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Radionuclide sheet

Carbon-14 and the environment: appendices


 

Review of measurement methods

 

*The time shown is the "technical time" needed for analysis (processing of the dry sample and measurement). It does not integrate organisational constraints, such as the fact that heavy instrumentation (e.g. AMS) can generally only be used on a batch of samples, by campaign and on fixed dates.

 

 

Usual radioecological models (at equilibrium): terrestrial environment

 

The conventional evaluations of the radioecological impact of 14C in terrestrial ecosystems remain very empirical, implicitly or explicitly assuming a 14C/12C isotopic equilibrium in the soil-plant-atmosphere system. Recently, models related to biomass have been developed that take into consideration the dynamic nature of acute exposure (Tamponnet, 2005b, Galeriu et al., 2007).

 

Soil

 

Given that 14C is easily incorporated in food products and that humans mainly assimilate carbon by ingestion, the soil is not modelled as an exposure environment.

 

Models based on this assumption overlook the various soil compartments that may influence carbon isotope equilibrium. In addition, these models do not consider the physical/chemical form of the source term (whether the addition to the soil is liquid or solid), which will undergo a process of incorporation in the organic material cycle and/or be mineralised. A simplified model can be employed that uses default transfer factor values based on the assumption of 14C/12C isotopic equilibrium between organic matter in soil and in plant, but this substitute approach appears to be very conservative for evaluating plant transfer.

 

However, the importance of the soil is reflected in certain models, given that it is a potential source of contamination for plants, as indicated in the following section.

 

 

Plants

 

Carbon-14 transfer to plants is modelled with the assumption that the soil-atmosphere-plant equilibrium is perfectly reached. Most models only integrate atmospheric contamination subsequent to gaseous releases. During photosynthesis, CO2 is incorporated in organic matter, for which it contributes to the carbon skeleton. Equilibrium is then rapidly established between the specific activities of atmospheric CO2 and CO2 of organic plant material under construction.

 

The atmosphere -> plant transfer is modelled with the assumption that the specific activity (Bq of 14C per kg of 12C) of plant carbon is the same as the atmospheric specific activity. The underlying assumption is that the transfer of the trace radionuclide 14C is identical to 12C transfer and that the two compartments are at equilibrium. This results in the following equation (IAEA, 2010):

 

 

 

Proportion of stable carbon in terrestrial plants ( *1000, g C/kg wet)

 

 

The irrigation water -> plant transfer is modelled with the assumption that the 14C from irrigation is incorporated via photosynthesis, as a result of emanation of CO2 from the soil. The plant's activity concentration is evaluated by considering the 12C and 14C fluxes emanating from the soil, and the fraction of the carbon flux that comes from the soil and that participates in photosynthesis.

 

 

Transfer to plants from soil that is contaminated, in particular via liquids, is still poorly understood. The only recent work in this area was conducted as part of radioactive waste disposal studies (BIOPROTA, 2010).

 

 

Animals

 

Transfer to animal products is modelled based on the transfer pathway (atmospheric and/or liquid contamination pathway for plants included in the animals' food ration) according to the respective expressions:

 

* Factor  fcont is used to integrate the fact that animals can be fed with concentrates or from far-away sources that are not contaminated. The value of this factor should be based on local agricultural practices. If a site-specific value is not available, must be conservatively set to 1.

 

 

Proportion of stable carbon in animal products ( *1000, g C/kg wet)

 

 

 

Food processing

 

The effect of food processing is quantified by a transfer factor, also called a retention factor. This factor gives the fraction of radionuclide remaining in the product after processing.

 

Food processing transfer factor (Bq/kgwet of product processed by Bq/kgwet of unprocessed product)

(IAEA, 2010)

 

 

Usual radioecological models (at equilibrium): freshwater environments

Water and sediment

 

For drinking water, 14C concentration is assumed equal to the concentration in the original stream, river or well, with correction by a factor related to the treatment used, if necessary. The efficiency of drinking water treatment processes at removing 14C from supply water has not been studied.

 

Sediment is rarely taken into account in models for calculating doses resulting from exposure to 14C. The fraction of pollutant linked to the dissolved phase can, however, be calculated based on a Kd value of 2 x 103 m3/t dry weight.

 

 

Plants

 

The equation for phytoplankton and underwater plants is as follows:

 

 

 

Animals

 

For fish (or other animals), the released chemical forms, whether inorganic (proportion pm in liquid effluents) or organic (po = 1-pm), can be taken into account in the evaluation of transfers. Due to the slowness with which organic forms are transformed into inorganic forms, inorganic carbon-14 at equilibrium in the stream or river water comes only from liquid releases. Part of this carbon-14 has been used for photosynthesis; the inorganic forms available for animals are present at a proportion lower than pi, and the expression Cmin(water) = p1.Cwater can be considered conservative.

 

For organic forms, the balance at equilibrium is more complex, as a result of two competing effects. The first is that integration by the microbial loop of organic carbon-14 from the water in the stream or river tends to reduce the 14C proportion below po, and the second is that decay of contaminated preys and excrements of contaminated organisms tends to increase this proportion to above po. The following expression is only an approximation of organic carbon-14 activity in the stream or river water: . Given these assumptions, the following expression is used for initial approximation of the activity concentration of 14C in animals:

 

 

Proportion of stable carbon in aquatic plants and animals (kg of C/kg wet)

 

Primary producers

 

 

 

Fish

 

(Garnier-Laplace et al., 1998)

 

 

Radiotoxicological parameters

 

Dose conversion coefficients (DCCs), expressed in wet weight

 

Terrestrial environment

 

Freshwater

 

nd*: DCC not determined due to the distance or to the shield effect of sediment

 

 

Sea water

 

nd*: DCC cannot be determined because of distance


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14C environment sheet

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Contributors

Revision in 2010

  • Terrestrial ecosystem

Séverine Le Dizès-Maurel

  • Continental aquatic ecosystem

Frédéric Alonzo

  • Marine ecosystem

Bruno Fiévet

  • Metrology

Béatrice Boulet

Jeanne Loyen

Jean-Louis Picolo

  • Concentrations in the environment

Philippe Renaud

 

Verification

Dominique Boust

Karine Beaugelin-Seiller

Christian Tamponnet

Selected bibliography

  • AFNOR (2006). Mesure de la radioactivité dans l'environnement. - Partie 2 : mesurage de l'activité du carbone 14 par scintillation liquide dans les matrices carbonées de l'environnement (indice de classement : M60-812-2). Norme NF M60-812-2, 35 p.
  • Amoros C and Petts GE (1993). Hydrosystèmes fluviaux. Collection d’écologie, Masson, Paris.
  • Beaugelin-Seiller K, Jasserand F, Garnier-Laplace J, Gariel JC (2006). Modelling the radiological dose in non-human species: principles, computerization and application. Health Phys, 90 : 485-493.
  • BIOPROTA (2010). C-14 Long-Term Dose Assessment: Data Review, Scenario Development, and Model Comparison, WORKSHOP REPORT, L. Limer & M. Thorne (Eds), April 2010.
  • Calvin M and Benson AA (1948) .The Path of Carbon in Photosynthesis. Science 107: 476-480
  • Ciba-Geigy (1981). “Units of measurement, body fluids, composition of the body, nutrition”, Geigy Scientific Tables, Vol. 1, 8th edn, Ciba-Geigy Ltd., Basel (1981).
  • CE - Commission Européenne (2009). Nucleonica...web driven nuclear science. (page consulted 6 June 2011).
  • Douville E, Fiévet B, Germain P, Fournier M (2004). Radiocarbon behaviour in seawater and the brown algae Fucus serratus in the vicinity of the COGEMA La Hague spent fuel reprocessing plant (Goury) - France. J Environ Radioactiv 77: 335-368
  • Fiévet B, Voiseux C, Rozet M, Masson M, Bailly du Bois P (2006). Transfer of radiocarbon liquid releases from the AREVA La Hague spent fuel reprocessing plant in the English Channel. J Environ Radioactiv 90: 173-196
  • Fontugne M, Maro D, Baron Y, Hatté, Hébert D, Douville E (2004). 14C sources and distribution in the vicinity of La Hague nuclear reprocessing plant: Part 1. Terrestrial environment. Radiocarbon, 46 : 827-830.
  • Fournier M, Henry A, Loyen J (1999). Oxidiser et benzène : deux méthodes de mesurage du. 14C, Journées Techniques CETAMA « Mesures et analyses dans les matrices environnementales et biologiques ».
  • Galeriu D, Melintescu A, Beresford NA, Crout NMJ, Peterson R, Takeda H (2007) Modelling 3H and 14C transfer to farm animals and their products under steady state conditions. J Environ Radioactiv, 98:205-217
  • Garnier-Laplace J, Roussel-Debet S, Calmon P (1998). Modélisation des transferts du carbone 14, émis par les réacteurs à eau pressurisée en fonctionnement normal, dans l'environnement proche du site. Rapport IPSN/DPRE/SERE 98/007, IRSN, Cadarache.
  • IAEA (2010). Handbook of Parameter Values for the Prediction of Radionuclide Transfer in Terrestrial and Freshwater Environments, Technical Reports, Series No.472, IAEA, Vienna.
  • Khomyakova M, Bükmez Ö, Thomas LK, Erb TJ, Berg IA (2011) A Methylaspartate cycle in Haloarchaea. Science 331:334-337.
  • Le Dizès-Maurel S, Maro D, Lebaron-Jacobs L, Masson M (2009). « Carbone 14 », in Chapitre 31, Toxicologie nucléaire environnementale et humaine. Ménager M.T., Garnier-Laplace J., Goyffon M. (Coord). Editions Tex&Doc – Lavoisier., 603-618.
  • Maro D, Masson M, Fiévet B, Bailly du Bois P, Connan O, Boust D, Germain P (2008). Analyse critique des données disponibles de carbone 14 et de tritium dans le nord Cotentin et en Manche. IRSN, rapport DEI/SECRE 2008-006.
  • Ouyang Y and Boersma L (1992). Dynamic oxygen and carbon dioxide exchange between soil and atmosphere. Soil Science Soc Am J, 56: 1695-1710.
  • Roussel-Debet S (2007). Evaluation of 14C doses since the end of the 1950s in metropolitan France. Radioprotection, 42 (3): 297-313.
  • Roussel-Debet S. (2009). Bilan des mesures OPERA terrestre 2007-2008. IRSN, rapport DEI/SESURE 2009-19.
  • Roussel-Debet S, Gontier G, Siclet F, Fournier M (2006). Distribution of carbon 14 in the terrestrial environment close to French nuclear power plants. J Environ Radioact 87(3): 246-259
  • Roussel-Debet S, Claval D (2010). Constat radiologique régional -Étude prototype « Val de Loire ».IRSN, rapport DEI/SESURE 2010-22.
    Sellafield Ltd ( 2009). Monitoring our Environment. Discharges and Monitoring in the United Kingdom. Annual Report 2009. (Consulted 17 November 2010).
  • Scott EM, Baxter MS and McCartney M (1991). Considerations on the modelling of environmental radiocarbon. BIOMOVS. Symposium on the validity of environmental transfer models. Stockholm (Sweden). SSI. 498 Swedish Radiation Protection Institute, Stockholm (Sweden), pp. 107-123.
  • Sheppard S.C., Amiro B.D., Sheppard M.I., Stephenson M., Zach R., Bird G.A. (1994). Carbon-14 in the biosphere: Modeling and porting research for the Canadian Nuclear Fuel Waste Management program, Waste-Management, 14 (5) 445-456
  • Stumm W and Morgan JJ (1981). Aquatic Chemistry. John Wiley, New-York.
  • Tamponnet C (2005a) Dynamics of Carbon 14 in soils: A review, Radioprotection 40: 465-470.
  • Tamponnet C (2005b) Modelling Tritium and Carbon in the environment: A biomass-oriented approach, Radioprotection 40: 713-719.
  • United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) (1993). Report of the general assembly, with annexes. United Nations publications, New York.
  • United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) (2008). Sources and effects of ionizing radiation. Report Vol. I: sources. United Nations publications, New York.

Publications

Modelling transfers of carbon 14 emitted by pressurised water reactors under normal operating conditions, in continental ecosystems (05/06/2002)

S. Roussel-Debet, J. Garnier-Laplace, C. Mourlon and P. Calmon Actes du congrès ECORAD, 3-7 sept 2001, Aix en Provence, France Radioprotection - Colloques, volume 37, C1-141 / C1-146.


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