Transcript The development of composition and technology of amendment

The Dnieper River Aquatic System Radioactive
contamination:
Long-term Natural Attenuation and Remediation
O. Voitsekhovych,
G.Laptev, V.Kanients
UkrainianHydrometeorological
Inst.Kiev
[email protected]
and
Alexei Konoplev
Centre for Environmental Chemistry
“Typhoon”, Obninsk, Russia
[email protected]
1
Why Aquatic Ecosystem proposed for consideration
Dnieper Basin and other rivers were
significantly affected by Chernobyl radioactive
fallout during initial period.

Secondary contamination of waters can
last long, significantly extending the areas of
initial contamination. This is caused by
radionuclide dispersion via aquatic pathways
(infiltration, wash-out, water transport, bioaccumulation & bio-transfer….)

QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Aquatic pathways do not normally cause
significant human exposures (only in some
specific cases)

However, public perception of risks, which
may occur due to radioactive contamination of
water bodies as a role, is inadequate and
creates significant stress depended social
tenses.

Natural attenuation processes
NA - in many cases are key factors in self-cleaning of the water bodies
Speciation of soils and radionuclide behavior
• Mobility and bioavailability of radionuclides are determined by
ratio of (1) radionuclide chemical forms in fallout and (2) sitespecific environmental characteristics.  This determines (a) the
rates of leaching,(b) fixation/remobilization, (c) sorption-desorption
of mobile fraction (its solid-liquid distribution).
• The total distribution coefficient for radionuclides can vary in a
wide range (4 orders of magnitude for radiostrontium and 5 orders
of magnitude for radiocaesium) as a function of fallout
characteristics and environmental conditions.
• The total distribution coefficient for radionuclides is a dynamic
characteristic and depends on transformation rates of chemical
forms.
• To reduce uncertainty in the estimates and predictions of
radionuclide behavior, the exchangeable distribution coefficient
Kdex was suggested to be used instead of Kdtot.
Selective sorption and fixation of radiocaesium

High retention of radiocaesium in
soils is caused by two main
processes: selective reversible
sorption on illitic clay minerals and
fixation.

Advanced methods have been
proposed for determining the
capacity of selective sorption sites
(Frayed Edge Sites – FES) and
exchangeable radiocaesium
interception potential (RIPex).

FES
RES
KcFES (Cs / M )
137

FES  M  Cs 
FES137Cs  M 
Quantitative data were obtained for RIP ex(M )  Kdex(Cs) mM  KcFES(Cs / M )[FES]
a wide range of soils and bottom
sediments with respect to FES
capacities and RIPex.
4
137Cs
monitoring studies in rivers, lakes, bottom sediment
of reservoirs and Black Sea
Uncertainties in Assessment and Needs for Experimental
Verification of the accidental consequences
Radionuclide transport studies due to Runoff, sampling
at the contaminated lands and water bodies
20
Return water running
off from floodplain
and drainages
90
Sr, ТBq
90Sr
18
16
Inflow to ChEZ
Outflow from ChEZ
14
12
10
8
6
4
2
0
1987
9
137
1989
1991
Cs, ТBq
90Cs
8
7
6
5
1993
1995
1997
Year
1999
2001
2003
2005
In the Pripyat river, 1020% of Cs and 40-70%
of Sr originate the
washed out from the
ChNPP zone
Inflow to ChEZ
Outflow from ChEZ
4
3
2
1
0
Wash-off Snow
melting effect
1987
1989
1991
1993
1995
1997
Year
1999
2001
2003
2005
Pripyat River Floodplain around Chernobyl NPP was contaminated heaviest
It is most significant source of 90Sr secondary contamination in Dnieper system.
No significant impact by 137Cs, because high adsorption into the soil
Contamination
1986
Flood protective dam has been constructed
The most efficient water
protection is to control water
level and to mitigate inundation of
the most contaminated floodplains
by the flood protection sandy
dykes constructed at left and right
banks of the Pripyat river
1993
1999
Bq/m
3
1000
137Cs
in the
waters of the Dnieper reservoirs
Сs
137
137Cs
Vishgorod
Novaya Kahovka
100
10
1
1987
1989
1991
1993
1995
1997
1999
2001 Years
activity concentration in water
at the lowest reservoir returned to
pre-accidental level in 1996-1998.
In 2012, 137Cs activities in Kiev (upper
reservoir) & Kakhovka (lower
reservoir) in a cascade were at 10-15
Bq m3 & 0.5-1.0 Bq m3 range
137Cs
Bq/kg w.w. in freshwater fish (Kiev reservoirs
and most contaminated lakes near ChNPP)
137Cs
in predatory and non predatory fish species in Kiev reservoir (I.Ryabov et
al., 2002)
137Cs
and 90Sr in (a) predatory and (b) non-predatory fish
at Gluboky Lake
D.Gudkov, et al. 2008)
Collective Dose Commitment (CDC70) caused by 90Sr and
137Cs flowing from the Pripyat River (Berkovsky et al. 1996)
Region
Chernigov
Kiev
Cherkassy
Kirovograd
Poltava
Dnepropetrovsk
Zaporojie
Nikolaev
Kharkov
Lugansk
Donetsk
Kherson
Crimea
Total
Population,
(in millions of
people)
1.4
4.5
1.5
1.2
1.7
3.8
2
1.3
3.2
2.9
5.3
1.2
2.5
32.5
90
137
Sr
CDC 70 (man-Sv)
Cs
CDC70 (man-Sv)
4
290
115
140
130
610
320
150
60
15
330
100
175
2500
2
190
50
40
60
75
35
20
4
1
20
20
5
500
Ratio
Sr CDC70
137
( Cs CDC70)-1
2
1.5
2.3
3.5
2.2
8
9
8
15
15
17
5
35
5
90
Dose estimates for the Dnieper system: if there had been no action to reduce
radionuclide fluxes to the river, the CDC70 for the Ukraine population (mainly
due to Cs and Sr) could have reached 3000 man Sv.  Countermeasure works!
Protective measures, which were carried out during 1992–1993 on the left-bank
flood plain of the Pripyat River and later on right bank (1999) decreased
exposure by approximately 1000 man Sv. (Voitsekhovich et al. 1996).
Long-term dose assessment due to
exposure via aquatic pathways
Human exposure via the aquatic pathway took place as a result of
consumption of drinking water, fish catch in reservoirs and agricultural
products grown using irrigation water from Dnieper reservoirs.
Estimated individual doses for people living along the Dnieper cascade through
the aquatic pathways (far away from ChNPP) do not exceed 10 μSv y-1.
However, estimated collective doses are rather high. No alternative water
consumption. Stress component has to be primarily taken into consideration
when the water protection actions is planned.
Furthermore, in some closed lakes, the concentration of 137Cs remains high nin
both water and fish. People who illegally catch and eat fish may receive
internal doses of up to1 mSv per year from fish.
The most significant contribution to the individual doses from aquatic pathways
caused by 131I in the first week after the accident, but for very short time
(Maximal values about 140 Bq/l observed at the Kiev water intake plant 30 Apr
1986  Fukushima’s 150-250 Bq/l in a reservoir near Tokyo in March 2011)
Lessons learned
 Although the Chernobyl radioactive fallout affected the large scale
watershed areas and water bodies, the most of aquatic systems
returned to their pre-accidental status within first decade after the
accident. The main factors of self-rehabilitation of the water
bodies were naturally attenuation processes.
 Long-term radiological consequences for aquatic ecosystems will
be mainly determined only at the most heavy contaminated lakes
and wetlands at the Chernobyl NPP near zone.
 Many inadequate water protection measures were carried out
during initial post-accidental period because preparedness lacked,
data and decision making support tools were in use, environmental
radiation monitoring network has not been developed, impact of
social stress was huge, and inadequate risk perception took place.
 Scientifically defensive assessment tools and required data
must be developed and applied as a basis for sufficient
justification and water remedial actions optimization
Extra slide
Water protection and Remediation
Many remediation measures during initial period after the accident (19861988) were put in place, but because actions were not taken on the basis of
dose reduction, most of these measures were ineffective.

Because of the importance of short lived radionuclides (e.g., 131I), early
intervention measures, particularly changing supplies, can significantly reduce
doses to the population. However this opportunity has been missed during
first month since the accident.

During first months after the accident, restrictions on fishery and irrigation
from the contaminated water bodies have been established. Many actions for
the water regulation were applied at the small river in the Chernobyl exclusion
zone.

Numerous new countermeasures that were applied months and years after
the accident to protect water systems from transfers of radioactivity from
contaminated soils were generally ineffective and expensive and led to
relatively high exposures to workers implementing the countermeasures.

The only effective “late” countermeasure can be the water regulation at
the most contaminated floodplains and water runoff regulation from the
wetlands in the close zone around ChNPP.

Lessons learned cont’d
 Countermeasure and remediation selection must be based on a
cost-risk analyses that directly connects the main physical and
chemical processes to environment (ecosystem) or human heath
risks and costs
 Decision makers must be knowledgeable on phenomena being
evaluating, efficient in using expert’s experience and analytical
and modeling systems. Right and reasonable decisions should
mitigate or prevent expose of people, and should also allow
“more” safe within the limited resources available.
 Decision makers must communicate the facts quickly and
honestly to the affected public.
 Because the residual radioactive pollution still exists and our
knowledge yet are not exhaustive, it is reasonable to continue
research programs in ChNPP near zone as Unique Test site for
radioecological studies.
The aquatic ecosystem radioactive contamination story,
natural attenuation process and assessment for
effectiveness of the water protection
Y.Onishi, O.Voitsekhovych,
M.Zheleznyak
Chernobyl What Have we learned.
The Successes and Failures to
Mitigate Water Contamination
over 20 years.
Springer. 2007
http://www.springer.com/environment/book/978-14020-5348-1
Thank you very much for your attention
Duplicated slides
Fuel Particles in the Chernobyl fallout

Dominant part of radionuclides deposited on the soil
surface in the Chernobyl NPP vicinity was
incorporated within fuel particles.
Particles dissolution was the key process governing
radionuclides mobility and bioavailability in soils
during first years after the accident and several
decades if particles were deposited to the water
body sediments.
50
Portion of mobile forms, %

40
30
Sr-90 mobile, %
Cs-137 mobile, %
20
After B. Salbu
10
0
26.04
26-27.04
27-28.04
28-29.04
29-30.04
Date
1-2.05
2-3.05
3-4.05
20
Main messages from Chernobyl soil-water studies

Information on radionuclide deposition levels
alone is not enough to accurately predict future
and to assess human dose.
Data on speciation in fallout, rates of
transformation processes and site-specific
environmental characteristics determining these
rates are needed.

Information on radionuclide chemical forms, their
transformation in other words mobility and
bioavailability should be taken into account when
rehabilitation and decontamination strategies are
developed on local or regional scale.
21
Experiments on runoff plots
Snow melt wash-out studies
Artificial raining of the
contaminated catchments

Available are results of the study
radionuclides wash-off by rainfall
and snowmelt surface runoff.
These studies were conducted in
the contaminated territories on
the runoff plots of 1 m2 to 1000
m2.

Available are characteristics of
runoff plots, speciation and
content of 137Cs and 90Sr in soil,
rain and runoff hydrographs,
concentration of 137Cs and 90Sr in
solution and on suspended
matter in the run-off, and
chemical composition of run-off
and radionuclide speciation in
soil for selected runoff plots.
0.1
Kymijo ki
Ko kemaenjo ki
Oulujo ki
0.01
Kemijo ki
To rnio njo ki
(Borsilov and Klepikova 1993).
137
Calculated plume formation
according to meteorological
conditions for instantaneous
releases on the following dates
and times (GMT): (1) 26 April,
00:00; (2) 27 April, 00:00; (3) 27
April, 12:00; (4) 29 April, 00:00; (5)
2 May, 00:00; and (6) 4 May, 12:00
Cs in water per Bq m
-2
of fallout (m
-1
)
Radioactive contamination of the
catchments and aquatic environment
as versus of fallout formation date, its
physical and chemical forms and also
the landscapes at the deposited river
watersheds
Do ra B altea
Dnieper
0.001
So zh
Iput
B esed
P ripyat (M o zyr)
0.0001
Danube
P ripyat (Cher.)
0.00001
0
5
10
15
Time since Chernobyl (yrs)
137Cs
activity concentration in different rivers per unit of deposition, Smith, 2004
Radionuclides in Rivers
Annual averaged 137Cs in the Dnieper River
Cs, Bq.L -1
0,9
137
1,2
0,3
Ratio of 90Sr and 137Cs in soluble forms in Pripyat
River near Chernobyl
Uzh
Irpen
Teterev
0,6
0
0
5
10
15
Time, yr
1012 Bq Radionuclide inlet to the Kiev reservoir. Pripyat River
The 137Cs concentration
in river water has been
shown to be directly
proportional
to
the
relative fraction of its
exchangeable form in
the surface soil layer.
The
monitoring data
allowed
to
validate
mathematical models

Since 1991 to 2009
as result of several
high floods the most
of Cs-137 in bottom
sediment has been
removed with the
sediment particles
from the upper part
deposited area to the
down part sector of
the Kiev reservoir
Sedimentation is a key factor of 137Cs removal from the
water column to the bottom sediments
Upper part of Kiev Reservoir
1998
Low part of Kiev Reservoir
137Cs
1991-93
1994
1994
Kiev Reservoir
Data of UHMI
2009
137Cs-137
in the Black Sea
0
0
137
200
400
10
137
Cs, TBq
600
Cs, Bq m-3 20
800
1000
30
0
TOTAL
INVENTORY
(0-200m layer) 1173+/-181 TBq
50
100
Depth, m
150
200
137
Cs activity, Bq/kg
0
500
1000
1500
After Chernobyl 137Cs inventory in the 0-50
m layer increased by a factor of 6-10 and the
total 137Cs inventory in the whole BS basin
increased by a factor of at least 2 (preChernobyl value of 1.40.3 PBq after bombtesting fallout).

137Cs
2000
0.30-0.50
1986 (89)
Slice, cm
1.00-1.20
1.40-1.60
1.80-2.00
2.25-2.50
2.75-3.00
1963 (66)
Stations:
- BS98-16
- BS2K-37

0-0.15
0.70-0.90
C(z)=C0+a/(1+exp(-(z-z0)/b))
R = 0.91 St. Error = 2.61
input from the Danube and the Dnieper
rivers (0.05 PBq in the period 1986-2000)
was insignificant in comparison with the
short-term atmospheric fallout
Inadequate Radiation Risk Perception by Public was a key
reason in WATER PROTECTION ACTION PLAN implementing
During initial period after the Chernobyl
Accident the number of expensive
actions to reduce secondary
contamination of the rivers and
groundwater have been applied.
Dose realization (%) during a 70 years for
children born in 1986
For 1-st year about 47 %
For 10 years about 80%
Most of the actions were extremely
Years
expensive and ineffective.
From I. Los, O. Voitsekhovych, 2001
Actual dose
Public perception about
Food product, milk
water
external
inhalation
In spite of doses were estimated
to be very low, there was an
inadequate perception of the
real risks by Public using
water from contaminated
aquatic systems.
This factor made reasonable to
justify some set of limited
water remediation actions to
reduce Public stressing and
prevent further long term
surface water contamination of
the Pripyat