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Cs-137 versus stable K in root uptake from radioactively
contaminated soils: field observations
Tatiana Paramonova, Vladimir Belyaev
Soil Science & Geography Faculties of Moscow Lomonosov State University,
Moscow, Russia
Analogies and differences between Cs-137 and stable K (K-39) bioavailability for crops growing on radioactively contaminated lands are still under discussion.
To clarify the peculiarities of Cs-137 and K root uptake and the elements distribution over the parts of plant biomass the field observations within post-Chernobyl Plavsky radioactive hot spot (Tula region, Russia) have been examined.
Outline
137Cs deposition within Eastern Europe after
Chernobyl accident (April 26, 1986)
Outline
Moscow
Atlas of 137Cs depositon on Europe after The Chernobyl accident / M. De Cort et all., 1998
≈350 km
Russian radiation safety standard for 137Cs - 37 kBq/m2
Plavsky radioactive hotspot,
Tula region 137Cs deposition 185-555 kBq/m2
Plavsk
Outline
Landscapes of Plavsky radioactive hotspot
Outline
EU Soil Map by Prof.Dr.H.E. Stremme
A+AB ~60-80 cm
Corg 4.9-7.3%
pHw 6.2-6.7
dV1.1-1.2 g/cm3
loamy texture
Soil cover of Plavsky radioactive hotspot
Objectives:
What are peculiarities of Cs-137 and K root uptake from soils of radioactively contaminated areas – whether they biochemical analogs or not?
Sampling area and plots
Watersheds and low-gradient hillslopes, 213-248 m ASL
Floodplain, 194 m ASL
maize rape potatoes
barley dry meadow wet meadow
Lower parts of hillslopes, 208-211 m ASL
Methodology
4 agricultural crops of field rotation (spring barley, maize, potatoes, and rape) and
semi-natural vegetation of dry and wet meadows were selected for the study.
Soil sampling
Methodology
Above- and belowground parts of biomass
were separated for the detailed examination.
Methodology
Vegetation sampling – aboveground parts
Methodology
Vegetation sampling – belowground parts
Methodology
The control of washing out soil particles with optical microscopy.
Total Cs-137 and stable K (K-39) were
analyzed in aboveground and belowground
biomass of vegetation.
Total Cs-137 and non-exchangeable stable K
(2 n HCl extraction) were analyzed in soils
that resulting in comparability of their
bioavailability for plants.
Methodology
137Cs and K in soils Results
Soil Altitude,
m ASL Cs-137
Bq/kg
Knon-ex,
%
barley 248 486 0.09
maize 248 459 0.41
rape 245 494 0.11
potatoes 213 674 0.10
dry meadow chernozem 208 712 0.12
wet meadow alluvial
calcareous 194 621 0.11
Determined current activities of Cs-137 in arable and native chernozems of the area taking into
account initial level of contamination and the relief position varied from 460 Bq/kg to 710 Bq/kg
(170-280 kBq/m2). The amount of non-exchangeable K in rhizosphere represented 0.09-0.14%
without mineral fertilizers and 0.40% after soil fertilization (for maize).
Profile distribution of 137Cs and K in soil
Results
Cs-137, Bk/kg
0 500 1000 1500 2000
barley
maize
rape
potatoes
dry meadow
wet meadow
0-10 cm
10-20 cm
20-30 cm
Knon-ex , %
0,0 0,2 0,4 0,6
barley
maize
rape
potatoes
dry meadow
wet meadow
0-10 cm
10-20 cm
20-30 cm
137Cs and K in vegetation
Results
Agrosystem /
natural ecosystem Cs-137, Bq/kg K, %
barley 37 0.4
maize 58 2.1*
rape 5 0.9
potatoes 31 1.1
dry meadow 73 0.3
wet meadow 120 0.3
* - mineral fertilizers have been used for maize agrosystem.
To avoid the difference in Cs-137 and K
content in soils of different plots and to
appreciate the biological peculiarities of
individual crops the transfer factor (TF)
values (the ratio of the activities for Cs-137
and concentrations for K between vegetation
and in soil) were calculated.
Results
Transfer factors for 137Cs and K Results
Agrosystem /
natural ecosystem TFCs-137 TFK
barley 0.06 3.8
maize 0.13 5.1
rape 0.01 8.4
potatoes 0.05 12.9
dry meadow 0.10 2.0
wet meadow 0.19 3.0
TFCs-137 : wet meadow > maize, dry meadow > barley, potatoes > rape
TFK : potatoes > rape > maize, barley > wet meadow, dry meadow
As a whole, TFK were several orders more than
TFCs-137 that stressed the biogenic nature of
potassium and the xenophobic nature of caesium.
Among the investigated agricultural crops and
meadow plant communities TFK were minimal for
maize and barley, middle – for rape, dry and wet
meadows, and maximal – for potatoes (17.4).
TFCs-137 were minimal for rape, middle – for wheat,
barley and potatoes, and maximal – for maize, dry
and wet meadows.
Results
Results Transfer factors in above- and belowground parts of
biomass for 137Cs and K
TFK
20
15
10
5
0
5
10
15
20
barle
y
maize
rape
pota
toes
dry
mea
dow
wet
mea
dow
aboveground biomass belowground biomass
TFCs-137
0,25
0,20
0,15
0,10
0,05
0,00
0,05
0,10
barle
y
maize
rape
pota
toes
dry
mea
dow
wet
mea
dow
aboveground biomass belowground biomass
An accounting of Cs-137 and stable K distribution among above- and belowground parts of plant biomass clearly demonstrated the importance of biological characteristics in root uptake of the elements: wheat, barley and maize (Gramíneae family) were characterized by elevated Cs-137 activities in belowground parts (12-14 times higher than in shoots), and rape (Brassicaceae family) and potatoes (Solanaceae family) were characterized by homogenous distribution of the radionuclide over plant biomass, whereas K concentrations in aboveground parts of plants were 1.5-10 times greater than in belowground parts of plants for all investigated crops.
Results
Conclusion
Root uptake of the elements was characterized by different peculiarities. Thus, Cs-137 and stable K were difficult if not impossible to consider as biochemical analogists in root uptake from radioactively contaminated soils.
The study was supported by
the Russian Foundation for Basic Research
(project no. 14-05-00903).
Acknowledgements
Thank you for attention!