A dynamic model for assessing radiological consequences of routine releases in the Loire river: parameterisation and uncertainty/sensitivity analysis

A dynamic model for assessing the transfer of several radionuclides ((58)Co, (60)Co, (110 m)Ag, (134)Cs, (137)Cs, (54)Mn and (131)I) in a food-chain was applied on the Loire river, where 14 nuclear power plants situated on five different sites operate. The model considers the following potential exposure pathways: (i) transfer of radionuclides through the aquatic food chain and the subsequent internal exposure of humans due to ingestion of contaminated water and/or fish; (ii) use of river water for agricultural purposes (irrigation), transfer of radionuclides through the terrestrial food chain and the subsequent internal exposure of humans due to ingestion of contaminated foodstuffs; (iii) internal exposure due to inhalation of dust originating from resuspension of contaminated soil particles; (iv) external exposure from radionuclides present in the river or deposited on the river sediments or the soil. For each of the parameters introduced in this model, a probability density function, allowing further uncertainty and sensitivity analysis, was proposed. Uncertainty/sensitivity analysis were performed to: (i) compare calculations to empirical data; (ii) determine a confidence interval for the mean annual dose to critical groups; and (iii) identify the parameters responsible for the uncertainty and subsequent research priorities.     

Comparison and analysis of different approaches for estimating the human exposure to phthalate esters

The human exposure estimates for dibutyl (DBP) and bis(2-ethylhexyl) phthalate (DEHP) made by two models EUSES and ACC-Human, and by an estimation approach which utilized measured concentrations in exposure media, were compared. The approach which utilized the latest monitoring data for important exposure media, yielded median daily intakes for adult humans for DBP and DEHP of 2.7 and 5.6 microg/kg body weight per day, respectively, which were in the same range as previous estimates based on back-calculation from urinary metabolites. EUSES estimated average daily intakes of DBP and DEHP for humans that were between 8 and 13 times lower. ACC-Human does not estimate average daily intakes, but ACC-Human-estimated human milk concentrations/fugacities were more than a thousand times lower than measured concentrations/fugacities in human milk. It was concluded that the two models underestimate human exposure to phthalate esters because they consider only a few key pathways that are known to be important for other, more persistent, hydrophobic organic compounds. Further, it was shown that there are differences between the two models on the methodology for estimating concentrations in exposure media such as vegetation, milk, beef and fish. ACC-Human uses a mechanistic approach for estimating transfer through aquatic and terrestrial food chains that are known to be important for human exposure to persistent, hydrophobic organics and can, unlike EUSES, account for food chain metabolism. It proved difficult, however, to obtain organism metabolism rates needed as model inputs to ACC-Human. If exposure estimates of phthalate esters are needed, it is recommended to use an estimation approach based on high quality monitoring data as presented here and/or back-calculate daily intake from concentrations of metabolites in human urine samples from the general population.     

Cobalt and secondary poisoning in the terrestrial food chain: data review and research gaps to support risk assessment

Cobalt is a naturally occurring element found in rocks, soil, water, plants, and animals and has diverse industrial importance. It is cycled in surface environments through many natural processes (e.g. volcanic eruptions, weathering) and can be introduced through numerous anthropogenic activities (e.g. burning of coal or oil, or the production of cobalt alloys). The environmental behaviour of cobalt in terrestrial environment is relatively poorly studied and in particular where Co is used in industrial processes, the baseline information to support wider and long-term environmental impacts is widely dispersed. To support the adoption of new EU regulations on the risk assessment of chemicals, we review here the various aspects of the environmental chemistry, fate and transport of Co across environmental interfaces and discuss the toxicology and potential for bio magnification and food chain accumulation. The soil-to-plant transfer of Co appears to be viable route to expose lower trophic levels to biologically significant concentrations and Co is potentially accumulated in biomass and top soil. Evidence for further accumulation through soil-invertebrate transfer and to higher trophic levels is suggested by some studies but this is obscured by the relatively high variability of published transfer data. This variation is not due to one particular aspect of the transfer of Co in terrestrial environments. Influences are from the variability of geological sources within soil systems; the sensitivity of Co mobility to environmental factors (e.g. pH) and the variety of life strategies for metal elimination/use within biological species. Toxic effects of Co have been suggested for some soil-plant animal studies however, uncertainty in the extrapolation from laboratory to field is a major limitation.     

A probabilistic approach to obtaining limiting estimates of radionuclide concentration in biota

The US Department of Energy has developed a graded approach for evaluating radiation doses to biota. Limiting concentrations of radionuclides in water, soil, and sediment were derived for twenty-three radionuclides. Four organism types (aquatic animals, riparian animals, terrestrial animals, and terrestrial plants) were selected as the basis for method development. While environmental transfer data needed for deriving biota tissue concentrations are available for aquatic animals and terrestrial plants, less information is available for terrestrial and riparian organisms. Two methods were applied and examined for their ability to provide estimates of organism:soil or organism:water concentration factors in lieu of measured data. The kinetic/allometric approach combined with a parameter uncertainty analysis provides a needed method to estimate concentration factors across multiple species with limited input data.     

The distribution of tritium in the terrestrial and aquatic environments of the Creys-Malville nuclear power plant (2002-2005)

The Creys-Malville nuclear plant, located on the left bank of the Rh?ne, was shut down in 1998. The facilities are currently in their initial stage of dismantling. In order to establish a baseline for tritium in the vicinity of the site prior to the main dismantling phase, we carried out a monitoring program between 2002 and 2005 in the main terrestrial and aquatic compartments of the local environment. Tritium levels in the groundwaters and in the Rh?ne waters correspond to the regional tritium concentration in precipitation. The data obtained for the terrestrial environment are also in good agreement with the regional background and do not show any specific signature linked to the nuclear plant. The various aquatic compartments of the Rh?ne (fish, plant, sediment) are significantly enriched in tritium both upstream and downstream of the power plant: although Tissue-Free Water Tritium concentrations are in equilibrium with the river water, the non-exchangeable fraction of organic bound tritium in plants and fishes shows values which outpace the river water background by one to two orders of magnitude, and up to four to five orders of magnitude in the sediments. This tritium anomaly is not related to the nuclear plant, as it is already present at the Swiss border 100km upstream of the site. Although fine particles of tritiated polystyrene entering the composition of the luminous paints used by the clock industry have been suspected on several occasions, the exact nature and the origin of this tritium source remain unknown and require further investigations.     

Modelling of long-term behaviour of caesium and strontium radionuclides in the Arctic environment and human exposure

In this paper a compartment model of the highly vulnerable Arctic terrestrial food chain "lichen-reindeer-man" is outlined. Based upon an analysis of measured (137)Cs and (90)Sr contents in lichen and reindeer meat from 1961 up to 2001, site specific model parameters for two regions in north-western Arctic Russia and for Kautokeino municipality in Arctic Norway have been determined. The dynamics of radionuclide activity concentrations in the "lichen-reindeer-man" food chain for all areas was satisfactorily described by a double exponential function with short-term and long-term effective ecological half-lives between 1-2 and 10-12 years, respectively, for both (137)Cs and (90)Sr. Using parameter values derived from the model, life-time internal effective doses due to consumption of reindeer meat by reindeer-breeders after an assumed single pulse deposit of 1 kBq m(-2) of (137)Cs were estimated to be 11.4 mSv (Kola Peninsula), 5 mSv (Nenets Autonomous Area), and 2 mSv (Kautokeino, Norway). Differences in vulnerability to radiocaesium deposition were due to differences in transfer between lichen and reindeer and in diet between the three regions.     

The ecological effects of trichloroacetic acid in the environment

Trichloroacetic acid (TCAA) is a member of the family of compounds known as chloroacetic acids, which includes mono-, di- and trichloroacetic acid. The significant property these compounds share is that they are all phytotoxic. TCAA once was widely used as a potent herbicide. However, long after TCAA's use as a herbicide was discontinued, its presence is still detected in the environment in various compartments. Methods for quantifying TCAA in aqueous and solid samples are summarized. Concentrations in various environmental compartments are presented, with a discussion of the possible formation of TCAA through natural processes. Concentrations of TCAA found to be toxic to aquatic and terrestrial organisms in laboratory and field studies were compiled and used to estimate risk quotients for soil and surface waters. TCAA levels in most water bodies not directly affected by point sources appear to be well below toxicity levels for the most sensitive aquatic organisms. Given the phytotoxicity of TCAA, aquatic plants and phytoplankton would be the aquatic species to monitor for potential effects. Given the concentrations of TCAA measured in various soils, there appears to be a risk to terrestrial organisms. Soil uptake of TCAA by plants has been shown to be rapid. Also, combined uptake of TCAA from soil and directly from the atmosphere has been shown. Therefore, risk quotients derived from soil exposure may underestimate the risk TCAA poses to plants. Moreover, TCE and TCA have been shown to be taken up by plants and converted to TCAA, thus leading to an additional exposure route. Mono- and di-chloroacetic acids can co-occur with TCAA in the atmosphere and soil and are more phytotoxic than TCAA. The cumulative effects of TCAA and compounds with similar toxic effects found in air and soil must be considered in subsequent terrestrial ecosystem risk assessments.     

Transport and fate of radionuclides in aquatic environments--the use of ecosystem modelling for exposure assessments of nuclear facilities

In safety assessments of nuclear facilities, a wide range of radioactive isotopes and their potential hazard to a large assortment of organisms and ecosystem types over long time scales need to be considered. Models used for these purposes have typically employed approaches based on generic reference organisms, stylised environments and transfer functions for biological uptake exclusively based on bioconcentration factors (BCFs). These models are of non-mechanistic nature and involve no understanding of uptake and transport processes in the environment, which is a severe limitation when assessing real ecosystems. In this paper, ecosystem models are suggested as a method to include site-specific data and to facilitate the modelling of dynamic systems. An aquatic ecosystem model for the environmental transport of radionuclides is presented and discussed. With this model, driven and constrained by site-specific carbon dynamics and three radionuclide specific mechanisms: (i) radionuclide uptake by plants, (ii) excretion by animals, and (iii) adsorption to organic surfaces, it was possible to estimate the radionuclide concentrations in all components of the modelled ecosystem with only two radionuclide specific input parameters (BCF for plants and Kd). The importance of radionuclide specific mechanisms for the exposure to organisms was examined, and probabilistic and sensitivity analyses to assess the uncertainties related to ecosystem input parameters were performed. Verification of the model suggests that this model produces analogous results to empirically derived data for more than 20 different radionuclides.     

Effect of user interpretation on uncertainty estimates: examples from the air-to-milk transfer of radiocesium

An important source of uncertainty in predictions of numerical simulation codes of environmental transport processes arises from the assumptions made by the user when interpreting the model and the scenario to be assessed. This type of uncertainty was examined systematically in this study and was compared with uncertainty due to varying parameter values in a code. Three terrestrial food chain codes that are driven by deposition of radionuclides from the atmosphere were used by up to ten participants to predict total deposition of ¹³⁷Cs and concentrations on pasture and in milk for two release scenarios. Collective uncertainty among the predictions of the ten users for concentrations in milk calculated for one scenario by one code was a factor of 2000, while the largest individual uncertainty was 20 times lower. Choice of parameter values contributed most to user-induced uncertainty, followed by scenario interpretation. Due to the significant disparity in predictions, it is recommended that assessments should not be carried out alone by a single code user.     

Rain scavenging of tritiated water vapour: a numerical Eulerian stationary model

The tradition in tritium washout modeling is to unite the washout model with a Gaussian plume model describing dispersion of tritium vapour in the atmosphere. In the present study, an alternative approach is proposed. A numerical Eulerian model that describes washout independently of dispersion is developed.The sensitivity analysis to model parameters has shown that the washout process is influenced most significantly by rainfall parameters and air temperature: different raindrop size distributions cause differences of up to about 70% in the washout outputs; a change of 15 °C in the air temperature causes an effect of about 50%.Results are presented showing calculated values of washout outputs (tritium concentration in rain, tritium downward flux, washout coefficient) for different tritium vapour profiles, rainfall rates and air temperatures. The general conclusion is that the washout process is too complex to be described comprehensively by the simple washout coefficient concept. We suggest the approach proposed here for directly calculating the tritium downward flux and concentration in the rainwater is preferable.     

Proposal for new best estimates of the soil-to-plant transfer factor of U,Th, Ra,Pb and Po

There is increasing interest in radiological assessment of discharges of naturally occurring radionuclides into the terrestrial environment. Such assessments require parameter values for the pathways considered in predictive models. An important pathway for human exposure is via ingestion of food crops and animal products. One of the key parameters in environmental assessment is therefore the soil-to-plant transfer factor to food and fodder crops. The objective of this study was to compile data, based on an extensive literature survey, concerning soil-to-plant transfer factors for uranium, thorium, radium, lead, and polonium. Transfer factor estimates were presented for major crop groups (Cereals, Leafy vegetables, Non-leafy vegetables, Root crops, Tubers, Fruits, Herbs, Pastures/grasses, Fodder), and also for some compartments within crop groups. Transfer factors were also calculated per soil group, as defined by their texture and organic matter content (Sand, Loam, Clay and Organic), and evaluation of transfer factors' dependency on specific soil characteristics was performed following regression analysis. The derived estimates were compared with estimates currently in use.     

Derivation of a screening methodology for evaluating radiation dose to aquatic and terrestrial biota

The United States Department of Energy (DOE) currently has in place a radiation dose standard for the protection of aquatic animals, and is considering additional dose standards for terrestrial biota. These standards are: 10 mGy/d for aquatic animals, 10 mGy/d for terrestrial plants, and, 1 mGy/d for terrestrial animals. Guidance on suitable approaches to the implementation of these standards is needed. A screening methodology, developed through DOE's Biota Dose Assessment Committee (BDAC), serves as the principal element of DOE's graded approach for evaluating radiation doses to aquatic and terrestrial biota. Limiting concentrations of radionuclides in water, soil, and sediment were derived for 23 radionuclides. Four organism types (aquatic animals; riparian animals; terrestrial animals; and terrestrial plants) were selected as the basis for development of the screening method. Internal doses for each organism type were calculated as the product of contaminant concentration, bioaccumulation factor(s) and dose conversion factors. External doses were calculated based on the assumption of immersion of the organism in soil, sediment, or water. The assumptions and default parameters used provide for conservative screening values. The screening methodology within DOE's graded approach should prove useful in demonstrating compliance with biota dose limits and for conducting screening assessments of radioecological impact. It provides a needed evaluation tool that can be employed within a framework for protection of the environment.     

Perfluoroalkyl carboxylates and sulfonates and precursors in relation to dietary source tracers in the eggs of four species of gulls (Larids) from breeding sites spanning Atlantic to Pacific Canada

In the present study, we identified and examined the spatial trends, sources and dietary relationships of bioaccumulative perfluorinated sulfonate (PFSA; C(6), C(8), and C(10) chain lengths) and carboxylate (PFCA; C(6) to C(15) chain lengths) contaminants, as well as precursor compounds including several perfluorinated sulfonamides, and fluorotelomer acids and alcohols, in individual eggs (collected in 2008) from four gull species [glaucous-winged (Larus glaucescens), California (Larus californicus), ring-billed (Larus delawarensis) and herring (Larus argentatus) gulls] from 15 marine and freshwater colony sites in provinces across Canada. The pattern of PFSAs was dominated by perfluorooctane sulfonate (PFOS; >89% of ΣPFSA concentration) regardless of egg collection location. The highest ΣPFSA concentrations were found in the eggs collected in the urbanized areas in the Great Lakes and the St. Lawrence River area [Big Chicken Island 308 ng/g ww, Toronto Harbour 486 ng/g ww, and Ile Deslauriers (HG) 299 ng/g ww]. Also, eggs from all freshwater colony sites had higher ΣPFSA concentrations, which were significant (p<0.05) in many cases, compared to the marine sites with the exception of the Sable Island colony in Atlantic Canada off the coast of Nova Scotia. C(6) to C(15) chain length PFCAs were detected in the eggs, although the pattern was variable among the 15 sites, where PFUnA and PFTrA dominated the pattern for most colonies. Like the ΣPFSA, the highest concentrations of ΣPFCA were found in the eggs from Big Chicken Island, Toronto Harbour, Ile Deslauriers (HG), and Sable Island, although not all freshwater sites had higher concentrations compared to marine sites. Dietary tracers [δ(15)N and δ(13)C stable isotopes (SIs)] revealed that PFSA and PFCA exposure is colony dependent. SI signatures suggested that gulls from most marine colony sites were exposed to PFCs via marine prey. The exception was the Mandarte Island colony in Pacific British Columbia, where PFSA and PFCA exposure appeared to be via terrestrial and/or freshwater prey consumption. The same was true for the freshwater sites where egg SIs suggested both aquatic and terrestrial prey consumption as the source for PFC exposure depending on the colony. Both aquatic (marine and freshwater) and terrestrial prey are likely sources of PFC exposure to gulls but exposure scenarios are colony-specific.     

Comparative accumulation of (109)Cd and (75)Se from water and food by an estuarine fish (Tetractenos glaber)

Few data are available on the comparative accumulation of metal(loid)s from water and food in estuarine/marine fish. Smooth toadfish (Tetractenos glaber), commonly found in estuaries in south-eastern Australia, were separately exposed to radio-labelled seawater (14kBqL(-1) of (109)Cd and 24kBqL(-1) of (75)Se) and food (ghost shrimps; Trypaea australiensis: 875Bqg(-1)(109)Cd and 1130Bqg(-1)(75)Se) for 25 days (uptake phase), followed by exposure to radionuclide-free water or food for 30 days (loss phase). Toadfish accumulated (109)Cd predominantly from water (85%) and (75)Se predominantly from food (62%), although the latter was lower than expected. For both the water and food exposures, (109)Cd was predominantly located in the gut lining (60-75%) at the end of the uptake phase, suggesting that the gut may be the primary pathway of (109)Cd uptake. This may be attributed to toadfish drinking large volumes of water to maintain osmoregulation. By the end of the loss phase, (109)Cd had predominantly shifted to the excretory organs - the liver (81%) in toadfish exposed to radio-labelled food, and in the liver, gills and kidney (82%) of toadfish exposed to radio-labelled water. In contrast, (75)Se was predominantly located in the excretory organs (gills, kidneys and liver; 66-76%) at the end of the uptake phase, irrespective of the exposure pathway, with minimal change in percentage distribution (76-83%) after the loss phase. This study emphasises the importance of differentiating accumulation pathways to better understand metal(loid) transfer dynamics and subsequent toxicity, in aquatic biota.     

Assessment of the consequences of the radioactive contamination of aquatic media and biota for the Chernobyl NPP cooling pond: model testing using Chernobyl data

The ‘Cooling Pond’ scenario was designed to test models for radioactive contamination of aquatic ecosystems, based on data from the Chernobyl Nuclear Power Plant cooling pond, which was heavily contaminated in 1986 as a result of the reactor accident. The calculation tasks include (a) reconstruction of the dynamics of radionuclide transfer and bioaccumulation in aquatic media and biota following the accident; (b) assessment of doses to aquatic biota; and (c) assessment of potential doses and radiation risks to humans from consumption of contaminated fish. Calculations for the Scenario were performed by 19 participants using 6 different models: LAKECO-B (Netherlands); LAKEPOND (Romania); POSOD (USA); WATER, GIDRO and ECOMOD-W (Russia). For all endpoints, model predictions were compared with the test data, which were derived from the results of direct measurements and independent dose estimates based on measurements. Most of the models gave satisfactory agreement for some portions of the test data, although very few participants obtained good agreement with all criteria for model testing. The greatest level of difficulty was with the prediction of non-equilibrium radioecological processes in the first year after the accident (1986). The calculations 5 for this scenario gave modellers a unique opportunity to test their models using an independent data base and to analyse the advantages and weaknesses of different model approaches. The use of post-Chernobyl data in such a scenario is also recommended for use in training students in the field of radioecology and environmental protection.     

Development and validation of a dynamical atmosphere-vegetation-soil HTO transport and OBT formation model

A numerical model simulating transport of tritiated water (HTO) in atmosphere-soil-vegetation system, and, accumulation of organically bound tritium (OBT) in vegetative leaves was developed. Characteristic of the model is, for calculating tritium transport, it incorporates a dynamical atmosphere-soil-vegetation model (SOLVEG-II) that calculates transport of heat and water, and, exchange of CO₂. The processes included for calculating tissue free water tritium (TFWT) in leaves are HTO exchange between canopy air and leaf cellular water, root uptake of aqueous HTO in soil, photosynthetic assimilation of TFWT into OBT, and, TFWT formation from OBT through respiration. Tritium fluxes at the last two processes are input to a carbohydrate compartment model in leaves that calculates OBT translocation from leaves and allocation in them, by using photosynthesis and respiration rate in leaves. The developed model was then validated through a simulation of an existing experiment of acute exposure of grape plants to atmospheric HTO. Calculated TFWT concentration in leaves increased soon after the start of HTO exposure, reaching to equilibrium with the atmospheric HTO within a few hours, and then rapidly decreased after the end of the exposure. Calculated non-exchangeable OBT amount in leaves linearly increased during the exposure, and after the exposure, rapidly decreased in daytime, and, moderately nighttime. These variations in the calculated TFWT concentrations and OBT amounts, each mainly controlled by HTO exchange between canopy air and leaf cellular water and by carbohydrates translocation from leaves, fairly agreed with the observations within average errors of a factor of two.     

Rodents as receptor species at a tritium disposal site

New methods are being employed on the Department of Energy's Savannah River Site to deal with the disposal of tritium, including the irrigation of a hardwood/pine forest with tritiated water from an intercepted contaminant plume to reduce concentrations of tritium outcropping into Fourmile Branch, a tributary of the Savannah River. The use of this system has proven to be an effective means of tritium disposal. To evaluate the impact of this activity on terrestrial biota, rodent species were captured on the tritium disposal site and a control site during two trapping seasons in order to assess tritium exposure resulting from the forest irrigation. Control site mice had background levels of tritium, 0.02 Bq/mL, with disposal site mice having significantly higher tritium concentrations, mean=34.86 Bq/mL. Whole body tritium concentrations of the mice captured at the disposal site were positively correlated with tritium application and negatively correlated with precipitation at the site.     

Inorganic arsenic in Chinese food and its cancer risk

Even moderate arsenic exposure may lead to health problems, and thus quantifying inorganic arsenic (iAs) exposure from food for different population groups in China is essential. By analyzing the data from the China National Nutrition and Health Survey (CNNHS) and collecting reported values of iAs in major food groups, we developed a framework of calculating average iAs daily intake for different regions of China. Based on this framework, cancer risks from iAs in food was deterministically and probabilistically quantified. The article presents estimates for health risk due to the ingestion of food products contaminated with arsenic. Both per individual and for total population estimates were obtained. For the total population, daily iAs intake is around 42 μg day(-1), and rice is the largest contributor of total iAs intake accounting for about 60%. Incremental lifetime cancer risk from food iAs intake is 106 per 100,000 for adult individuals and the median population cancer risk is 177 per 100,000 varying between regions. Population in the Southern region has a higher cancer risk than that in the Northern region and the total population. Sensitive analysis indicated that cancer slope factor, ingestion rates of rice, aquatic products and iAs concentration in rice were the most relevant variables in the model, as indicated by their higher contribution to variance of the incremental lifetime cancer risk. We conclude that rice may be the largest contributor of iAs through food route for the Chinese people. The population from the South has greater cancer risk than that from the North and the whole population.     

Cs-137 in Arctic foxes (Alopex lagopus) on Svalbard

This study presents 137Cs muscle activity concentrations in Arctic foxes (Alopex lagopus) from Svalbard over a period of several years and discusses the transfer of 137Cs to Arctic foxes through likely predator--prey relationships. Mean 137Cs activity concentrations and 137Cs Tag values (per trapping season) ranged from 0.51+/-2.76 to 1.32+/-2.89 Bq/kg (w.w.) and 5.1 x 10(-4) to 1.3 x 10(-3)m(2)/kg, respectively. Mean concentration ratios of 137Cs in Arctic foxes compared to probable prey ranged from 1.0 to 7.9. On Svalbard, transfer of 137Cs to Arctic foxes is likely to occur via both marine and terrestrial food chains. The relative contribution of marine and terrestrial food sources to the diet of Arctic foxes may vary by location and by season and may lead to either an increase or decrease in the trophic transfer of 137Cs to Arctic foxes compared to transfer resulting from terrestrial only diets.     

Role of allochthonous carbon in the energy of terrestrial invertebrate communities at different distances from the Black Sea and a freshwater lake (Isotopic Evidence)

Isotopic analysis has become an important tool in the study of lateral links between ecosystems. The isotopic composition of carbon in terrestrial and aquatic primary producers can differ significantly, which provides an opportunity to identify the “marine” or “freshwater” carbon in the tissues of terrestrial animals. We measured the isotopic composition of C and N in tissues of soil invertebrates and estimated the proportion of “aquatic” carbon in the energy budget of terrestrial food webs at different distances from the Black Sea and a freshwater lake. Terrestrial predators are actively subsidized with carbon from the Black Sea to distance of up to about 50 m. The carbon subsidy from the freshwater lake is significant in the zone extending no farther than the forest border (ca. 15 m). Thus, the effect of allochthonous organic matter on terrestrial communities in both cases manifests itself only in a relatively narrow coastal strip.