at SciVerse ScienceDirect

Journal of Environmental Radioactivity 108 (2012) 9e14

Contents lists available

Journal of Environmental Radioactivity

journal homepage: www.elsevier .com/locate/ jenvrad

Comparative analysis of doses to aquatic biota in water bodies impactedby radioactive contamination

A.I. Kryshev*, T.G. SazykinaState Institution Research and Production Association “Typhoon”, 4 Pobedy Str., Obninsk, Kaluga Region 249038, Russia

a r t i c l e i n f o

Article history:Received 30 December 2010Received in revised form4 April 2011Accepted 7 July 2011Available online 15 September 2011

Keywords:RadiationDoseEffectsAquaticBiotaFish

* Corresponding author. Tel.: þ7 48439 71769; fax:E-mail address: ecomod@obninsk.com (A.I. Kryshe

0265-931X/$ e see front matter � 2011 Elsevier Ltd.doi:10.1016/j.jenvrad.2011.07.013

a b s t r a c t

Comparative analysis of doses to the reference species of freshwater biota was performed for thefollowing water bodies in Russia or former USSR: Chernobyl NPPs cooling pond, Lakes Uruskul andBerdenish located in the Eastern Urals Radioactive Trace, Techa River, Yenisei River. It was concluded thatthe doses to biota were considerably different in the acute and chronic periods of radioactivecontamination. The most vulnerable part of all considered aquatic ecosystems was benthic trophic chain.A numerical scale on the “dose rate e effects” relationships for fish was formulated. Threshold dose ratesabove which radiation effects can be expected in fish were evaluated to be the following: 1 mGy d�1 forappearance of the first morbidity effects in fish; 5 mGy d�1 for the first negative effects on reproductionsystem; 10 mGy d�1 for the first effects on life shortening of fish. The results of dose assessment to biotawere compared with the scale “dose rate e effects” and the literature data on the radiobiological effectsobserved in the considered water bodies. It was shown that in the most contaminated water bodies thedose rates were high enough to cause the radiobiological effects in fish.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction

At present, development of the criteria which could ensure theradiation safety of non-human biota is an actual problem ofradioecology (ICRP, UNSCEAR, IAEA). Considerable internationalefforts are being directed during the recent years to the develop-ment of a system for radiological protection of the non-humanbiota in the natural environment. An important progress has beenachieved in creation of components for this system. Significantimprovements in methods for dose estimation in non-human biotawere achieved within the EPIC, FASSET, ERICA and PROTECT ECProjects (EPIC, 2003; Vives i Batlle et al., 2007; Ulanovsky and Pröhl,2008; Brown et al., 2008), also due to activity of the special workinggroups within the recent EMRAS and EMRAS II Programmes,organized by the International Atomic Energy Agency (http://www-ns.iaea.org/projects/emras/emras2). Some reference levelsof chronic exposures related to different types of effects in biotahave been suggested in the literature (UNSCEAR, 1996; DOE, 2002;Garnier-Laplace and Gilbin, 2006; Sazykina et al., 2009; ICRP, 2009).

It is important to evaluate a range of exposure levels which werereally observed in various radioecological situations, includingwater bodies contaminated by the past radiation accidents. The

þ7 48439 40910.v).

All rights reserved.

objective of this study is comparative analysis of dose rates toaquatic biota from the water bodies (Russia and former USSR),affected by the accidental or chronic radioactive contamination:Chernobyl NPPs Cooling Pond; Lake Uruskul (Southern Ural, Rus-sia), which is located in the territory of the Eastern Urals Radioac-tive Trace; Techa River (Southern Ural) and Yenisei River, which islarge river, located in Central Siberia. Results of the dose assess-ment were placed to the “dose rate e effects” scale and werecompared with some literature data on the radiobiological effectsin fish from the considered water bodies.

2. Materials and methods

2.1. Description of aquatic ecosystems

2.1.1. Chernobyl NPPs cooling pondThe Chernobyl NPP was located in the eastern part of Ukraine,

on the bank of the Pripyat River, which flows down to the KievReservoir. Water was supplied to the Chernobyl NPP from a coolingpond which was located southeast of the plant site and which wasmade by cutting off part of the river flood plain with a dam. Surfaceof the cooling pond was 21.7 km2, volume 150 $ 106 m3, averagedepth 6.6 m, maximum depth 20 m. The Chernobyl NPPs coolingpond was one of the most contaminated water bodies on theterritory affected by the Chernobyl accident. Primary radioactive

A.I. Kryshev, T.G. Sazykina / Journal of Environmental Radioactivity 108 (2012) 9e1410

contamination of the cooling pond as a result of the Chernobylaccident was due mainly to atmospheric fallout from 26 April 1986through May of 1986. All accidental radionuclides in the coolingpond can be subdivided into three groups: short-lived with half-lives less than several days (132I, 133I, 135I, 132Te, 239Np, 99Mo,140La), radionuclides with half-lives from several days to 2 months(131I, 140Ba, 136Cs, 141Ce, 103Ru, 95Zr, 95Nb, 89Sr) and relatively long-lived radionuclides (137Cs, 134Cs, 90Sr, 106Ru, 144Ce).

In May 1986 radioactive contamination of water of the coolingpond was determined mainly by 131I (15 kBq/L), 140Ba (1.1 kBq/L),95Zr, 95Nb, 137Cs (0.4 kBq/L), 144Ce, 106Ru. During the followingmonths radioactivity of water exponentially decreased due toradioactive decay and deposition of radionuclides to the bottomsediments. Activity concentrations of 137Cs in non-predatory fishin 1986e1990 varied in range 20e250 kBq/kg ww, in predatoryfish 110e300 kBq/kg (Kryshev and Sazykina, 1994; BIOMOVS,1996; Kryshev, 1998; Kryshev and Ryabov, 2000; Kryshev et al.,2003).

2.1.2. Lake Uruskul (Southern Ural)Small lake Uruskul is situated in Southern Ural, Chelyabinsk

Region of Russia, within the territory of the Eastern-Ural radio-active trace (EURT). The formation of this trace was caused bya radiation accident (29 September 1957) at the storage of liquidradioactive wastes PA “Mayak” (‘Kyshtym accident’). As a result ofthis accident, 7.4 $ 1016 Bq were dispersed over the territory of theSouthern Ural. The initial isotopic composition of the accidentalrelease was dominated by the relatively short-lived radionu-clides: 144Ce, 144Pr, 95Zr, 95Nb. However, the long-term radio-ecological situation in the region was determined by long-lived90Sr (2.7% of the total released activity) (Nikipelov et al., 1990;Kryshev, 1997).

Contamination of the lake was caused by the initial atmosphericdeposition of radionuclides on the water surface followed bysurface runoff of radionuclides from the catchment. The totalactivity of 90Sr in Lake Uruskul (September 1957) was estimated tobe equal to 6.7 $1013 Bq; in 1958 the activity concentration of 90Sr inwater of lake Uruskul was 8.7 kBq/L (Kryshev et al., 2001). LakeUruskul is one of the most contaminated lakes of EURT and still isprohibited for any economic activity. The measured activityconcentrations of 90Sr in bones of fish from the lake Uruskuldecreased from 2 $ 104 kBq/kg in 1958e1959 to 110 kBq/kg in 1992,the estimated whole-body concentrations of 90Sr in fish were about8e10 times lower (Kryshev et al., 2001; Kryshev, 2006).

2.1.3. Techa RiverTecha River is located in the Southern Urals (Russia) and is the

part of the large hydrological system Techae Isete Tobole Irtyshe

Ob belonging to the Kara Sea basin. Techa River is 243 km long, itsdepths varies from 0.5 to 2 km and the width is 15e30 m. TechaRiver was contaminated by technogenic radionuclides due todischarges from the PA “Mayak” mostly in 1949e1956. In thisperiod, about 1017 Bq of radionuclides entered the river ecosystem,including 1.2 $ 1016 Bq of 90Sr and 1.3 $ 1016 Bq of 137Cs (Kryshev andRyazantsev, 2010).

The most contaminated upper part of the river is overgrownwith aquatic plants. In the upper part of the river, the bogged areasalong the channel are contaminated with 90Sr and 137Cs. Theseswamps are currently the main source of radionuclides supply tothe river. At present, activity concentrations of 90Sr in water of theupper part of the Techa river are 5e20 Bq/L, in fish 100e3000 Bq/kgww, activity concentrations of 137Cs in water of the upper part ofthe Techa river (Muslyumovo) are 0.1e2 Bq/L, in fish 50e1000 Bq/kg (Kryshev et al., 1998; Ilyin and Gubanov, 2004; Kryshev andKryshev, 2005; Kryshev and Ryazantsev, 2010).

2.1.4. Yenisei RiverThe Yenisei is a large river situated in the Central Siberia (Rus-

sia). It flows northwards to the Yenisei Bay of the Kara Sea. Thelength of the Yenisei River is 3840 km, the average annual waterdischarge is 591 km3. Since 1958, the Yenisei River is contaminatedby the routine releases of radionuclides from the KrasnoyarskMining and Chemical Industrial Complex (KMCIC), which is locatedat a distance approximately at 2200 km from the river delta. Duringthe period of maximum activity, the industrial complex includedtwo commercial straight-through nuclear reactors, and one reactorwith a closed loop. In 1992, the straight-through reactors wereremoved from operation, which resulted in a considerable reduc-tion of radioactive contamination of the Yenisei River (Vakulovskyet al., 1995, 2004; Kryshev and Ryazantsev, 2010).

Among the radionuclides presented in liquid discharges fromthe KMCIC, 32P was of major radioecological importance, since itwas easily assimilated by the river biota. 32P is a short-livedradionuclide with T1/2 ¼ 14 days. The measured activity concen-trations of 32P in water of the Yenisei river, 10 km downstream theKMCIC in 1987e1991 were 7.4e9.8 Bq/L, in 1993e1997 0.1e0.5 Bq/L. Activity concentrations of 32P in the Yenisei fish caught5e25 km downstream the KMCIC in 1990 varied in range0.4e48 kBq/kg ww, in 2001 0.1e0.3 kBq/kg ww (Vakulovsky et al.,2004).

Ichthyofauna of the Yenisei River may be subdivided into twoecological groups: non-migratoryandmigratoryfish.Non-migratoryspecies normally travel only within limited distances (tens of kilo-meters), while migratory fish spend the most part of their life in theYenisei delta, inlet or bay, and go upstream the Yenisei River forspawning. Spawning grounds for many species of migratory fish aresituated in the middle reaches of the Yenisei River at the distances400e1600 km upstream the river mouth, i.e. at 600e1800 kmdownstream the source of radionuclide discharges (KMCIC).

2.2. Selection of the reference organisms

Radioecological assessment for all species inhabiting the naturalecosystems is too complex task to be performed. More realistic wayis to consider a limited number of typical species or ecologicalgroups for a particular water body, which could be used as therepresentative organisms for the radioecological study. ICRP hasdeveloped a set of formal reference species, which proposed to beused in radioecological assessment (ICRP, 2009). But for thedetailed estimates a concept of selection of the region-specificreference organisms seems to be more applicable. The followingbasic criteria for selection of the reference species of aquatic biotawere formulated (EPIC, 2003):

� Ecological (position in the ecosystem);� Availability for the radiation monitoring;� Dosimetric (critical pathways of exposure);� Radiosensitivity of organisms;� Population’s ability to self-recovery from the effects of ionizingradiation.

2.2.1. Ecological criteriaEcological criteria recommend selection of reference organisms

among the dominating species on the trophic levels of ecosys-tems. Dominating species are responsible for the major energy/biomass fluxes in ecosystems, normal vital functions of thedominating species are necessary for functioning of the wholeecosystem (Sazykina et al., 2000). In general, one or two domi-nating species are representative for one trophic level of anaquatic ecosystem.

A.I. Kryshev, T.G. Sazykina / Journal of Environmental Radioactivity 108 (2012) 9e14 11

2.2.2. Availability for radiation monitoringThis criterion takes into account necessity of regular measure-

ments of the radionuclides activity concentrations in referencespecies. Therefore, it could be recommended to select the referenceaquatic organisms with the following characteristics:

� Typical, large in number species with broad natural habitatarea;

� Species can be easily collected for the radiation monitoringpurposes;

� Species can be easily identified;� Organisms with high concentration factors of radionuclides;� Species of commercial or other importance for humans.

In most cases the dominating organisms, selected using theecological criteria, are appropriate for radiation and ecologicalmonitoring. Organisms with high concentration factor of radionu-clides are useful for radioecological studies because they demon-strate the highest levels of biological transfer of technogenicradioactivity. However, microorganisms (phytoplankton, bacteria,etc.) do not satisfy the criterion of availability for radiation moni-toring, because of their small size, difficulties of sampling andidentification. Rare species also inappropriate for the permanentradiation monitoring because their catching for measurementscould led to unwarrantable ecological damage.

2.2.3. Dosimetric criteriaIt is proposed to select the reference species of biota on the basis

of analysis of the critical pathways of radiation exposure to biota.The following exposure pathways should be considered in aquaticecosystems:

� Internal exposure from radionuclides incorporated in organsand tissues of aquatic organisms;

� External exposure from radionuclides in water;� External exposure from radionuclides deposited in bottomsediments.

Therefore, it is advisable to select the reference species amongthe ‘critical groups’ for the major exposure pathways. In aquaticecosystems they are the following:

� Benthic organisms (critical group for the exposure from bottomsediments);

� Organisms with high bioaccumulation of technogenic radio-nuclides, presented in the studied water body (critical groupfor the internal exposure).

2.2.4. Radiosensitivity criteriaIt is proposed to select the reference species among radiosen-

sitive species in ecosystem and to exclude from considerationradioresistant organisms. Different components of hydrobiocenosis

Table 1Reference species of aquatic biota in the studied water bodies.

Ecological group Chernobyl NPPs cooling pond Lake Uruskul

Pelagic fish Silver carp(Hypophthalmichthys molitrix)

Goldfish (Carassius c

Benthic fish Bream (Abramis brama) Carp (Cyprinus carpiPredatory fish Pike-perch (Stizostedion lucioperca) e

Migratory fish e e

Mollusks Gastropoda (Viviparus contectus) Gastropoda (LymnaeAquatic plants Potamogeton perfoliatus Typha sp.

demonstrate considerable differences in their sensitivity to ionizingradiation. For example, many populations of primitive organismsare resistant to irradiation. In aquatic ecosystems, bacteria,plankton and some invertebrates are by orders of magnitude lesssensitive to irradiation comparing with fish or near-water birds.Selection of reference species among radioresistant groups oforganisms is not appropriate for assessment.

2.2.5. Ability of populations to self-recoveryIn general, the reproduction potential of populations depends

on the number of offsprings per unit time and on the period ofreaching the reproductive maturity. The species with very highreproductive potential (for example, microorganisms) are notconsidered as the reference organisms for the radioecologicalassessment. If populations of such species damaged by radiation,they easily recover by reproduction of remaining organisms. Incontrary, the species with relatively low reproductive rates shouldbe considered as candidates for the reference species for radio-ecological assessment.

Taking into account the above-mentioned criteria, the followingecological groups of organisms were selected as the reference foraquatic ecosystems:

� Pelagic fish� Benthic fish� Mollusks� Aquatic plants� Near-water birds and mammals.

The described methodology was applied to indicate the refer-ence species for radioecological assessment in the consideredwater bodies: Chernobyl NPPs cooling pond, Lake Uruskul, Techaand Yenisei Rivers. The specific biological organisms (species) wereselected from these ecological groups for every studied water body.Ecological groups and selected reference species of biota for thesewater bodies are presented in Table 1.

2.3. Dose rate calculations

Dose rates to the reference organisms were calculated takinginto account their morphometric and ecological characteristics, asa sum of internal and external exposure (from water and bottomsediments). Dose rates from the incorporated b-emitting radionu-clides were calculated as the dose rates within the infinite volumeof an absorbing material uniformly contaminated with alpha andbeta emitter (Db

N, Gy/day):

DNb ¼ 1:38,10�8,Eb,y; (1)

where Eb are the average energies of b-particles per decay of theparticular radionuclide, MeV, and y is the activity concentration ofthe radionuclide in the aquatic organism, Bq/kg ww.

Techa River Yenisei River

arassius) Goldfish (Carassius carassius) Dace (Leuciscus leuciscus)

o) Roach (Rutilus rutilus) Roach (Rutilus rutilus)Pike (Esox lucius) Pike (Esox lucius)e Cisco (Coregonus lavaretus)

a stagnalis) Bivalvia (Anodonta) Bivalvia (Anodonta)Potamogeton sp. Elodea canadensis

A.I. Kryshev, T.G. Sazykina / Journal of Environmental Radioactivity 108 (2012) 9e1412

Contribution of g-radiation to the internal dose rate Dgint (Gy/

day) was calculated by the formula (Blaylock et al., 1993; Kryshevet al., 2002):

Dintg ¼ 1:38,10�8,Corg,Eg,ng,F

�Eg

�; (2)

where Corg - activity concentration of radionuclide in aquaticorganism; Eg is the photon energy emitted during transition froma higher to a lower energy state, MeV; ng is the proportion ofdisintegrations producing a g-ray; F(Eg) is the fraction of energy Eg(MeV) absorbed within the organism (Blaylock et al., 1993).

The external dose rate to aquatic organisms from radionuclidesin water was calculated by the formula:

Dextg ¼ DN

g � Dintg ; (3)

where DNg ¼ 1:38,10�8,Eg,ng,Cwat; only g-exposure was

considered for evaluation of the external dose rates to aquaticorganisms.

The external exposure from the contaminated bottom sedi-ments was calculated by representing of them as a layer of finitethickness h, only exposure from g-emitters was taken into account.The dose rate at the surface of bottom sediments was calculatedwith the following formula (Jaeger et al., 1968; Mashkovich, 1982;Gusev et al., 1989; Kryshev et al., 2002):

Dsedg;extðhÞ ¼ 0:5,Dsed

g ðNÞ,�1� E2

�msedeff ,h

��,ssed; (4)

where Dsedg;extðhÞ is the dose rate at the surface of bottom sediments,

Gy/day; h is the thickness of the layer of sediments, cm; ssed is theportion of time, which the organism spends at the bottom sedi-ments; Dsed

g ðNÞ is the dose rate in a sediment layer of infinitethickness with a uniformly distributed gamma-emitter, Gy/day;msedeff is the linear attenuation coefficient of g-radiation, whichdepends on the material of sediments; E2(x) is the integral expo-nential function (Mashkovich, 1982):

E2ðxÞ ¼ xZ N

x

expð�yÞy2

dy ¼Z 1

0expð�x=yÞdy: (5)

2.4. Results and discussion

Table 2 shows the comparative estimates of dose rates to thereference biota species of the Chernobyl NPPs cooling pond, LakeUruskul, Techa and Yenisei Rivers. For each considered water bodythe dose assessment has been made for two radioecological

Table 2Comparative estimates of average dose rates for the reference species of aquatic biota, m

Ecological group Water body

Chernobyl NPPscooling pond 1986 (1996)

Lake Uruskul1957e1958 (199

Aquatic plants 15.0 � 7.0 8.0 � 3.0(0.10 � 0.03) (0.05 � 0.02)

Mollusks 34.0 � 11.0 85.0 � 25.0(0.8 � 0.2) (0.3 � 0.2)

Pelagic fish 13.0 � 4.0 35.0 � 17.0(0.04 � 0.01) (0.2 � 0.1)

Benthic fish 22.0 � 9.0 55.0 � 27.0(0.20 � 0.07) (0.2 � 0.1)

Predatory fish 12.0 � 5.0 e

(0.09 � 0.04)Migratory fish e e

situations: early period of contamination (maximum dose rates)and late period (long-term chronic dose rates). Calculations of doserates were performed using the measured activity concentrationsin components of aquatic ecosystems. Model reconstruction on thebasis of the ECOMOD model was applied if the data were scarce ornot available (Kryshev, 1998; Kryshev and Ryabov, 2000; Kryshev,2004, 2006). The external dose rate estimates for the benthic fishfrom the Chernobyl NPPs cooling pond were compared with thedata of direct radiometry, which was performed in 1989 by Lystsovet al. (1990). The calculated value for this period (1.1 mGy/day) fallinto the measured range 0.1e2 mGy/day. Dose rates to biota of theTecha River in the early period of contamination (1950e1951) wereestimated by Kryshev and Ryazantsev (2010).

Analysis of the dose rate estimates presented in Table 2 showsthe considerable differences in exposure to biota during the earlyand chronic period of radioactive contamination of all consideredwater bodies. Differences between the dose rates to hydrobionts ofthe Chernobyl NPPs cooling pond in 1986 and 1996 were from 40times (mollusks) to 300 (pelagic fish), in Lake Uruskul from 160(aquatic plants) to 280 (benthic fish), in Techa River from 100(benthic fish) to 1600 (aquatic plants). This relationship was causedby the presence of short-lived radionuclides in the early period ofcontamination of thesewater bodies. In the specific cases the short-lived radionuclides were permanent contributors to the biotaexposure, for example, 32P in the Yenisei River. Decrease of doserates to the Yenisei biotawere caused by the considerable reductionof 32P discharges to the river. Dose rates to biota and radioecologicalconsequences of the radionuclides intake to rivers depends on thesize of water bodies, the highest dose rates to biota were in therelatively small Techa River, the lowest dose rates to aquaticorganisms were in the large Yenisei River.

The most vulnerable component of aquatic ecosystems was thebenthic food chain. According to our estimationsmollusks obtainedthe highest dose rates among all reference species in all consideredwater bodies, both in early and late periods of radioactivecontamination. In the relatively less flowing water bodies, such asChernobyl NPPs cooling pond and Lake Uruskul, dose rates to thenear-bottom fauna were 60e70% higher than exposure of thepelagic species. Vulnerability of the benthic species was caused bythe additional external exposure from the highly contaminatedbottom sediments, and increased values of concentration factors of90Sr and 32P in mollusks and benthic fish in comparison with thepelagic species. At the early period of aquatic contamination afterradiation accidents aquatic plants obtained high doses, becausethey intensively adsorbed several short-lived radionuclides (144Ce,95Zr, 95Nb 106Ru, 140Ba) on their surface with high concentrationfactors (Kryshev et al., 2003). As one can see in Table 2, the dose

Gy/day.

2)Techa River1951e1952 (1990e1998)

Yenisei River1990e1991 (2000e2001)

83.0 � 62.0 6$10�2 � 3$10�2

(0.05 � 0.02) (1$10�3 � 5$10�4)80.0 � 50.0 0.2 � 0.1(0.8 � 0.3) (3$10�3 � 1$10�3)30.0 � 15.0 5$10�2 � 2$10�2

(0.10 � 0.04) (8$10�4 � 4$10�4)30.0 � 15.0 5$10�2 � 2$10�2

(0.30 � 0.12) (8$10�4 � 4$10�4)30.0 � 15.0 3$10�2 � 1$10�2

(0.30 � 0.15) (7$10�4 � 3$10�4)e 2$10�3 � 8$10�4

(5$10�5 � 2$10�5)

Fig. 2. Dose rates to the benthic fish species placed to the ‘dose rates e effects’ scale:I e no negative effects on fish; II e negative effects on the fish morbidity; III e negativeeffects on the reproduction system of fish; IV e effects on life shortening; V e increaseof the fish mortality and depression of fish populations.

A.I. Kryshev, T.G. Sazykina / Journal of Environmental Radioactivity 108 (2012) 9e14 13

rates to migratory fish in Yenisei River were by the order ofmagnitude lower than to the other fish species, because themigratory fish spent most part of the life far away from the sourceof discharges and did not feed during the spawning migrations.

Fish is known to bemost radiosensitive among the poikilotermicaquatic animals. On the organisms’ level the following groups ofeffects are important for survival of populations: effects onmorbidity decrease of reproduction and life shortening (FASSET,2003). Data published in Russian and the former Soviet Unionconcerning the effects of ionizing radiation on non-human biotawere compiled within the framework of the EC EPIC Project“Environmental Protection from Ionizing Contaminants in theArctic”, where emphasis was placed on the effects of chronic/life-time radiation exposure (Sazykina and Kryshev, 2003; Kryshevet al., 2008). The following numerical ‘dose rates e effects’ scalewas proposed for fish living in the northern/temperate climate:

� Dose rate 1 mGy d�1 is the threshold level for appearance offirst negative changes in fish immune system; at lower doserates the organisms seemingly can adapt for radiation withgradual restoration of health parameters;

� Dose rates 5e10 mGy d�1 are threshold levels for developmentof negative effects on reproduction system;

� Dose rates higher than 10mGy d�1 of chronic lifetime exposurelead to life shortening of adult fish;

� Dose rates higher than 20 mGy d�1 lead to significant increaseof mortality and decrease of fish population.

Results of the dose rates calculations for the reference species offish from the Chernobyl NPPs cooling pond, Lake Uruskul, Techaand Yenisei Rivers were placed on this ‘dose rate e effects’ scale.Fig. 1 shows such comparison for pelagic fish and Fig. 2 for benthicfish from the considered water bodies.

Dose rates to fish in the Chernobyl NPPs cooling pond in 1986were estimated to be 12 mGy/day for silver carp (pelagic fish) and22 mGy/day for bream (benthic fish); after 1986 the dose rates tofish gradually decreased. So the effects on the reproduction systemof silver carp and some depression of bream population in thiswater body can be anticipated (Fig. 1). Data of radiobiologicalstudies confirmed the presence of radiation effects on the repro-duction system of silver carps from the Chernobyl NPPs cooling

Fig. 1. Dose rates to the pelagic fish species placed to the ‘dose rates e effects’ scale:I e no negative effects on fish; II e negative effects on the fish morbidity; III e negativeeffects on the reproduction system of fish; IV e effects on life shortening; V e increaseof the fish mortality and depression of fish populations.

pond. As it was reported by Belova et al. (1993) and Makeyeva et al.(1994) in 1989e1992 7.1% of studied silver carps in this water bodywere sterile, 35% females and 48% males of silver carps haddifferent anomalies of gonads. In natural conditions sterility ofsilver carps is rare (less than 0.25%). Unfortunately, we did not findany literature data concerning the radiation effects in benthic fishfrom the Chernobyl NPPs cooling pond.

Dose rates to fish in Lake Uruskul during the first years ofcontaminationwere estimated to be 35e55mGy/day. At these doserates the effects on life shortening of fish can be anticipated,especially during the early period of the lake contamination. In1970s Voronina et al. (1977) reported significant changes in the agestructure of goldfish population in Lake Uruskul, resulting theconsiderable decrease or even elimination of specimens from oldage classes.

Dose rates to fish in the Yenisei River were below thresholdvalue 1 mGy/day during all considered period. No radiobiologicaleffects on fish were reported in literature for the Yenisei River. Atpresent, dose rates to the reference fish species in the studied riversvary from 5 $ 10�5 e 8 $ 10�4 mGy/days (Yenisei) to 0.2e0.3 mGy/day (Techa). It can be concluded, that the current levels of fishexposure in the Techa and Yenisei Rivers do not lead to any negativechanges in the fish organisms and populations.

3. Conclusions

Dose assessment was performed for the reference species ofaquatic biota from the Chernobyl NPPs cooling pond, Lake Uruskul(EURT), Techa and Yenisei Rivers. The exposure levels to aquaticbiota in the early period of radiation accidents were high enough tocause radiobiological effects on the fish reproduction system(Chernobyl NPPs cooling pond) and the fish life shortening (LakeUruskul). The most vulnerable component of freshwater ecosystemwas benthic food chain. Current dose rates to biota in all consideredwater bodies are below the radiation safety level of 1 mGy/day. The‘dose rates e effects’ relationships for the chronic exposure of biotacan be used to evaluate the permissible levels of the radionuclidesactivity concentrations in water, bottom sediments and biota,which ensure radiation safety of the most sensitive organisms andpopulations.

A.I. Kryshev, T.G. Sazykina / Journal of Environmental Radioactivity 108 (2012) 9e1414

References

Belova, N.V., Verigin, B.V., Yemeljanova, N.G., Makeyeva, A.P., Ryabov, I.N., 1993.Radiobiological analysis of silver carp Hypophthalmichthys molitrix in thecooling pond of the Chernobyl NPP in the post-accidental period. I. Thecondition of the reproductive system of fish survived the accident. VoprosyIchthyologii (Problems of Ichthyology) 33 (6), 814e828 (in Russian).

BIOMOVS II: Model testing using Chernobyl data, 1996. Assessment of the Conse-quences of the Radioactive Contamination of Aquatic Media and Biota. Tech-nical Report N 10. Swedish Radiation Protection Institute, Stockholm.

Blaylock, B.G., Frank, M.L., O’Neal, B.R., 1993. Methodology for Estimating RadiationDose Rates to Freshwater Biota Exposed to Radionuclides in the Environment.ES/ER/TM-78. ORNL, Oak Ridge, TN USA.

Brown, J.E., Alfonso, B., Avila, R., Beresford, N.A., Copplestone, D., Pröhl, G.,Ulanovsky, A., 2008. The ERICA tool. Journal of Environmental Radioactivity 99(9), 1371e1383.

Doe: US Department of Energy, 2002. A Graded Approach for Evaluating RadiationDoses to Aquatic and Terrestrial Biota DOE Technical Standard, DOE-STD-115.

EPIC - Environmental Contamination from Ionising Contaminants in the Arctic,2003. Final Report. Project ICA2-CT-2000e10032. Norwegian RadiationProtection Authority.

FASSET: EC Project on Radiation Effects on Plants and Animals (FIGE-CT-2000-00102), 2003. Deliverable 4, edited by D. Woodhead and I. Zinger.

Garnier-Laplace, J., Gilbin, R. (Eds.), 2006. Derivation of Predicted-No-Effect-Dose-Rates Values for Ecosystems (and their Sub-Organizational Levels) Exposed toRadioactive Substances Deliverable 5 of the EC ERICA Project (FI6R-CT-2004e508847).

Gusev, N.G., Klimanov, V.A., Mashkovich, V.P., Suvorov, A.P., 1989. Physical Funda-mentals for Protection from Ionizing Radiation, vol. 1. Energoatomizdat, Mos-cow, 512 pp. (in Russian).

ICRP: International Commission on Radiological Protection, 2009. Environmentalprotection: the concept and use of reference animals and plants. Annals of theICRP Publication 108.

Ilyin, L.A., Gubanov, V.A. (Eds.), 2001. Heavy Radiation Accidents: Consequences AndCountermeasures. IzdAT, Moscow, 752 pp. (in Russian).

Jaeger, R.G., Blizard, E.P., Chilton, A.B., Grotenhuis, M., Hönig, A., Jaeger, T.A.,Eisenlohr, H.H. (Eds.), 1968. Engineering Compendium on Radiation Shielding.Shielding Fundamentals and Methods, vol. 2. Springer-Verlag, Berlin.

Kryshev, I.I. (Ed.), 1997. Environmental Risk Analysis for the Ural RadioactivePattern. Russian Nuclear Society, Moscow.

Kryshev, A.I. Modelling of accidental radioactive contamination and assessment ofdoses to biota of the Chernobyl NPPs cooling pond, 1998. In: Proceedings of theTopical Meeting of International Union of Radioecologists, Mol (Belgium), 1 e 5June 1998. Balen, BVG, p. 32 e 38.

Kryshev, A.I., 2004. Evaluation of the biological transfer of 32P, 137Cs and 65Zn by fishin the Yenisei river. The Science of the Total Environment 322 (1e3), 191e207.

Kryshev, A.I., 2006. 90Sr in fish: a review of data and possible model approach. TheScience of the Total Environment 370 (1), 182e189.

Kryshev, A.I., Kryshev, I.I., 2005. Estimation of dose and radiation risk for pike (Esoxlucius) in the river system Techa e Ob. In: Proceedings of the 2nd InternationalConference on Radioactivity in the Environment, Nice (France), 2 e 6 October2005. Østerås (Norway), NRPA, p. 150 e 153.

Kryshev, A.I., Ryabov, I.N., 2000. A dynamic model of 137Cs accumulation by fish ofdifferent age classes. Journal of Environmental Radioactivity 50 (3), 221e233.

Kryshev, I.I., Ryazantsev, E.P., 2010. Ecological Safety of the Nuclear Energy Complexof Russia, second ed. IzdAT, Moscow, 496 pp. (in Russian).

Kryshev, I.I., Sazykina, T.G., 1994. Accumulation factors and biogeochemical aspectsof migration of radionuclides in aquatic ecosystems in the areas impacted bythe chernobyl accident. Radiochimica Acta 66/67, 381e384.

Kryshev, I.I., Romanov, G.N., Chumichev, V.B., Sazykina, T.G., Isaeva, L.N.,Ivanitskaya, M.V., 1998. Radioecological consequences of radioactive dischargesinto the Techa River on the Southern Urals. Journal of Environmental Radio-activity 38 (2), 195e209.

Kryshev, I.I., Romanov, G.N., Isaeva, L.N., Kryshev, A.I., Kholina, Y.B., 2001. Radio-ecological state of lakes in the territory of the Eastern Urals radioactive trace. In:Trapeznikov, A.V., Vovk, S.M. (Eds.), Problems of Radioecology and BoundaryDisciplines, vol. 4. Technocentre, Zarechny, pp. 107e122 (in Russian).

Kryshev, A.I., Sazykina, T.G., Strand, P., Brown, J.E., 2002. Radioecological model fordose estimation to Arctic marine biota. In: Proceedings of the 5th InternationalConference on Environmental Radioactivity in the Arctic and Antarctic. St.Petersburg, 16 e 20 June 2002. NRPA, Norway, p. 326 e 329.

Kryshev, I.I., Sazykina, T.G., Kryshev, A.I., 2003. The chernobyl accident and aquaticbiota. In: Scott, M. (Ed.), Modelling Radioactivity in the Environment. ElsevierScience Ltd., Oxford, pp. 391e416.

Kryshev, A.I., Sazykina, T.G., Sanina, K.D., 2008. Modelling of effects due to chronicexposure of a fish population to ionizing radiation. Radiation and Environ-mental Biophysics 47 (1), 121e129.

Makeyeva, A.P., Yemeljanova, N.G., Belova, N.V., Ryabov, I.N., 1994. Radiobiologicalanalysis of silver carp Hypophthalmichthys molitrix in the cooling pond of theChernobyl NPP in the post-accidental period. II. Development of the repro-ductive system of the fish in the 1st generation. Voprosy Ichthyologii (Problemsof Ichthyology) 34 (5), 681e696 (in Russian).

Mashkovich, V.P., 1982. Protection from Ionizing Radiation (Handbook). Ener-goatomizdat, Moscow. 296 p. (in Russian).

Nikipelov, B.V., Mikerin, Y.I., Romanov, G.N., Spirin, D.A., Kholina, Y.B., Buldakov, L.A.,1990. The radiation accident in southern ural in 1957 and liquidation of itsconsequences. Proceedings of International Symposium, Vienna, 6e10November 1989. IAEA-SM-316/55. Vienna, IAEA, p. 373e403.

Sazykina, T.G., Kryshev, A.I., 2003. EPIC database on the effects of chronic radiationin fish: Russian/FSU data. Journal of Environmental Radioactivity 68 (1), 65e87.

Sazykina, T.G., Alekseev, V.V., Kryshev, A.I., 2000. The self-organization of trophicstructure in ecosystem models: the succession phenomena, trigger regimes andhysteresis. Ecological Modelling 133, 83e94.

Sazykina, T.G., Kryshev, A.I., Sanina, K.D., 2009. Non-parametric estimation ofthresholds for radiation effects in vertebrate species under chronic low-LETexposures. Radiation and Environmental Biophysics 48 (4), 391e404.

Ulanovsky, A., Pröhl, G., 2008. Tables of dose conversion coefficients for estimatinginternal and external radiation exposures to terrestrial and aquatic biota.Radiation and Environmental Biophysics 47 (2), 195e203.

UNSCEAR: United Nations Scientific Committee on the Effects of Atomic Radiation,1996. Effects of Radiation on the Environment. Report to the General Assembly.Annex to Sources and Effects of Ionizing Radiation New York.

Vakulovsky, S.M., Kryshev, I.I., Nikitin, A.I., Savitsky, Y.V., Malyshev, S.V.,Tertyshnik, E.G., 1995. Radioactive contamination of the Yenisei River. Journal ofEnvironmental Radioactivity 29 (3), 225e236.

Vakulovsky, S.M., Kryshev, A.I., Tertyshnik, E.G., Chumichev, V.B., Shishlov, A.E.,Savitsky, Y.B., Koudinov, K.G., 2004. Accumulation of 32P in the Yenisei fish andreconstruction of doses to human population. Atomic Energy 97 (1), 61e67 (inRussian).

Vives i Batlle, J., Balonov, M., Beaugelin-Seiller, K., Beresford, N., Brown, J., Cheng, J.-J.,Copplestone, D., Doi, M., Filistovic, V., Golikov, V., Horyna, J., Hosseini, A.,Howard, B., Jones, S., Kamboj, S., Kryshev, A., Nedveckaite, T., Olyslaegers, G.,Pröhl, G., Sazykina, T., Ulanovsky, A., Vives Lynch, S., Yankovich, T., Yu, C., 2007.Inter-comparison of absorbed dose rates for non-human biota. Radiation andEnvironmental Biophysics 46 (4), 349e373.

Voronina, E.A., Peshkov, S.P., Shekhanova, I.A., 1977. Biological indices of chronicallyexposed populations of goldfish. In: Radioecology of Animals. Proceedings ofthe 1st All-Union Conference. Nauka, Moscow, pp. 71e73. (in Russian).