBulletin 4:118–22.Jefferies DF, Steele AK, Preston A. 1982. Further studieson the distribution of 137Cs in British coastal waters. 1.The Irish Sea. Deep-Sea Research 29:713–38.Kershaw PJ, Baxter A. 1995. The transfer of reprocess-ing waste from northwest Europe to the Arctic. Deep-Sea Research II 42:1413–48.Kershaw PJ, Heldal HE, Mork KA, Rudjord AL. 2004.Variability in the supply, distribution and transport ofthe transient tracer 99Tc in the NE Atlantic. Journal ofMarine Systems 44(1–2):55–81.Leonard KS, McCubbin D, Brown F, Bonfield R, BrooksT. 1997. Distribution of Technetium-99 in UK coastalwaters. Marine Pollution Bulletin 34(8):628–36.McCubbin D, Leonard KS, Brown J, Kershaw PJ,Bonfield RA, Peak T. 2002. Further studies of the dis-tribution of technetium-99 and caesium-137 in UKand European coastal waters. Continental Shelf Re-search 22:1417–45.Nies H. 1990. The contamination of the North Sea byartificial radionuclides during the year 1987. Journalof Environmental Radioactivity 11:55–70.Prandle D. 1984. A modelling study of the mixing of Csin the seas of the European continental shelf. Philo-sophical Transactions of the Royal Society London,Series A 310:407–36.

A modelling study of the mixing of Cs in the seas of the European continental shelf.

Anthropogenic 14C as a tracer in western U.K. coastal waters.

Channel Collection date Mussels DIC Mussels DIC

for Fisheries, and Aquaculture Science). 1997–2000. Radioactivity in Food and the Environment (RIFE). Report to the Food Standards Agency and Scottish Environment Protection Agency.

Further studies on the distribution of

Geochemistry and budgetary considerations of 14C in the Irish Sea [PhD dissertation].

Natural and anthropogenic 14C in the UK coastal marine environment.

The contamination of the North Sea by artificial radionuclides during the year

The transfer of reprocessing waste from northwest Europe to the Arctic. DeepSea Research II

Transfer of European coastal pollution to the Arctic: radioactive tracers.

Variability in the supply, distribution and transport of the transient tracer 99Tc in the NE Atlantic.

The Sellafield nuclear fuel reprocessing plant on the northwest coast of England is the largest source of anthropogenic radiocarbon to the UK coastal environment. In a mid-1990s study of 14C distribution around the UK coast, the pattern of dilution with increasing distance from Sellafield appeared to be perturbed by anomalously high 14C activities in marine biota in the coastal environment of northeast England. This present study was undertaken during 1998 and 1999 to determine whether this 14C enhancement was due to Sellafield or the nuclear power plants on the east coast. Seawater, seaweed (Fucus sp.), and mussel (Mytilus edulis) samples that were collected from the vicinity of the Torness and Hartlepool advanced gas-cooled reactor (AGR) nuclear power stations were all enhanced above the contemporary regional background activity derived from natural production and atmospheric nuclear weapons testing. We used previously published dilution factors and transfer times for 99Tc between Sellafield and various points on the UK coast to determine likely Sellafield-derived 14C contributions to the activities at the nuclear power plant sites. The results suggest that the activities observed at Torness, which are only marginally enhanced above the natural background activity, are possibly due to discharges from Sellafield; however, the significant 14C enhancements at Hartlepool are not Sellafield-derived. Furthermore, since both reactors have the same fundamental design, the low activities at the Torness AGR imply that the activities at Hartlepool are not from the AGR, suggesting that there is an input of 14C to the marine environment in the vicinity of Hartlepool which is probably non-nuclear-power related. However, there is no other authorized site in the area that could account for the observed 14C enrichments; therefore, further research is required to ascertain the source of this 14C.</jats:p

P Gulliver

G T Cook

A B MacKenzie

P Naysmith

R Anderson

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Sources of Anthropogenic <sup>14</sup>C to the North Sea

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Sources of anthropogenic C-14 to the North Sea

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