Beresford, Nicholas A.

Carr, James

Killey, R.W. Doug

King-Sharp, K.

Robertson, Erin

Wood, Michael D.

Yankovich, Tamara L.

NERC Open Research Archive

This version available at http://nora.nerc.ac.uk/508526    NERC has developed NORA to enable users to access research outputs wholly or partially funded by NERC. Copyright and other rights for material on this site are retained by the rights owners. Users should read the terms and conditions of use of this material at http://nora.nerc.ac.uk/policies.html#access           Conference or Workshop Item    Yankovich, Tamara L.; Carr, James; Robertson, Erin; King-Sharp, K.; Killey, R.W. Doug; Beresford, Nicholas A.; Wood, Michael D. 2014. Spatial distribution and dynamics of carbon-14 in a wetland ecosystem. [Poster] In: 3rd International Conference on Radioecology and Environmental Radioactivity, Barcelona, 7-12 Sept 2014.                         Contact CEH NORA team at  noraceh@ceh.ac.uk  The NERC and CEH trademarks and logos (‘the Trademarks’) are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. Spatial Distribution and Dynamics of Carbon-14 in a Wetland EcosystemTamara L. Yankovich1, James Carr2, Erin Robertson3, K. King-Sharp2, R.W. Doug Killey2, Nicholas A. Beresford4,5, Michael D. Wood51International Atomic Energy Agency, P.O. Box 100, 1400 Vienna, Austria; 2Atomic Energy of Canada Limited, Chalk River Laboratories, Chalk River, Ontario, K0J 1J0, Canada; 3201 21st Street East, Saskatoon, SK S7K 0B8, Canada; 4,5NERC Centre for Ecology & Hydrology, Lancaster Environment Center, Bailrigg, Lancaster, LA14AP, UK;  5School of Environment & Life Sciences, University of Salford, Manchester, M44WT, UKINTRODUCTIONThere is significant interest in assessing the potential impact of 14C releases from nuclear facilities, radioactive waste management areas, and geologic disposal facilities.  As a result, there is a general need to gain understanding of 14C dynamics, including in complex interface ecosystems, such as wetlands (Stark et al., 2014; Yankovich et al., 2013, 2014).  Due to physical transport processes (e.g., via groundwater), radionuclides, such as 14C, can show localized spatial distributions in natural systems, such as wetlands. As a result, a key question from the perspective of environmental impact assessment (EIA) and monitoring is:  how do localized distributions of radionuclides in the environment influence the radiological doses to organisms?  To address this question, studies have been undertaken in Duke Swamp, a 0.1 km2 wetland, consisting of marsh, fen and swamp habitats, on the Atomic Energy of Canada Limited (AECL)’s Chalk River Laboratories (CRL) Site.  The swamp receives radionuclides, including 14C, from an up-gradient waste management area (WMA) (Killey et al., 1998), and 14C modelling results suggest that it represents >90% of total dose to resident animals (Zach et al., 1998).  An initial study was conducted involving an extensive field sampling campaign to measure 14C specific activity in surface vegetation across the swamp to evaluate the spatial distribution of 14C (Yankovich et al., 2014).  Representative receptor plants and animals, and corresponding environmental media (including air, soil, and plant) samples were subsequently collected at a subset of six locations with 14C specific activities that spanned the range present in Duke Swamp and which represented the different wetland habitats occurring there (Yankovich et al., 2013).  The objective of this paper is to predict doses to resident biota from 14C based on measurements of wildlife collected in Duke Swamp.  MATERIALS AND METHODSA detailed field campaign was carried out in summer 2001 to characterize the spatial distribution and areal coverage of 14C in Duke Swamp  (Killey et al., 1998).  Surface vegetation (predominantly Sphagnum moss) was sampled in the summer of 2001 at 69 locations on a 50 m x 50 m grid, with complementary sampling in 2002 of air, soil, fungi, aerial insects, ground-dwelling insects, amphibians, snakes and mammals at a subset of six locations with varying 14C concentrations (Yankovich et al., 2013, 2014).  Samples were analyzed to characterize 14C specific activities (Table 1).  Dose rates to resident biota from 14C were then estimated based on measured data using the ERICA (Environmental Risk from Ionising Contaminants: Assessment and Management) software tool (http://www.erica-tool.com/).  Tier 2 of the tool was used since site-specific 14C measurements were available for Duke Swamp environmental media and wildlife species.  ERICA default parameters were used for the screening level (10 μGy/h) and radiation weighting factors.  RESULTS AND CONCLUSIONSThe highest specific activities in surface vegetation were in a highly localized area of Duke Swamp (Site 35 in Table 1) where groundwater contaminated by the up-gradient WMA reaches the surface. This area of localised  high specific activities has been estimated to be about 150 m2 only (Yankovich et al., 2014).  In general, it was found that specific activities of 14C in biota tissues reflected those measured in air and surface vegetation collected from the same sampling location (Yankovich et al., 2013). There was a tendency for the specific activities in amphibians and reptiles to be higher than those in mammals and insects. This may be due to the increased exposure of reptiles and amphibians to groundwater. Additionally the specific activity in the muscle of white-tailed collected from the site road immediately adjacent to Duke Swamp was determined to be 199 14C Bq kg-1 C.For the purposes of this assessment, predictions of radiological dose rates to relevant reference organisms, including Lichens and Bryophytes (to represent Sphagnum moss in the swamp), Flying insects (to represent aerial insects), Detritivorous invertebrates (to represent ground beetles), Amphibians (to represent resident frog species), Reptiles (to represent garter snakes), Mammal (Rat) (to represent small mammals), and Mammal (Deer) (to represent white-tailed deer), were conducted. The assessment was conducted using the maximum measure specific activity for each organism group. Carbon-14 specific activities (in Bq/kg C) were converted to activity concentrations (in Bq/kg fresh mass) assuming: (i) 95%, 50 %, 18% and 33 %  carbon for moss, vertebrates, aerial insects and ground beetles on a dry mass basis, respectively; and (ii) 85%, 80%, 70% and 60% water contents for moss, vertebrates, aerial insects and ground beetles, respectively. These conversion data were based upon measurements made in Duke Swamp.The estimated activity concentrations in the organisms were then input into the ERICA tool to estimate dose rates. Based on this assessment, it was determined that predicted total dose rates for Duke Swamp biota fell below the screening dose rate of 10 µGy/hour, with risk quotients ranging from 5.9 x 10-5 for white-tailed deer to 0.019 for Sphagnum moss (Table 2). The external dose rate for all species was estimated to be 0 µGy/hour. Dose rates were similar to those reported by Stark et al. (2014), which presented results generated by different international dose models, as part of the International Atomic Energy Agency (IAEA)’s Environmental Modelling for Radiation Safety (EMRAS) II program (http://www-ns.iaea.org/projects/emras/emras2/default.asp?s=8&l=63).Table 1:  Summary results of 14C analyses of environmental media and resident animals collected in Duke Swamp in 2001-2002.  Year ofa Mean 14C Specific Activity (Bq/kg C dry mass) ± Standard Error [n](Minimum – Maximum)Sample Type Collection Site 9 Site 24 Site 27 Site 29 Site 35 Site 56Soil 2001 n.a. n.a. 38,247 [1] 1,546 [1] n.a. n.a.2002 714 [1] 560 [1] 22,145 [1] 2,363 [1] 84,900 (estimated using moss-to-soil relationship)7,279 [1]Sphagnum moss 2001 1,607 [1] n.d. 17,337 [1] 3,465 [1] 46,684 [1] 2,809 [1]2002 n.a. n.a. n.a. n.a. 48,152 ± 4.927 [5](30,371 - 56,811)n.a.Aerial insects 2002 679 [n = 1 composite]n.a. n.a. n.a. n.a. n.a.Ground beetles 2002 n.a. n.a. n.a. n.a. n.a. 1,201 (n = 1 composite)Amphibians (adult) 2001 n.a. n.a. n.a. n.a. b 49,681 [1] n.a.2002 2,406 ± 561 [6](731 – 3,869)453 ± 25.5 [4](385 – 503)38,854 [1] 5,193 ± 32.0 [2](5,161 – 5,225)106,515 [1] 6,750 ± 1,562 [3](4,455 – 9,734)Small mammals (carcass)2001 n.a. n.a. n.a. n.a. 5,713 ± 1,696 [6](1,649 – 11,620)n.a.Small mammals (carcass)2002 n.a. n.a. 3,694 ± 1,012 [3](2,446 – 5,698)2,015 ± 119 [2](1,896 – 2,133)16,554 [1] n.a.Snakes (carcass) 2002 1,798 [1] n.a. n.a. n.a. 39,863 ± 488 [2](38,969 – 40,538)n.a.a n.a. – data are not available; n.d. – not detectable ; n – number of samples analyzed for 14C; n.a. – not available; b Leopard frog captured between Site 27 and Site 35.Table 2:  Predicted dose rates for Duke Swamp wildlife species based upon maximum measured activity concentrations in biota.Reference Organism Species Total Dose Rate (µGy/hour)Lichen and Bryophyte Sphagnum spp. 0.19Flying insects Aerial insects 0.0011Detritivorous insects Ground beetle 0.0041Amphibian Rana pipiens, Rana catesbeiana 0.14Reptile Thamnophis sirtalis 0.12Mammal (Rat) Blarina brevicauda, Peromyscus leucopus, Microtus pennsylvanicus0.034Mammal (Deer) Odocoileus virginianus 0.00059ACKNOWLEDGEMENTThe authors would like to acknowledge Atomic Energy of Canada Limited (AECL) for their support of this work.REFERENCESArmstrong, W.E. and E.L. Young.  2000.  White-tailed deer management in Texas Hill Country.  Texas Parks and Wildlife.  http://www.tpwd.state.tx.us/publications/pwdpubs/media/pwd_rp_w7000_0828.pdf. Kilpatrick, H.J., S.M. Spohr, and K.K. Lima.  2001.  Effects of population reduction on home ranges of female white-tailed deer at high densities.  Canadian Journal Zoology, 79(6): 949-954.Killey, R.W.D., R.R. Rao and S. Eyvindson.  1998.  Radiocarbon speciation and distribution in an aquifer plume and groundwater discharge area, Chalk River, Ontario.  Applied Geochemistry, 13: 3-16.Stark, K., P. Andersson, N.A. Beresford, T.L. Yankovich, M.D. Wood, M.P. Johansen, J. Vives i Batlle, J. Twining, D-K. Keum, A. Bollhöfer, C. Doering, B. Ryan, M. Grzechnik, and H. Vandenhove.  2014.  Predicting exposure of wildlife in radionuclide contaminated wetland ecosystems:  An international biota dose model inter-comparison.  Submitted to Environmental Pollution.Yankovich, T.L., K.J. King-Sharp, M.L. Benz, J. Carr, R.W.D. Killey, N.A. Beresford and M.D. Wood.  2013.  Do site–specific radiocarbon measurements reflect localized distributions of 14C in biota inhabiting a wetland with point contamination sources.  Journal of Environmental Radioactivity, 126: 352-366.Yankovich, T.L., K.J. King-Sharp, J. Carr, E. Robertson, R.W.D. Killey, N.A. Beresford and M.D. Wood.  2014.  Spatial analysis of Carbon-14 dynamics in a wetland ecosystem (Duke Swamp, Chalk River Laboratories, Canada).  Journal of Environmental Radioactivity, In press.Zach, R., J.H. Rowat, G.M. Dolinar, S.C. Sheppard and R.W.D. Killey.  1998.  Ecological risk assessment for the proposed IRUS low level waste disposal facility at AECL’s Chalk River Laboratories.  Atomic Energy of Canada Limited Technical Record, AECL-TR-791.  

Spatial distribution and dynamics of carbon-14 in a wetland ecosystem

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Spatial distribution and dynamics of carbon-14 in a wetland ecosystem

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