1environment Radioactivity and the · 2011. 7. 6. · 16 2008 Scientific and Technical Report - IRSN T he subjects covered in this report reflect IRSN’s scientific achievements

14 2008 Scientific and Technical Report - IRSN

Radioactivityand the environment1

IRSN - 2008 Scientific and Technical Report 15

1 RADIOACTIVITY and the environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

1.1 ENVIRHOM’S "ENVIRONMENTAl" THEME: A better understanding of the ecological consequences of chronic exposure to low-level radionuclides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

newsflashnewsflashnewsflashnewsflashnewsflashnews

1.2 TAkINg INTO ACCOuNT INTERACTIONS between radioactive substances and chemical substances to improve ecological risk assessment in

a multipollution context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

1.3 THE SAlIFA PRIMEQuAl PROjECT: A study on dry deposition of aerosols in an urban environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

1.4 CONTRIBuTIONS OF ARTIFICIAl ATMOSPHERIC RADIONuClIDE MONITORINg to the study of transfer processes and the characterization of post-accidental situations . . 37


1.5 "ATMOSPHERIC AEROSOl wASHOuT AND ClEANINg" CAMPAIgN (Puy-de-Dôme): characterization of atmospheric radioactivity at three sites located at different altitudes . . . 45

1.6 IMPlEMENTATION OF THE ARgOS ExPERIMENTAl PlATFORM for the assessment and characterization of IRSN environmental radioactivity measurement instruments . . 47

1.7 MAPPINg PRIORITY zONES for radon risk control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49


1.8 MAPPINg lAND uSE AROuND NuClEAR SITES for assessment of radiological and health impact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

1.9 SYMBIOSE: Simulation and modeling of radiological risks to human health and the environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

1.10 CREATION OF THE TRASSE NATIONAl RESEARCH gROuP as part of the PACEN program (CNRS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

1.11 FOlIAR TRANSFER OF RADIONuClIDES IN THE BIOSPHERE: A study conducted in Chernobyl in collaboration with Andra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

1.12 MEDIuM PROjECT: Study of sediment mixing and dispersion using particulate markers in the Seine estuary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

1.13 RADIOACTIVITY IN ORgANISMS of deep-sea hydrothermal sites . . . . . . . . . . . . . . . . . . . . . . . . . . 70

1.14 kEY EVENTS and dates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72


The subjects covered in this report reflect IRSN’s scientific achievements in three key areas of environmental risk assessment:acquiring a better understanding of how chronic exposure to

radionuclides affects ecosystems;

gaining knowledge on the behavior of aerosols dispersed in the

atmosphere and their interaction with soil surfaces;

more accurately predicting the risks of radon concentration in

housing.

Ecological consequences of chronic exposure to radi-onuclidesFor several years now, IRSN has been developing experimental

research programs to improve the scientific bases of the interna-

tional radiation protection system, with particular emphasis on

the ecological and health impact of chronic environmental expo-

sure to radionuclides, within the framework of the ENVIRHOM

research program. A preliminary exploratory research phase com-

pleted in 2007, using "reference" models of chronic exposure of

humans and the environment to uranium, led to the identification

of multiple, sometimes unexpected effects for a broad range of

biological and physiological functions (reproduction, growth,

behavior, etc.).

The article by Adam et al ("ENVIRHOM’s Environmental theme:

A better understanding of the ecological consequences of chron-

ic exposure to low-level radionuclides"), provides an overview of

the results obtained since 2001 in the Environmental part of this

program, focusing on the biological effects observed in various

biological models representative of the aquatic environment

(crustaceans, mollusks, insects, fish) under controlled conditions

of chronic uranium exposure.

This experimental approach is, of course, highly simplistic with

regard to the diversity and complexity of ecosystems and the

multitude of stress factors possibly affecting them. Nevertheless,

contributes to understanding the significant elementary effects

associated with the presence of radionuclides in the environment.

The effects observed at the individual level on fundamental bio-

logical processes provide more accurate information on the "life

history traits" of the species studied, particularly reproductive

capacity and somatic growth, which are essential to population

dynamics. This information is used to determine the concentrations

at which radionuclides have no impact on all or part of the eco-

systems studied, thereby serving as the basis for environmental

risk characterization.

This research has also led to the identification of subcellular

"biomarkers" sensitive to the presence of uranium in the environ-

ment. The biological responses observed are not necessarily

indicative of damage to species or ecosystems, but they can be

used to study the main mechanisms involved during uranium

exposure, in conjunction with the Human Health part of the

ENVIRHOM research program.

Didier CHAMPIONEnvironment and Response

RADIOACTIVITY and the environment


spheric activity, and the importance of wet deposition. The data

obtained is closely representative of the general behavior of

radionuclides dispersed in the atmosphere in the form of par-

ticles, and therefore relevant for developing new atmospheric

radioactivity monitoring networks and for assessing the impact

of accident release over long distances.

In the case of depositions in urban areas, one of the main interests

of the studies conducted by IRSN in collaboration with various

research partners lies in improving the ability to predict the impact

of accidental release in urban environments, particularly with

regard to radiation protection. The results obtained during the

various tracing and measurement campaigns clearly show the

complexity of dry deposition parameters, depending on the type

of deposition surface (with different results obtained for glass

surfaces and façade coatings). These results can be used to quantify

deposition rates for the different surfaces considered, and also to

demonstrate the interest of studying the influence of temperature

and micrometeorology near the deposition surface.

Reviewing the basis of "radon potential" mapsFor several years now, France has developed a radon exposure

control policy including systematic screening of public spaces in

"priority" districts. Thirty-one priority districts were identified on

the basis of bibliographic research campaigns conducted by IPSN

in collaboration with the French Ministry for Health. The objective

was to compile an exhaustive statistical database (over 12,000

measurements of radon concentrations in buildings) sufficiently

reliable to assess the potential exposure of populations through-

out the country. However, the use of these results for the devel-

opment of radon risk prevention strategies has progressively

revealed its limitations, particularly in the case of regions with a

These results generally show the possibility of developing strate-

gies to characterize the ecological status of contaminated eco-

systems. This type of approach is particularly useful for proposing

more relevant ecological risk assessment methods, particularly

through the development of scientifically founded extrapolation

tools. Based on these encouraging results, IRSN is conducting

similar studies with a view to extending current knowledge to

different types of organisms and other radionuclides of interest

(e.g. 241Am, 75Se, or even external exposure to γ radiation from 137Cs).

Behavior of atmospheric aerosolsUnderstanding and predicting the behavior of atmospheric

aerosols (fine radioactive particles suspended in the atmosphere)

and their interaction with soil surfaces has long been one of the

major areas of interest in assessing the environmental impact

of nuclear activities under normal operating conditions, and all

the more so under accident conditions.

Two articles are devoted to this research area: Masson et al,

"Contributions of artificial atmospheric radionuclide monitoring for

the study of transfer processes and the characterization of post-

accident situations", discusses the results of 50 years of radioactiv-

ity monitoring activities throughout France, with special emphasis

on the use of cesium-137, an artificial radionuclide released in the

past during nuclear tests and incidents. Maro et al, "The SaliFa

PRIMEQUAL Project: A study on dry deposition of aerosols in an urban

environment", focuses on dry aerosol deposition in urban areas.

Observations of cesium-137 activity concentration in the atmo-

sphere provide information on various relevant factors such as

the origin of air masses circulating over continental France,

resuspension mechanisms, impact of altitude on specific atmo-


France with a zoning scheme more accurate than the regional

district scale, and with a more objective representation of the

variability in radon exhalation potential at the soil surface. This new

map should provide a more accurate response to the needs of pub-

lic authorities in controlling radon risk.

This report illustrates how IRSN research activities can have an

operational impact on public policy, on the action of social actors

concerned by radon risk control in public spaces, on work places,

and eventually on private dwellings.

contrasted geological context or where the distribution of biblio-

graphic data is not homogeneous.

These past years, at the request of the French nuclear safety author-

ity, IRSN research regarding radon exhalation phenomena has been

used to develop a new approach to map priority zones for radon

risk control. The article by Ielsch et al ("Mapping priority zones for

radon risk control") discusses this research and the new method

proposed, which is currently being implemented by IRSN with a

view to establishing (by late 2009) a new radon potential map of


1. 1

This article presents the approach and ongoing progress of the

Environmental part of the ENVIRHOM research program. Uranium

has been the main target of the research program since it began in

2001. This has led to the development of the necessary tools to

determine biological effects under real or plausible exposure condi-

tions representative of contamination situations potentially encoun-

tered during nuclear fuel cycle activities under normal or accident

operating conditions (from mining activities to waste processing

and storage activities). Uranium was used to contaminate different

ecosystem compartments (water, sediments, soils) under controlled

conditions, and the resulting biological effects were determined for

a limited number of biological models representative of the bio-

logical diversity of the ecosystems (plants, crustaceans, mollusks,

insects, fish).

The most recent results concern the aquatic organisms discussed

in this article. Their interpretation benefits from the knowledge base

acquired since the ENVIRHOM research program began. Other

studies are also in progress with a view to extending this research

to other types of organisms (e.g. complex terrestrial plants) and

other radionuclides of interest, so as to consider different types of

radioactive emissions (e.g. 241Am, 75Se, 3H, or external γ irradiation with 137Cs).

Christelle ADAM-GUILLERMIN, Jean-Marc BONZOM, Stéphanie BOURRACHOT, Victor DIAS, Rodolphe GILBIN, Adélaïde LEREBOURS, Olivier SIMONRadioecology and Ecotoxicology Laboratory

Jacqueline GARNIER-LAPLACE Study of Radionuclide Behavior in Ecosystems Department

Frédéric ALONZOEnvironmental Modeling Laboratory

Chronic environmental contamination from low-activity radionuclides raises the question of assessing the poten-

tial consequences for humans and ecosystems. This assessment is confronted with insufficient scientific data and

the absence of proven methods that take into account the complexity of the processes involved.

Nevertheless, the future implementation of an environmental radiation protection system consistent with that

currently implemented for chemical substances (European Commission, 2003) requires the determination of

threshold levels above which exposure to radionuclides may induce damage to organisms and populations

constituting ecosystems, with the resulting ecological consequences. The ENVIRHOM research program aims

to address these issues by acquiring new scientific data concerning the effects of chronic radionuclide exposure

and identifying relevant markers through experiments on living organisms (complex vertebrates, fish, inverte-

brates, plants, etc.).

ENVIRHOM’S "ENVIRONMENTAl" THEME: A better understanding of the ecological consequences of chronic exposure to low-level radionuclides

1. 1


High sensitivity of early life stages (studies on Danio rerio)

The effects of radionuclides such as uranium were studied with respect

to the life history traits of several organisms representative of aquat-

ic ecosystems, such as monocellular algae, microcrustaceans (daphnia),

insects (chironomidae) and fish. Danio rerio (zebrafish) is a sort of

aquatic lab rat well suited for toxicological laboratory studies (main-

tainability of controlled conditions, brief life cycle, significant knowl-

edge regarding its physiology, well sequenced genome, etc.). The results

acquired with uranium show a particularly high sensitivity during the

early stages of fish development, from egg to larva [Bourrachot et al,

2008a]. The different stages of embryonic development are not

equally affected by uranium. Pre-eclosion embryos are protected by

the egg envelope (chorion), which prevents most of the metal in the

surrounding environment from entering the organism, whereas the

larval eclosion period is significantly affected by uranium concentra-

tions in water representative of contaminated sites such as those in

the immediate upstream vicinity of certain mining areas (uranium

concentrations of 20 µg per liter and higher), with organisms exhibit-

ing an eclosion delay of up to approximately 40% (Figure 2a).

This eclosion delay is accompanied by a decrease in larval size and

growth rate, and an increase in mortality at higher concentrations.

A decrease in reproductive success is observed in adults exposed

to uranium concentrations of 20 µg/l and higher. The impact on

fecundity (number of eggs laid – Figure 2b) is dramatic, with reduc-

tions of a factor of 2 and 60 for organisms exposed to uranium

concentrations of 20 and 250 µg/l, respectively. In addition, the

From test tubes to ecosystems

Ecotoxicology makes use of different complementary approaches,

ranging from monospecific laboratory biotests to field studies, as

well as laboratory experiments using more or less complex exper-

imental systems. Although in situ studies provide realism and inte-

gration of biological processes, their explanatory and predictive

potential for other situations remains limited due to the complex-

ity of the environment (space-time variables of ecological factors,

adaptation effects, etc.). Studies in controlled environments are

used to examine the responses of organisms to different exposure

conditions representative of potential situations (exposure levels

and pathways, duration, nature and chemical forms of the toxic

element considered, etc.). In a simplified approach, ecotoxicological

studies generally target organisms representative of the different

trophic levels. For example, in the case of continental aquatic

ecosystems, a distinction is made between planktonic species at

the base of the trophic network (algae, microcrustacean consumers),

benthic invertebrates associated with sediments, and fish.

The effects of environmental contaminants are first studied in the

laboratory by measuring responses at the individual level in terms

of fundamental biological processes. For example, in ecotoxicology,

life history traits are considered for all life stages of a given species:

eggs, larvae, juveniles, mature adults, etc. These life history traits

include reproductive capacity (fecundity, reproductive success, etc.)

and somatic growth. The data acquired concerning life history is

integrated into dynamic population models and used to establish

threshold values, i.e. doses or concentrations expected to have no

effect on all or part of an ecosystem. These values are necessary

for environmental risk characterization and management [Garnier-

Laplace et al, 2006 and 2008].

In addition, biological responses can be related to cellular or subcel-

lular alterations of certain specific tissues or organs. The magnitude

of these alterations is an indicator (i.e. biomarker) of exposure level

or effects of contaminants. Biomarkers are used extensively in

ecotoxicology due to their early response capability and their

sensitivity. They also provide a better understanding of toxic action

modes and cellular targets and improve identification of these

phenomena (Figure 1). In order to be useful in environmental risk

characterization, the biomarkers considered must be sensitive to

exposure to environmentally relevant doses, exhibiting quantifiable

dose-response relations and, if possible, reflecting the physiological

status of organisms or even populations.

Tissue/organ

Subcellular/cellular

Individual Population Community

Minutes Hours Days Months Years

Response time

Ecological relevance

Mechanistic basis

Figure 1 Main characteristics of effect indicators as a function of the level of biological organization studied.

Radioactivity in the environment 1. 1


Sensitivity of population dynamics to growth delay and energy budget (studies on Daphnia magna)

Based on data acquired at the individual level, mathematical mod-

els can be used to extrapolate the effects of contaminants on

populations.

This extrapolation is carried out using models of population dynam-

ics such as Leslie’s matrix model (Figure 3a). In this type of model,

the population structure is described as a distribution per age class.

viability of eggs and larvae decreases with the increase in uranium

concentration, since embryos are comparatively more exposed to

uranium through maternal transfer than through direct exposure

to the surrounding environment. These various criteria clearly

indicate the significant sensitivity of early life stages to uranium

exposure, either directly or through parental exposure, with sub-

lethal effects observed at concentrations of 20 µg/l and higher.

They also provide biological response data in terms of incidence on

populations. In a natural environment, the decrease in reproductive

success combined with the increase in larval mortality could have

a significant impact on the survival of certain populations.

Concentration (µg U /L)

HT50

(hpf)

055

60

65

70

75

80

85

90

20 50 100 150 250 500

Number of eggs laid per female

Cyprinid fish (24-hour embryo)Danio rerio

20 µg U/L 250 µg U/LControl group

600

500

400

300

200

100

0

**

Eggs(future cohort N1)

Cladocera microcrustaceanDaphnia magna

(juvenile)

Number of individuals

Time1 2 3…

i

i

Age

… Max. age

Survival index Si Fecundity index Fi

N1 = ∑ Fi • NiNi+1 = Si • Ni

Ni

Age i(at time t)

Age i +1(at t +1)

Decrease in fecundity

Reproduction time

Increase in mortality

% of effect on life history traits

0% 20% 40% 60% 80%0

2

3

1

Population growth period

Figure 2 Effect of uranium on Danio rerio. a) Mean eclosion time (HT50) expressed in hours of post-fertilization (hpf; average ± confidence interval of 95%; *: statistically different from control group, p < 0.05). b) Number of eggs laid by female after 20 days of exposure to uranium. Source: [Bourrachot et al, 2008a and 2008b].

Figure 3 a) Diagram of mathematical model of population structured by age (Leslie’s matrix model). b) Impact of responses of life history traits on the growth delay of Daphnia magna populations. Source: [Alonzo et al, 2008].

a

a

b

b

1. 1


energy of an organism cannot increase indefinitely, due to food

limitations in the environment and constraints specific to the spe-

cies. Every metabolic cost associated with pollution therefore occurs

at the expense of important processes for population dynamics.

Based on this approach, it is shown that uranium contamination at

concentrations of 25 µg/l and higher leads to critical perturbations

in the nutrition of Daphnia [Zeman et al, 2008]. Also, the slight

increase in energy expenditure (respiration) observed with

Americium-241 has a potentially significant impact on the mass

and survival of individuals in the offspring generation [Alonzo et al,

2006 and 2008].

Tolerance acquisition as an indication of microevolution (studies on Chironomus riparius)

Studies were conducted on the representative benthic invertebrate

Chironomus riparius to determine uranium toxicity at the individual

level for a first generation [Dias et al, 2008]. Subsequently, a com-

parison of the life history traits of populations initially identical but

exposed to different uranium concentrations for eight generations

(0, 32, 64 and 128 µg of uranium per gramme of dry sediment) led

to the identification of microevolutionary phenomena. Changes in

the phenotypic characteristics of populations contaminated for more

than two generations, as compared to control populations, may be

indicative of this type of microevolution [Bell and Collins, 2008]. For

example, as of the first generation, individuals exposed to uranium

exhibit a lower fitness (number of viable and fertile descendants, or

Changes in numbers of individuals in every age class over time are

determined by age-specific survival rates and fecundity rates.

Summing the fecundity of reproductive age-classes yields the num-

ber of individuals in the class of age 1. This simple model is used

to estimate the growth rate (in number of individuals) of a theo-

retical population (Figure 3b).

Due to its short parthenogenetic lifecycle, the zooplanktonic micro-

crustacean Daphnia magna is particularly suited for the acquisition

of data required in this type of model. In this approach, simulations

predicts a delay in population growth, i.e. an increase in the time

required for a population to grow from 10 to 106 individuals in

different conditions of exposure. It is also used to compare the

relative impact on population dynamics of changes in different

criteria measured at the individual level (survival rate, fecundity, age

at first reproduction). Working from the assumption that a popula-

tion is not limited in terms of food or space and that the effects

are the same from one generation to another, it can be shown that

the age at first reproduction has a dominant influence on population

dynamics of an organism such as daphnia (Figure 3b).

However, such models are limited to counting the number of

individuals in a population and does not make it possible to assess

impacts of contaminants on total biomass or biomass structure,

which are relevant ecological indicators. The ecological relevancy

of population dynamics can be improved by integrating physiolog-

ical aspects (food assimilation, energy expenditure, energy reserve,

production) into a dynamic energy budget model [Kooijman, 2000].

This approach is based on the assumption that the acquisition of

Generation

Mean fitness

Diptera insectChironomus riparius

(adult) - 40 1 2 3 4 5 6 7 8

-1

0

1

2

- 3

- 2

32 µg U/g 64 µg U/g 128 µg U/g0 µg U/g

Génération

Fitness moyenne

- 40 1 2 3 4 5 6 7 8

-1

0

1

2

- 3

- 2

32 µg U/g 64 µg U/g 128 µg U/g0 µg U/g

Figure 4 Evolution of mean fitness of Chironomus riparius in the course of eight generations, as a function of contamination (µg U/g of dry sediment). Source: [Dias et al, 2008].



Identification of subcellular biomarkers for a better understanding of the action mechanisms involved

Gene expression profiles

The biological responses observed from the individual level to that

of populations are often the result of various distinct kinetic toxic-

ity mechanisms taking place at the subcellular level and specific to

each target organ. The analysis of gene expression profiles in dif-

ferent organs can constitute a powerful approach to understanding

the diversity of the toxicity mechanisms underlying the effects

observed at other levels of biological organization. This approach

has been used on zebrafish in order to identify the toxic action

mechanisms of uranium in four target organs: gills, skeletal tissue,

liver and brain.

The expression level of a set of 20 genes involved in cellular toxic-

ity mechanisms (Table 1) has been measured by RT-PCR (Reverse

Transcription-Polymerase Chain Reaction) in male zebrafish exposed

to approximately 20 and 100 µg of depleted uranium per liter. The

gene expression profiles show that at concentrations of 20 µg/l and

higher, uranium exposure induces a change in the expression of

certain genes involved in inflammatory and oxidative response.

Genes involved in apoptosis (particularly in skeletal tissue), mito-

chondrial metabolism and DNA repair are also affected. In the brain,

the vchat and gls1 genes are also induced, which indicates a neural

response affecting glutamate synthesis and the cholinergic system,

consistent with the previously reported effects of uranium on

variations in acetylcholinesterase activity [Barillet et al, 2007).

Genetic responses vary depending on the organ considered. In the

gills, despite the accumulation of high concentrations of uranium,

product of survival and fecundity rates) than non-exposed individu-

als (Figure 4). However, this decrease in fitness disappears gradually

from one generation to the next for all uranium concentrations, and

by the eighth generation exposed individuals exhibit the same size

as non-exposed individuals. Is this a genetic selection in response to

uranium exposure? To answer this question, "common garden"

experiments were conducted [Falconer and Mackay, 1996], consisting

of transferring all test populations to the same non-contaminated

environment and comparing their performance data. The results

obtained have revealed a phenotypic divergence suggesting a genet-

ic divergence between the control populations and those previously

exposed to uranium. However, other measurements taken in the

course of this experiment seem to show that, despite the adaptation

of exposed populations to uranium, the metabolic cost of acquiring

this tolerance makes them more vulnerable to a new environment,

even if it is identical to their original environment.

When populations previously exposed to significant uranium con-

tamination (128 µg of uranium per gramme of dry sediment) are

placed once again in a non-contaminated environment, they exhib-

it a lower reproductive success rate than the control populations.

This result suggests that rapid and frequent environmental changes,

as compared to the characteristic duration of a generation (or life-

cycle), may have an environmental impact on populations specialized

for a specific environment, and that these populations could tend to

disappear. Although these populations are clearly capable of adapt-

ing to an environment contaminated with uranium, the metabolic

cost of this tolerance acquisition can make them more vulnerable to

a new environment (e.g. lower reproductive success rate than control

populations). This example illustrates the complexity of the eco-

logical processes involved and the multitude of indirect effects to be

considered.

Table 1 Comparison of gene expression alterations in four target organs of uranium for zebrafish exposed to 20 or 100 µg/l [Lerebours et al, 2008].

Cellular processes Brain Skeletal tissue Liver Gills

Detoxification cytp450 tap, cytp450 tap, cytp450 –

Stress oxydantgpx, gst, cat

catgpx, gst, cat, sod(Cu/Zn),

sod(Mn)gpx, sod(Mn)

Apoptose – bax bax –

DNA repair gadd – gadd rad51(1)

Mitochondrial metabolism – coxI coxI coxl(1)

Inflammation il1 il1 il1 –

Neural response vchat, cd11b, gls1 Undetermined Undetermined Undetermined

(1) Alteration observed only at 100 µg U/l.

1. 1


Certain types of damage may be correctly repaired with normal

pursuit of the cell cycle, other types may be non-repairable,

resulting in the elimination of cells affected by apoptosis, and

others may be incorrectly repaired. In the latter case, irreversible

effects may occur, such as mutations, carcinogenesis and terato-

genesis.

In vitro studies

Fish primary cell cultures for in vitro studies have been developed

to establish rapid and sensitive tests for discerning the genotoxic

potential of uranium and thereby identify the most sensitive in vivo

exposure scenarios. The alkaline comet test has been privileged for

the detection of genotoxic events. This test detects single and

double-stranded DNA breaks, as well as alkali-labile sites. It requires

the dissociation of tissues in order to isolate cells without altering

their DNA.

Among the various possible cell types, germ cells and hepatic cells

have been selected, since they are particularly useful in evaluating

genotoxicity. An alteration of the genetic material of gametes can

compromise an organism’s ability to produce viable descendants,

and can modify the genetic constitution of subsequent generations

by introducing more or less deleterious mutations, thereby causing

a severe impact on population dynamics. The liver plays a central

role in the general metabolism of an organism, and also in the

detoxification and transformation of toxic molecules penetrating

the organism.

a very limited number of genes is induced at the higher concentra-

tion level, and very moderately so (maximum induction factor

of 7), suggesting a low sensitivity of this organ to uranium exposure.

In the liver, where high concentrations of uranium also accumulate,

genetic responses (induction or repression) are observed for a large

number of genes (maximum repression factor of 100), mainly at

the lower exposure concentration (20 µg/l). The absence or decrease

in number of repressed or overexpressed genes during exposure to

a high concentration of uranium could indicate that the organ’s

defense capacity has been exceeded, which can be corroborated

with the liver histopathologies observed by other researchers [Cooley

et al, 2000]. Finally, in the brain and skeletal tissue, where the

accumulation of uranium is approximately 10 times lower, numer-

ous genes respond precociously and with a more marked intensity

at the lower concentration level, clearly indicating the sensitivity

of these organs to uranium exposure, in conjunction with the

potential neurological effects of this element.

DNA alterations and effects at the individual level

Exposure to radionuclides can directly modify the structure and

function of the main biological macromolecules: lipids, sugars,

proteins, and nucleic acids. It is generally acknowledged that DNA

is the target molecule of radiation-induced damage and associ-

ated biological effects. The impact of the various structural DNA

modifications induced by ionizing radiation can be more or less

severe, depending on how they are repaired by cellular defense

mechanisms.

00 1 10 100 750

10

20

30

40

DNA in comet tail (%)


Depleted uranium (µM)Dose rate (mGy/day)

00 1 10 100

10

20

40

50

30

* *

**

**

** ***

Hepatocytes Gametes Hepatocytes Gametes

DNA labelled with ethidium bromideBottom: intact DNATop: damaged DNA

Figure 5 Level of DNA damage (percentage of DNA in comet tail) in male gametes and hepatocytes exposed for 24 hours to (a) dose rates (external gamma radiation, 137Cs) and (b) concentrations of depleted uranium. Average ± standard error (n = 5; *: p < 0.05, **: p < 0.01, ***: p < 0.001). [Giraudo, 2006].

a b



adults were directly exposed for 20 days to depleted uranium in

concentrations of 20 and 250 µg/l [Bourrachot et al, 2008b]. In

the case of individuals exposed to a uranium concentration of

250 µg/l, a decrease in reproductive performance was observed

(Figure 2b), associated with a significant increase in the quantity

of DNA damage in male and female germ cells (Figure 6). The

uranium concentrations in tissue (5 to 15 mg of uranium per kg

of gonad, calculated based on a fresh-to-dry-weight ratio of five)

are of the same order of magnitude as the concentrations used in

vitro (2.4 to 24 mg/l in the culture environment), which confirms

that cell cultures may be used as a screening tool.

This consistency between the data obtained from in vitro and in

vivo studies, combined with the identification of target organs of

uranium accumulation exhibiting high cell sensitivity, implies that

the effects observed at the molecular level may be linked to those

observed at the individual level. Nevertheless, this type of correlation

does not necessarily imply a direct cause and effect relationship,

and may merely indicate common toxic action mechanisms.

Conclusion

The approach adopted with uranium to identify individual

responses and their impact on populations, in conjunction with

action mechanisms identified at the subcellular level, shows how

current knowledge of the ecological consequences of chronic

exposure to low concentrations of radionuclides could be gradu-

ally improved, and which tools could be used in the future for

determining the ecological status of a contaminated ecosystem.

This approach is particularly useful for developing a relevant

ecological risk assessment method, particularly through the use

of scientifically founded extrapolation tools (e.g. extrapolation of

effects from individuals to populations using mathematical mod-

els). These developments require further experimental studies to

select ecologically relevant criteria and gradually replace current

extrapolation rules with adequate knowledge.

Effect biomarkers can also be used to further knowledge on the

predominant accumulation and effect targets in organisms (in

conjunction with the Human Health part of the ENVIRHOM

research program) by using tools based on the observation of

early response, useful for monitoring ecosystem contamination.

The sensitivity of the two cell types considered (hepatocytes and

male gametes) has been compared for exposure to external gamma

radiation or depleted uranium (Figure 5). In the case of exposure

to external gamma radiation, a significant increase in the number

of DNA breaks is observed in gametes at 1 mGy/day, whereas

hepatic DNA alterations only occur at 750 mGy/day. Likewise, in

the case of exposure to depleted uranium, a significant increase in

DNA damage is observed in male gametes at the second uranium

concentration level (2.4 mg/l), whereas no significant trend is

observed in hepatocytes. These results show that the extent of DNA

damage is a function of the cell type considered, characterized by

the repair capacity of the DNA and a specific cellular renewal rate.

Since spermatozoa lack efficient DNA repair systems, they maintain

DNA integrity with difficulty and are therefore more sensitive to

the presence of genotoxic agents in the environment than hepa-

tocytes.

In vivo studies

The high sensitivity of germ cells observed in vitro leads to the

consideration of possible effects on reproductive parameters. An

in vivo study was therefore conducted to determine the link between

DNA alterations in germs cells and effects on fecundity. Danio rerio


Spermatozoa (light microscope)

250 µg U/L20 µg U/L0

Control

5

10

20

25

30

35

40

15*

***

Female gametes Male gametes

x 200

Figure 6 DNA damage measured by comet tests on male and female gonad cells. Average ± standard deviation (n = 3; *: p < 0.05 and ***: p < 0.001). Source: [Bourrachot et al, 2008].

1. 1


References

F. Alonzo, R. Gilbin, S. Bourrachot, M. Floriani, M. Morello, J. Garnier-Laplace (2006). Effects of chronic internal alpha irradiation on physiology, growth and reproductive success of Daphnia magna. Aquat Toxicol 80(3), 228-236.

F. Alonzo, T. Hertel-Aas, M. Gilek, R. Gilbin, D.H. Oughton, J. Garnier-Laplace (2008). Modelling the propagation of effects of chronic exposure to ionising radiation from individuals to populations. J Environ Radioactiv, 99, 1464-1473.

S. Barillet, C. Adam, O. Palluel, A. Devaux (2007). Bioaccumulation, oxidative stress and neurotoxicity in Danio rerio exposed to different isotopic compositions of uranium. Environ Toxicol Chem 26(3), 497-505.

G. Bell, S. Collins (2008). Adaptation, extinction and global change. Evol Appl 1, 3-16.

S. Bourrachot, O. Simon, R. Gilbin (2008a). The effects of waterborne uranium on the hatching success, development and survival of early life stages of zebrafish (Danio rerio). Aquat Toxicol, publication in progress.

S. Bourrachot, L. Aubergat, O. Simon, R. Gilbin (2008b). Effects of uranium on reproduction of zebrafish: relationships between biomarkers of exposure and toxicity. Congrès SETAC Europe, Varsovie, 25-29 mai.

H.M. Cooley, R.E Evans, J.F. Klaverkamp (2000). Toxicology of dietary uranium in lake whitefish (Coregonus clupeaformis). Aquat Tox 48, 495-515.

V. Dias, C. Vasseur, J.M. Bonzom (2008). Exposure of Chironomus riparius larvae to uranium: effects on survival, development time, growth, and mouthpart deformities. Chemosphere 71(3), 574-581.

European Commission (2003). Technical Guidance Document. Dir. 93/67/EEC and Reg. EC 1488/94, Dir. 98/8/EC.

D.S. Falconer. T.F.C. Mackay (1996). Introduction to Quantitative Genetics, Ed 4. Longmans Green, Harlow, Essex, UK.

J. Garnier-Laplace , C. Della-Vedova, R. Gilbin, D. Copplestone, J. Hingston, P. Ciffroy (2006). First derivation of predicted-no-effect values for freshwater and terrestrial ecosystems exposed to radioactive substances. Environ Sci Technol 40, 6498-6505.

J. Garnier-Laplace, D. Copplestone, R. Gilbin, F. Alonzo, P. Ciffroy, M. Gilek, A. Agüero, M. Björk, D.H. Oughton, A. Jaworska, C.M. Larsson, J.L. Hingston (2008). Issues and practices in the use of effects data from FREDERICA in the ERICA Integrated Approach. J Environ Radioactiv, 99, 1474-1483.

M. Giraudo (2006). Développement et optimisation du test des comètes sur cellules primaires isolées de poisson zèbre (Danio rerio) : application à l’étude des effets de l’uranium. Stage de Master II, Master Recherche bioinformatique, biochimie structurale et génomique, université de Provence – Aix-Marseille I.

S.A.L.M. Kooijman (2000). Dynamic energy and mass budgets in biological systems. University Press, Cambridge, 424 p.

A. Lerebours, P. Gonzales, C. Adam, V. Camilleri, J.-P. Bourdineaud, C. Garnier-Laplace (2008). Comparative analysis of gene expression in brain, liver, skeletal muscles and gills of the zebrafish (Danio rerio) exposed to environmentally relevant waterborne uranium concentrations. Submitted to Environ Toxicol Chem.

F.A. Zeman, R. Gilbin, F. Alonzo, C. Lecomte-Pradines, J. Garnier-Laplace, C. Aliaume (2008). Effects of waterborne uranium on survival, growth, reproduction and physiological processes of the freshwater cladoceran Daphnia magna. Aquat Toxicol 86(3), 370-378.

1.2

newsflashnewsflashnewsflashnewsflashnewsflashnewsflash


Rodolphe GILBIN, Catherine LECOMTE-PRADINES,

Céline RÉTY, Florence ZEMANRadioecology and Ecotoxicology Laboratory

(1) Technical Guidance Document on Risk Assessment – http://ecb.jrc.it/Technical-Guidance-Document/

(2) ERICA integrated assessment tool – http://www.erica-project.org/

In the event of chronic exposure of a con-

tinental aquatic ecosystem to low concentra-

tions of contaminants, risk assessments

currently performed often result in the iden-

tification of several potentially hazardous

contaminants (chemical or radioactive sub-

stances). These contaminants may act in a

synergic or antagonistic manner, and their

effects add up with those of natural variables

(temperature, luminosity, eutrophication,

etc.). Ecological risk assessments need to take

these interactions into account, whether to

determine the exposure of living organisms

or to assess potential effects. However, the

operational assessment methods currently

recommended by the European Agency for

Chemical Substances (described in the

Technical Guidance Document on Risk

Assessment(1)) and the tools recently pro-

posed for assessing the ecological risks asso-

ciated with radionuclides(2) do not provide

relevant models of multistress contexts, since

mixture scenarios are not considered.

The project considered here is being

conducted in the Radioecology and

Ecotoxicology Laboratory in conjunction

with the Environmental part of the

ENVIRHOM research program. It began in

2005 with a first study on daphnia, an

aquatic microcrustacean (thesis defended

by F. Zeman in October 2008). This study

has led to the establishment of a method-

ological framework for the identification

of interactions in a binary mixture of ura-

nium and selenium.

The general approach is illustrated in

Figure 1:

exposure studies are performed by evalu-

ating the potential physical and chemical

interactions between contaminants and

their impact in terms of exposure of bio-

logical ecosystem components (exposure

of habitats, bioavailability);

effect studies are conducted by establish-

ing dose-effect relationships to determine

the effect levels for each substance consid-

ered individually, and by applying modeling

methods for mixture effects (i.e. concentra-

tion addition; independent action);

risk characterization studies are con-

ducted by integrating interactions at the

exposure and effect level.

The results obtained have shown that a

complete test design (i.e. testing each

binary mixture in variable proportions) is

indispensable for identifying a genuine

interaction between the different sub-

stances. As a result, an antagonistic effect

of selenium on uranium toxicity was iden-

tified. Further research is being conducted

within the framework of a joint project

between IRSN and EDF (GGP-Environment

project) devoted to improving prospective

TAkiNG iNTo ACCouNT iNTERACTioNS between radioactive substances and chemical substances to improve ecological risk assessment in a multipollution context

newsflashnewsflashnewsflashnewsflashnewsflashnewsflash


or retrospective assessments of potential

risks for continental aquatic ecosystems

(large rivers), associated with chronic, spo-

radic, or diffuse release from nuclear power

plants (NPP) under normal or incident oper-

ating conditions, taking into account the

specific characteristics of their catchment

basins. This research considers a number of

chemical substances (metals, organic

micropollutants) and radioactive substanc-

es (beta and gamma radiation emitters),

particularly as a function of natural stress

parameters (eutrophication, temperature).

Experimental studies (thesis by C. Réty,

2007-2009) have been devoted to a lim-

ited number of substances representative

of routine releases from NPP and charac-

teristic of specific exposure types (e.g. cop-

per, tritium), and to a phytoplanktonic

organism (growth inhibition in a monocel-

lular green alga, photosynthesis and oxida-

tion stress). The effect of gamma radiation

has also been studied on this organism.

As a supplement to the research con-

ducted within the framework of the

ECOSENSOR program, coordinated by the

National Institute of Universe Sciences

(CNRS-INSU) in collaboration with the

Hydrosciences Laboratory of the University

of Montpellier and the Macromolecular

Biochemistry Research Center (CNRS UMR

5237, Montpellier), the project considered

here aims to study the effects of mixtures

of contaminants with different action

mechanisms (cadmium, nonylphenol,

gamma radiation emitters) using wild-type

and mutant nematode C elegans as biosen-

sors.

The final objective is to provide an eco-

logical risk indicator based on comparison

with environmental monitoring data, so as

to validate new interaction models and

define their scope of application.

Total concentration

Bioavailable concentration

Internal concentration

Toxic effect

Speciation

Total concentration

Bioavailable concentration

Speciation

Substance 1 Toxico-kinetic

Substance 2

EXPOSURE

Internal concentration

Toxic effect

Toxico-kinetic

Toxico-dynamic

Toxico-dynamic

Interaction Interaction Interaction ? ? ?

Figure 1 Schematic representation of the different possible levels of interaction between two substances (thesis by F. Zeman, 2008).


From 2005 to 2007, IRSN teams participated in the SaliFa-

PRIMEQUAL research program(1) [Sacré et al, 2006], whose general

objective was to acquire a better understanding of the physical

mechanisms responsible for the soiling of building façades. Various

teams collaborated on this project. The National Center for Building

Science and Technology (CSTB), the Interprofessional Research

Center for Aerothermochemistry (Coria) and the Central Research

Institute in Nantes (ECN) participated in building analysis, micro-

meteorological measurement and digital simulation activities.

The dry deposition study consisted of short-term and long-term

experiments conducted by IRSN in the city of Nantes.

The short-term experiments were used to study dry deposition

processes as a function of different parameters such as substrate

temperature or atmospheric turbulence. Calibrated fluorescein

aerosols were artificially generated to quantify dry deposition.

The long-term experiments consisted of conducting a global anal-

ysis of deposition phenomena using beryllium-7 (7Be) as a tracer

of dry deposition. This radionuclide is naturally present in the air

as an aerosol.

Test specimens were selected by CSTB and consisted of two types

of glass (non-treated glass and titanium oxide-coated glass requir-

ing reduced maintenance and less frequent cleaning) and three

types of façade coatings with a surface roughness of 2, 3 and

5 mm.

The different teams involved in the project participated at different

stages. The CSTB team selected and prepared the glass and coating

Denis MARO, Olivier CONNAN, Didier HÉBERT, Marianne ROZETRadioecology Laboratory of Cherbourg-Octeville

Urban areas contain over 70% of the population in most developed countries. The potential radiological impact

of contamination in urban environments is therefore an issue of current interest for the management of post-

accident situations. In order to consider the hypothetical case of an accident or act of terrorism involving

radionuclides in gaseous or aerosol form in an urban environment, it is important to have a good understanding

of radionuclide transfer processes throughout the urban ecosystem so as to predict their impact on populations.

For several years now, IRSN teams have been studying the dry deposition of aerosols on the surfaces of build-

ings. To date, the dry deposition of aerosols remains a research area seldom explored at the international level.

This research requires an in situ experimental approach to take into account specific local characteristics (turbu-

lence, substrates, etc.) [Maro et al, 2004].

THE SAlIFA PRIMEQuAl PROjECT: A study on dry deposition of aerosols in an urban environment

1. 3

(1) Inter-organism research program for better local air quality, coordinated by the French Ministry for Ecology and Sustainable Development and the French Agency for Environmental and Energy Management (Ademe).


1. 3

integrated over the entire plume passage time at the observation

time, and the total quantity of SF6 emitted. SF

6 was more appropri-

ate for spot measurements than fluorescein, when it was necessary

to compensate for the lack of systematic measurements of fluo-

rescein concentration in the air (only two measurements per

experiment) and to check substrate concentration homogeneity

(Figure 2).

Micrometeorological measurements were also performed at the

test site, near the aerosol generation system and near the sub-

strates.

This method (Figure 1) was applied during two field test campaigns.

The SaliFa 1 and 2 campaigns were conducted from June 28 to 30,

2005, in downtown Nantes (Medical school conference center), and

from June 6 to 8, 2006, at ECN (Figures 3 and 4).

Emission of fluorescein aerosols and SF6 tracer gas

Aerosols were emitted in the air using a pneumatic fluorescein

generator. The various modules for air spraying, dilution and drying

were adjusted to generate particles with a mean mass diameter of

0.2 µm (dry aerosol). This mean mass diameter was chosen because

it corresponds to that of the accumulation mode of particles in an

urban environment [Boulaud and Renoux, 1998].

The system was calibrated [AFNOR NFX 44-011, 1972] to obtain

particles with a mean mass diameter of 0.24 µm (standard geometric

deviation of 1.7). Fluorescein aerosols were generated for a period

of 60 minutes and the distance between the fluorescein emission

point and the various substrates placed in the emission stream was

15 m.

specimens tested and ensured on-site management of the long-term

experimental campaign (Nantes medical school conference center),

the ECN team performed meteorological measurements and

numerical simulations, the Coria team performed turbulent flux

measurements near substrate walls, and the IRSN team measured

the dry deposition rates of aerosols during the short-term and

long-term experimental campaigns.

Experimental equipment and methods

Short-term experimental campaigns: measuring aerosol

dry deposition rates using a dry deposition tracer

Principle

The method developed by the Radioecology Laboratory of Cherbourg-

Octeville (LRC) can be used to determine the dry deposition rates

of aerosols by emitting fluorescein (uranin) in dry aerosol form

toward an experimental setup comprising atmospheric aerosol

sampling systems and the various substrates studied (Figure 1).

After emission, samples were collected for subsequent measurement

by spectrofluorometry.

The deposition rate (m.s-1) was calculated as the ratio between the

dry deposition flux on the substrate (kg.m-2.s-1) and the atmo-

spheric concentration at the substrate level (kg.m-3).

A tracer gas (sulfur hexafluoride, SF6) was emitted simultaneously

with the fluorescein so as to determine the atmospheric transfer

coefficient (ATC, i.e. time-integrated concentration at a given point,

normalized to the total quantity released) and thereby obtain the

atmospheric aerosol concentration at the level of each substrate.

The ATC was calculated as the ratio between the SF6 concentration

Emission (fluorescein aerosols)0.2 µm - 60 min

Emission point

Emission (SF6 tracer)

Wind direction

Distance – 15 m

Substrates

Sampling on filters

(HVS)

Air

Meteorology, micrometeorology and granulometry

of atmospheric aerosols

SF6 concentration measurements on five types of substrate

Recovery

Fluorescein extraction

Fluorescein measurements (air and substrate)

Dry deposition rate(ratio between dry deposition

flux and atmospheric concentration)

Figure 1 Diagram of experimental setup.

Radioactivity in the environment


1. 3

modules to collect atmospheric aerosol samples. After each emis-

sion, the various test samples (air filters and test tubes) were

protected with aluminum foil and stored for subsequent analysis.

Air samples for SF6 analysis were taken in 1-liter gas bags (TedlarR)

throughout the duration of fluorescein emission, using a specific

technique developed by IRSN (DIAPEG). Samples were taken at the

four corners and at the center of the test tube holder (Figure 2).

Measurement of concentration of fluorescein aerosols and

SF6 tracer gas

To measure the concentration of fluorescein aerosols in the air, the

filters were switched off and immersed in an aqueous ammonia

solution at pH 9, with mechanical agitation for 20 minutes. To

measure the concentration of aerosols deposited on the substrates,

SF6 was emitted as a tracer gas simultaneously with the fluores-

cein aerosols (30 mg.h-1). This gas is not naturally present in the

atmosphere. The system used consists of an SF6 canister (Messer)

connected to a mass flow meter (Sierra 820). The gas was emitted

through the aerosol spray tube (SF6 emission rate = 0.4 g.s-1).

Sampling of fluorescein aerosols and SF6 tracer gas

Fluorescein aerosols were sampled from the emission stream in

order to measure the concentration in the air and on the glass and

façade coating substrates. Atmospheric aerosols were collected on

Whatman 40 filters (Ashless 40-1440917) via two high volume

samplers (HVS) with a flow rate of 30 m3.h-1.

During fluorescein emission, three test tubes of each type were

placed on a holder in the fluorescein plume flow near the HVS

Vertical façade

HVS(aerosol sampling)

HVS(aerosol sampling)

Coating (3 mm) Coating (5 mm)Non-treated

glass

Low-maintenance

glassCoating (2 mm)


glass

Low-maintenance

glassCoating (2 mm)


glass

Low-maintenance

glassCoating (2 mm)

DIAPEG 1(air sampling)





Figure 2 Basic diagram of position of substrates, aerosol sampling systems (HVS) and air sampling systems (DIAPEG).

Figure 3 Short-term experimental campaign: position of substrates and sampling systems (Nantes medical conference center).

Figure 4 Short-term experimental campaign: position of substrates and sampling systems (ECN).

HVS

Test specimens (glass, coatings)

Meteorological station

Release (fluorescein, SF

6)

DiAPEG

HVSTest specimens (glass, coatings)

ultrasonic anemometers

Release (fluorescein, SF

6)

DiAPEG


spectrometry in a laboratory with low background noise (French

navy underground laboratory, EAMEA/GEA). The 7Be activity depos-

ited on each specimen was measured and compared with the mean

atmospheric activity of 7Be at the moment of exposure, so as to

determine the deposition rate. The 7Be activity in the atmosphere

was not measured in Nantes. Values measured by the Metrology

Library (IRSN Orsay) in different sites such as Alençon and Bordeaux

were used.

Results and discussion

Short-term campaigns

Measurements were performed under low wind conditions, i.e.

1 to 2.2 m.s-1. Air friction against the soil (U*) ranged from 0.1 to

0.6 m.s-1. The deposition rates obtained during the experimental

campaigns in June 2005 (SaliFa 1) and June 2006 (SaliFa 2) are

summarized in Table 1. Dry deposition rates ranged from 1.1.10-5

to 3.0.10-5 m.s-1 for glass specimens and from 4.2.10-5 to 1.2.10-4

m.s-1 for façade coating specimens.

The dry deposition rates obtained during the SaliFa 1 and 2 test

campaigns were, respectively, 3.0.10-5 m.s-1 and 1.5.10-5 m.s-1 for

non-treated glass, and 2.8 .10-5 and 1.1.10-5 m.s-1 for low-mainte-

nance glass. Taking into account the associated uncertainties

(< 58%), no significant differences were observed between the

two types of glass. The deposition rates were systematically

higher for both types of glass during the SaliFa 1 campaign. The

higher air temperatures and insolation values during the SaliFa 2

campaign could have had an influence, via the thermophoresis

effect.

During the SaliFa 2 campaign, the air temperature and the surface

temperatures of the different specimens were measured to take

this influence into account. In the case of glass, the deposition rates

the glass specimens and façade coating specimens were washed

with an ammonia solution at pH 9. The washing solutions were

then filtered at 0.2 µm prior to measurement by spectrofluorometry.

Fluorescein concentration measurements were performed using a

UV spectrofluorometer (Horiba Fluoromax-3). The excitation wave-

length was set to 490 nm and emission was measured at

512 nm.

The SF6 content in the air samples was measured by gas phase

chromatography (AUTOTRAC, Lagus Applied Technology Inc.).

Acquisition of micrometeorological data

Micrometeorological data (particularly air friction against wall and

soil) was obtained using ultrasonic anemometers (Young 81000,

20 Hz) placed at different points throughout the test site. In addi-

tion to this setup, a meteorological station (PULSONIC) was placed

between the fluorescein generator and the test tube holder to

measure wind speed and direction, relative humidity, temperature

and atmospheric pressure. Substrate wall temperature was also

measured during the SaliFa 2 campaign, using an FX 410 infrared

thermometer (Jules Richard Instruments).

Long-term experimental campaign: use of 7Be naturally

present in the atmosphere as a dry deposition tracer

In addition to the short-term experimental campaigns, a long-term

campaign was conducted to determine the soiling impact of aero-

sol deposition and to quantify the dry deposition. The same types

of urban substrates as those used during the short-term campaigns

were installed on a wall in downtown Nantes from April 2005 to

August 2006 (Figure 5). These substrates were placed on the north-

east façade of the Medical school conference center, therefore

protected from heavy rain. Samples were taken periodically after

different periods of exposure to urban pollution and at different

times of the year.

The method implemented consisted of measuring the 7Be deposi-

tion on the glass specimens and façade coating specimens. 7Be is

a radionuclide with a half-life of 53.2 days, naturally present in the

atmosphere, which adheres to atmospheric aerosols with a particle

size in the order of 0.4 µm. 7Be activity levels in the atmosphere

depend on air mass exchanges between the troposphere and strato-

sphere, and on the dry and wet deposition of aerosols. This radio-

nuclide can therefore be used as a tracer of deposition. Once they

were removed from the exposure wall, specimens were treated as

quickly as possible, since the half-life of 7Be is quite short. The

specimens removed from the wall were rinsed with acidified water.

The radioactivity of the wash water was then measured by gamma

1. 3

Figure 5 Long-term experimental campaign: position of substrates on the northeast façade of the Nantes medical conference center.



similar differences in the deposition rates of coating specimens and

glass specimens.

At this stage, it is difficult to explain these differences, but air

temperatures and substrate surface temperatures probably play a

role. Unfortunately, the temperature of the substrate walls was not

measured during the SaliFa 1 campaign. The results obtained during

the SaliFa 2 campaign indicated that this was a significant param-

eter. In the case of micrometeorological parameters such as rough-

ness length and wall and soil friction, the differences between the

two campaigns appeared to be minimal, and the micrometeoro-

logical conditions during the two campaigns can be considered as

similar. No relationship was demonstrated between variations in

deposition rate and with these micrometeorological parameters.

Long-term campaign

Three series of measurements were performed, corresponding to

test specimens removed from the exposure wall in December 2005

(after 8 months of exposure time), April 2006 (after 12 months of

were inversely proportional to the surface temperature of the

specimens (Figure 6), and they decreased as the temperature dif-

ference between the air and substrate wall increased (Figure 7).

The average dry deposition rates obtained for the different façade

coatings are listed in Table 1. They range between 4.2.10-5 and

1.2 10-4 m.s-1, with no significant differences between coatings with

different roughness values. The temperature difference between

the air and the coating specimens was much lower than for the

glass specimens (3°K and 8°K, respectively). As a result, no correla-

tion was observed with the deposition rate. As in the case of the

glass specimens, the deposition rates obtained during the SaliFa 1

campaign were slightly higher (by a factor of approximately 2).

It should also be noted that the difference between the deposition

rates for glass specimens and coating specimens was similar during

each campaign. The deposition rates for coating specimens were

higher than those for glass specimens by a factor of 3.8 during the

SaliFa 1 campaign and by a factor of 3.5 during the SaliFa 2 campaign.

The results for both campaigns were therefore consistent, showing

1. 3

Emission number

00 1 2 3 4 5 6

Deposition rate (m.s-1) 1/T° glass (K-1)

2.5.10-5

2.10.10-5

1.5.10-5

1.10.10-5

5.10-6

Low-maintenance glass

Inverse of substrate temperature

Non-treated glass

3.5.10-3

3.4.10-3

3.3.10-3

3.2.10-3

Deposition rate (m.s-1)

T° glass - T° air (°K)1 2 3 4 5 6 7 8 9

Low-maintenance glass

Non-treated glass

2.5.10-5

2.10-5

1.5.10-5

1.10-5

5.10-6

0

Figure 6 Variations in dry deposition rate and inverse of glass temperature (1/T, in °K-1) for different emissions during the SaliFa 2 campaign.

Figure 7 Variations in the deposition rate as a function of the deviation between air and glass temperature (°K).

Campaign Non-treated glassLow-maintenance

glass

Coating with roughness value of 2 mm



SaliFa 1 3.0.10-5 2.8.10-5 1.2.10-4 9.6.10-5 1.2.10-4

SaliFa 2 1.5.10-5 1.1.10-5 5.1.10-5 4.2.10-5 4.5.10-5

Average values 2.2.10-5 1.9.10-5 8.5.10-5 6.9.10-5 8.2.10-5

Table 1 Average dry deposition rates of aerosols (m.s-1) determined for different substrates during the SaliFa 1 and 2 short-term campaigns in June 2005 and June 2006 (maximum uncertainty 58%).


concerning the assessment of deposition rates on urban substrates.

Nevertheless, the studies conducted by Roed (1983, 1985, 1986,

1987) allow for a comparison of certain data. In particular, Roed

determined the dry deposition rates of aerosols on different urban

substrates based on the cesium-137 (137Cs) released to the atmo-

sphere during nuclear atmospheric tests prior to the Chernobyl

accident, and based on the various radionuclides released further

to the accident. He also used the 7Be naturally present in the

atmosphere as a dry deposition tracer.

In the studies conducted prior to the Chernobyl accident [Roed,

1983, 1985], the author indicated that the particle size distribution

of 137Cs obtained from the atmospheric tests was not perfectly

accurate, but probably close to that of 7Be, which had a mean

aerodynamic diameter of 0.4 µm. The deposition rate values obtained

were very low. For vertical surfaces, the deposition rates determined

from 137Cs measurements were less than 1.10-4 m.s-1. The values

obtained for 7Be were approximately 1.6.10-4 m.s-1, i.e. very close

to those obtained for 137Cs.

In the studies conducted after the Chernobyl accident (Table 4),

[Roed, 1986, 1987], the author determined the dry deposition rates

for iodine-131 (131I), cesium-137 (137Cs), ruthenium-103 (103Ru),

barium-140 (140Ba), cerium-144 (144Ce) and zirconium-95 (95Zr).

Roed listed the following mean aerodynamic diameter values: 0.4 µm

exposure time) and August 2006 (after 8 months of exposure time).

The exposure time was therefore variable, but given the half-life

of 7Be (53.2 days), the average exposure time of the specimens was

considered to be two months.

The results obtained are listed in Table 2. Dry deposition rates

ranged from 3.2.10-5 to 3.9.10-5 m.s-1 for non-treated glass and from

1.4.10-5 to 3.4.10-5 m.s-1 for low-maintenance glass. For façade

coatings, dry deposition rates ranged from 1.1.10-4 to 3.4.10-4 m.s-1.

In all cases, the uncertainty associated with the deposition rate was

less than 54%.

The deposition rates for glass specimens were systematically lower

than for coating specimens, which is consistent with the results

obtained during the short-term experimental campaigns. As in the

case of the short-term campaigns, no significant variations were

observed between different glass types, or between different coating

types.

In addition, the dry deposition rates measured during the short-term

and long-term campaigns were of the same order of magnitude

(Table 3), with a deviation less than a factor of three.

Comparison with results in the "literature"

The international "literature" contains little experimental data

1. 3

Exposure time

Non-treated glass

Low-maintenance

glass




April 2005 – December 2005 3.9.10

-5 3.4.10-5 2.3.10-4 1.5.10-4 1.1.10-4

April 2005 – April 2006 – * – * 2.8.10-4 2.6.10-4 3.4.10-4

December 2005 – April 2006

3.2.10-5 1.4.10-5 2.1.10-4 1.7.10-4 1.7.10-4

Average values 3.5.10-5 2.4.10-5 2.4.10-4 1.9.10-4 2.1.10-4

Table 2 Average dry deposition rates of aerosols (m.s-1) determined for different substrates during the long-term exposure campaign (*: non-significant measurements, maximum uncertainty 54%).

Campaign Non-treated glass

Low- maintenance

glass




Short-term 2.2.10-5 1.9.10-5 8.5.10-5 6.9.10-5 8.2.10-5

Long-term 3.5.10-5 2.4.10-5 2.4.10-5 1.9.10-4 2.1.10-4

Long-term to short-term ratio

1.6 1.3 2.8 2.7 2.6

Table 3 Comparison of dry deposition rates of aerosols (m.s) determined during the long-term and short-term experimental campaign.



the different studies, the results obtained have been considered as

consistent.

Conclusion

As part of the SaliFa-PRIMEQUAL research program, several

field test campaigns were conducted to measure the dry depo-

sition rates of aerosols in an urban environment by means of

glass specimens and façade coating specimens.

These deposition rates were obtained using two complemen-

tary methods. The first method consisted of using a tracer of

the deposition of fluorescein aerosols artificially generated

during two short-term experimental campaigns (SaliFa 1 and

2). The second method consisted of using 7Be, a radionuclide

naturally present in the atmosphere in aerosol form, as a tracer

of the deposition generated during a long-term experimental

campaign.

In the short-term campaigns, the deposition rates ranged from

1.1.10-5 to 3.0.10-5 m.s-1 for glass specimens and from 4.2.10-5 to

1.2.10-4 m.s-1 for façade coating specimens. In the long-term

campaign, where test specimens were exposed to an urban

atmosphere for 8 to 12 months, the dry deposition rates mea-

for 131I, 137Cs and 103Ru, and 1 to 4 µm for 140Ba, 144Ce and 95Zr. For

aerosols with a mean aerodynamic diameter of 0.4 µm, the average

deposition rates on glass surfaces and walls were given as 8.2.10-5

m.s-1 and 1.2.10-4 m.s-1, respectively, with significant variations (of

more than one order of magnitude) depending on the radionuclide.

For aerosols with a mean aerodynamic diameter of 1 to 4 µm, the

average deposition rates on glass surfaces and walls were given as

1.5.10-5 m.s-1 and 8.7.10-5 m.s-1, respectively (Table 4) also with

significant variations in deposition rate depending on the radionu-

clide considered, which were difficult to explain for radionuclides

transported by natural aerosols (especially over long distances).

The average dry deposition rates determined during the SaliFa 1

campaign (glass: 2.9.10-5 m.s-1; coatings: 1.1.10-4 m.s-1) were close

to those resulting from Roed’s studies (glass surfaces: 8.2.10-5

m.s-1; walls: 1.2.10-4 m.s-1), particularly in the case of deposition

rates on walls. The average dry deposition rates determined during

the SaliFa 2 campaign were lower than for the SaliFa 1 campaign

(glass: 1.3.10-5 m.s-1; coatings: 4.6.10-5 m.s-1) but still in good agree-

ment with Roed’s results.

The average dry deposition rates determined during the long-term

experimental campaign (glass: 3.0.10-5 m.s-1; coatings: 2.1.10-4 m.s-1)

were close to those resulting from Roed’s studies.

Taking into account the measurement uncertainty associated with

1. 3

Reference data set Aerosol type Aerosol diameter (µm)Dispersion rate on

glass surfaces (m.s-1)Dispersion rate on

walls (m.s-1)

Short-term campaign: SaliFa 1

Fluorescein 0.2 2.9.10-5 1.1.10-4

Short-term campaign: SaliFa 2

Fluorescein 0.2 1.3.10-5 4.6.10-5

Long-term campaign 7Be 0.4 3.0.10-5 2.1.10-4

Roed 1986,1987 131I 0.4 2.3.10-4 3.0.10-4

Roed 1986,1987 137Cs 0.4 5.0.10-6 1.0.10-5

Roed 1986,1987 103Ru 0.4 1.0.10-5 4.0.10-5

Roed 1986,1987 140Ba 1 to 4 2.0.10-5 4.0.10-5

Roed 1986,1987 144Ce 1 to 4 — 9.0.10-5

Roed 1986,1987 95Zr 1 to 4 1.0.10-5 1.3.10-4

Table 4 Comparison of dry deposition rates obtained by Roed (1986, 1987) and those obtained during the SaliFa short-term and long-term campaigns.


1. 3

Acknowledgements

This study was funded by the French Ministry for Ecology and

Sustainable Development (through Ademe, the environmental

and energy management agency) and conducted in collabora-

tion with the National Center for Building Science and

Technology (CSTB, Nantes, Marne-la-Vallée and Grenoble), the

Interprofessional Research Center for Aerothermochemistry

(Coria, Rouen) and the Central Research Institute in Nantes

(ECN).

sured using 7Be ranged from 1.4.10-5 to 3.9.10-5 m.s-1 for glass

specimens and from 1.1.10-4 to 3.4.10-4 m.s-1 for coating speci-

mens. The results obtained with fluorescein aerosols for short

exposure times (1 hour) and with 7Be aerosols for long expo-

sure times (several months) are very similar.

Future studies will aim to quantify dry deposition as a function of

micrometeorological conditions (turbulent parameters), and to

accurately determine the associated impact of thermophoresis.

References

AFNOR NFX 44-011 (1972). Séparateurs aérauliques - Méthode de mesure de l’efficacité des filtres au moyen d’un aérosol d’uranine (fluorescéine), 12 p.

Boulaud and Renoux (1998). Les aérosols, Physique et Métrologie, Lavoisier TEC et DOC, 291 p.

D. Maro, D. Boulaud, A. Copalle, P. Germain, D. Hébert, L. Tenailleau (2004). Validation of dry deposition models for submicronic and micronic aerosols. Proceedings of 9th Int. Conf. on harmonization within Atmospheric Dispersion Modelling for Regulatory Purposes, Garmisch-Partenkirchen, p. 89-94, 1-4 June 2004.

J. Roed (1983). Deposition velocity of caesium-137 on vertical building surfaces, Atmospheric Environment., 17, 3.

J. Roed (1985). Run-off from roofs, Risö-M-2471.

J. Roed (1986). Dry deposition in urban areas and reduction in inhalation dose by staying indoors during the Chernobyl accident, paper presented at a meeting 12 june 1986 of the group of experts on accident consequences (GRECA), NEA/OECD, Paris.

J. Roed (1987). Dry deposition on smooth and rough urban surfaces, The post-Chernobyl workshop, Brussels, 3-5 February 1987, NKA/AKTU-245 (87)1.

C. Sacré, J.-P. Flori, D. Giraud, F. Olive, B. Ruot, J.-F. Sini, J.-M. Rosant, P. Mestayer, A. Coppalle, M. Talbaut, D. Maro, O. Connan, D. Hébert, P. Germain, M. Rozet (2006). Salissures de façade, Programme PRIMEQUAL, Rapport CSTB EN-CAPE 06.009, 54 p.


Context of atmospheric radioactivity monitoring programs

Artificial radionuclides were first considered as indicators of inter-

national nuclear weapons tests in the atmosphere, and subse-

quently as indicators of radioactive contamination [Bouisset et al,

2004]. Most of the radionuclides produced during nuclear tests(1)

have disappeared through radioactive decay due to their short

half-life. Cesium-137 (137Cs) is one of the main indicators (often the

only one) used by European and international atmospheric radio-

logical monitoring networks, particularly on account of its half-life

(30.2 years) and relative ease of measurement (by direct gamma

spectrometry). Figure 1 shows that during the period of atmo-

spheric nuclear tests (1945-1980), each test produced a rapid increase

in 137Cs activity, followed by a decrease by a factor of two in the next

six months, thus showing the importance of deposition mecha-

nisms.

Olivier MASSON, Damien PIGA, Philippe RENAUD, Lionel SAEY, Pascal PAULATContinental and Marine Radioecological Studies Laboratory

Anne DE VISME-OTTEnvironmental Radioactivity Measurements Laboratory

The year 2008 marks the 50th anniversary of the establishment in France of atmospheric radioactivity monitoring

programs to regularly monitor the presence of natural and artificial radionuclides in the atmosphere. These

programs rely on regular sampling and measurements of atmospheric suspended dust particles (aerosols) to

identify radionuclides present in the atmosphere and determine their current activity at adult height level. This

radioecological monitoring program integrates radiation protection objectives, including:

ensuring early detection of the arrival of radioactive plumes (alarm system);

ensuring the measurement of low-level reference values to assess the impact of recent contamination episodes,

regardless of magnitude.

Recent monitoring campaigns were based in particular on the detection of natural and artificial radionuclides

present in the atmosphere with a view to better assessing the potential long-term impact of accidental release.

This assessment relies on studies aimed at understanding the mechanisms underlying atmospheric transfers to

and from the terrestrial compartment. Current research seeks to identify the mechanisms that potentially delay

the return to initial conditions prior to an accidental release.

CONTRIBuTIONS OF ARTIFICIAl ATMOSPHERIC RADIONuClIDE MONITORINg to the study of transfer processes and the characterization of post-accidental situations

1. 4

(1) In particular, iodine-131, barium-140, ruthenium-103, ruthenium-106, cerium- 141, cerium-144, strontium-89, strontium-90, yttrium-91, zirconium-95, manganese-54, iron-55, and plutonium isotopes.


1. 4

1970 to 1986, measurement durations were multiplied by five. From

1980 to 1986, detection efficiency increased by a factor of four, and

from 1996 to 2002 it increased again by a factor of two. In addition,

from 1993 to 2004, detector background noise levels were reduced

by a factor of 10. All of these improvements proved to be necessary

to meet the objectives of "low-level" radiological monitoring programs,

since during the same period (from 1958 to 2008) aerosol-borne

artificial radioactivity levels decreased by a factor of 10,000.

Under severe reactor accident conditions, 137Cs would probably

be released to the environment, temporarily resulting in activity

concentrations in the atmosphere one or more orders of magni-

tude higher than current levels. During accident and post-accident

phases, an adequate knowledge of the contamination level prior

to the event could be used to quantify the impact of release to

the atmosphere.

The Chernobyl accident reloaded the atmosphere dramatically

(increase of average activity levels by a factor of 106 over a ten-

day period [Renaud et al, 2007]). In 1997, cesium-137 activity in

the atmosphere had dropped back to the same level as before the

accident, i.e. approximately 10-6 Bq.m-3. In late May 1998, the

incineration of a 137Cs source in Algeciras (Spain) multiplied the

activity concentration by 2,500 for a few days, but did not disrupt

the generally decreasing trend for any length of time.

This decrease in activity between two successive tests was used to

predict the 99% depletion of the radionuclide stock in the atmo-

sphere after only five to six years. Although still perceptible from

one year to another until the late 1990’s, this depletion has slowed

considerably due to a residual contribution via the resuspension of

radionuclides previously deposited on soils.

Figure 2 shows the radionuclides regularly monitored in France

based on samples collected by IRSN OPERA stations(2) during the

past six years.

137Cs is the only artificial radionuclide that is still frequently mon-

itored in the atmosphere in France(3). The ability to measure trace

quantities of cesium-137 (down to 10-8 Bq.m-3 of air) make it a

particularly valued means for characterizing past events, as well as

potential situations in the event of accidental release.

The annual average activity concentration of cesium-137 is cur-

rently 0.25 Bq per million cubic meters of air (0.25.10-6 Bq.m-3),

the lowest value ever observed since the beginning of the moni-

toring program. This average activity is derived from measurements

taken every ten days at nine sites in France. Each of these sites is

equipped with an OPERA aerosol sampling station.

Cesium-137 can only be detected by implementing specific devices

used to concentrate compounds present in trace quantities, and by

improving the sensitivity of measuring devices. From 1960 to 1980,

the quantity of air filtered per measurement was multiplied by 50,

and currently amounts to 70,000 m3 over a five-day period. From

1959

1961

1963

1965

1967

1969

1971

1973

1975

1977

1979

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007

10

10-1

10-2

10-3

10-4

10-5

10-6

10-7

10-8

1

Bq per m-3 of air

Fallout from atmospheric nuclear tests

Chernobyl accident

Algeciras incident

Figure 1 Cesium-137 activity in the air in France from 1959 to 2007. Aerosol samples taken by OPERA stations (the observatory for continuous monitoring of environmental radioactivity).

(2) Continuous environmental radiation monitoring network.

(3) In recent short-term studies, other artificial radionuclides (239Pu, 240Pu) were also detected at levels of approximately 10-9 Bq per m3 of air.



1. 4

depositions into the atmosphere, since their role was masked by

the predominant impact of the fallout from nuclear atmospheric

tests. The gradual disappearance of this contamination has made

it possible to identify these timeless mechanisms, which are now

recognized as being responsible for maintaining the long-term

persistence of activity in the lower layers of the atmosphere and

determining its variability.

In the absence of new atmospheric releases of 137Cs, the only

residual source is the "stock" accumulated over the years in soil.

Due to its affinity with clays and organic materials, 137Cs remains

for the most part in the first 10 to 15 centimeters of the soil. The 137Cs present in the soil surf

Documents

1environment Radioactivity and the · 2011. 7. 6. · 16 2008 Scientific and Technical Report - IRSN T he subjects covered in this report reflect IRSN’s scientific achievements