earlier CRP upper limit
DIFFERENT GREEK SOIL TYPES
5. DEVELOPMENT OF APPROACH FOR CLASSIFICATION OF RUSSIAN SOIL ON THE BASIS OF RADIONUCLIDE TRANSFER FACTORS FROM SOIL TO CROPS
6.1. Characteristics of data samples for 137 Cs and 90 Sr transfer factors in the classification systems developed
The characteristics of samples for 137Cs and 90Sr transfer factors in barley were assessed for each cluster of the classification systems. To this end, distributions of values for classification characteristics (exchangeable K, pH, etc.) were analysed. In the event of bimodal distribution, the initial cluster that contained TF values was divided into two clusters. Differences in the geometric means for transfer factors between different clusters are readily explained with current knowledge of the mechanisms responsible for radionuclide behaviour in soil. The information presented in Tables 17–21 confirms the legitimacy of all the classification systems developed. To identify the best system, requires further investigation on a larger dataset.
TABLE 17. CHARACTERISTICS OF SAMPLES OF 137Cs TFs IN BARLEY FOR EACH CLUSTER OF THE SOIL TYPE – EXCH. K CLASSIFICATION SYSTEM
Soil characteristics Transfer factor
Soil group Soil type Exch. K Geometric mean 95% conf. level Range
0.44–0.94 0.0083 0.0029 0.004–0.023
Clay
1.1–1.94 0.0058 0.0016 0.00067–0.011
0.34–0.4 0.026 0.018 0.012–0.043
Loam
0.6–0.7 0.020 0.0068 0.012–0.035
0.1–0.19 0.031 0.021 0.023–0.055
Mineral soils
Sand
0.31–1.07 0.024 0.018 0.007–0.055
Organic soils Peat 0.18–0.53 0.034 0.029 0.014–0.1
TABLE 18. CHARACTERISTICS OF SAMPLES OF 137Cs TFs IN BARLEY FOR EACH CLUSTER OF THE SOIL TYPE –pHKCL CLASSIFICATION SYSTEM
Soil characteristics Transfer factor
Soil group Soil type pHH2O Geometric mean 95% conf. level Range
5.2–6.5 0.0075 0.0020 0.00067–0.023
Clay
7.1–7.9 0.0051 0.0016 0.004–0.0085
5.4–5.6 0.026 0.010 0.017–0.035
Loam
5.8–6.9 0.021 0.010 0.012–0.043
4.6–4.9 0.021 0.020 0.007–0.053
Mineral soils
Sand
5.7–5.9 0.036 0.018 0.023–0.055
Organic soils Peat 4.8–5.1 0.034 0.029 0.014–0.1
TABLE 19. CHARACTERISTICS OF SAMPLES OF 90Sr TFs IN BARLEY FOR EACH CLUSTER OF THE EXCH. Ca – ORGANIC MATTER (OM) CLASSIFICATION SYSTEM
Soil characteristics Transfer factor
Soil group Exch. Ca Organic matter Geometric mean 95% conf. level Range
0.6–1 0.20 0.031 0.16–0.25
TABLE 20. CHARACTERISTICS OF SAMPLES OF 90SrTFs IN BARLEY FOR EACH CLUSTER OF THE SOIL TYPE – ORGANIC MATTER (OM) CLASSIFICATION SYSTEM
Soil characteristics Transfer factor
Soil group Soil type Organic matter Geometric mean 95% conf. level Range
1.6–1.9 0.098 0.029 0.056–0.21
TABLE 21. CHARACTERISTICS OF SAMPLES OF 90SrTFs IN BARLEY FOR EACH CLUSTER OF THE SOIL TYPE - EXCH. Ca CLASSIFICATION SYSTEM
Soil characteristics Transfer factor
Soil group Soil type Exch. Ca Geometric mean 95% conf. level Range
10.4–19.2 0.089 0.026 0.049–0.21
Clay
20–28 0.052 0.0079 0.054–0.073
6–9.1 0.16 0.032 0.12–0.22
Loam
16.6–20 0.087 0.0025 0.085–0.089
2.4–4.9 0.173 0.068 0.093–0.25
(1) In the soil-plant system, soil properties influence the behaviour of 90Sr and 137Cs in various ways.
The main parameter, which describes the rate of radionuclides accumulation in farm crops, is the transfer factor (TF). Therefore, the transfer factor can be used for radioecological classification of soils.
(2) Regression equations have been derived that describe the effects of soil properties on 137Cs and 90Sr TFs to barley and cabbage with high multiple correlation cofficients. When developing such regression models, linear relationships are preferable but it is advisable to test for non-linearity.
(3) Based on statistical (correlation and factor) analyses, ratings have been established for variables that can be used for soil radioecological classification, which reflects the rates of 137Cs and 90Sr uptake by crops.
(4) On the basis of the statistical analyses of data, two schemes of soil classification have been developed based on 137Cs transfer factors for barley: classification system 1 using soil group (organic–
peat, mineral), mechanical composition (physical clay content) and рH value; classification system 2 using soil group (organic–peat, mineral), mechanical composition (physical clay content) and content of exchangeable K.
(5) For soil radioecological classification based on the rate of 90Sr uptake by plants, three schemes of soil classification have been developed: classification system 1 using soil group (organic–peat, mineral), content of exchangeable Ca and content of organic matter; classification system 2 using soil group (organic–peat, mineral), mechanical composition (physical clay content) and content of organic matter; and classification system 3 using soil group (organic–peat, mineral), mechanical composition (physical clay content) and content of exchangeable Ca.
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Atomic Energy Commission of Syria, Damascus, Syrian Arab Republic
Abstract
Transfer factors (TFs) for 137Cs were measured in two soils with a range of annual crops and olives. The values were towards the lower end of the ranges reported in the literature. Fertilization reduced TFs by 13–33%. TFs to the edible parts of arable crops were in the order cereals < broad beans, cucumber < leafy crops ≤ potato tubers.
Olive oil contained a lower 137Cs concentration than any of the other food products.
1. INTRODUCTION
The possibility exists of an accident that may release radioactive material into the environment. As nuclear facilities are not normally sited in densely populated areas, the adjacent land is likely to be agricultural or at least rural. Furthermore, the accident at Chernobyl in 1986 showed that agricultural practices could be affected within hundreds and even thousands of kilometers from the accident site.
Therefore, contingency plans are needed to consider countermeasures that can be used to reduce contamination of agricultural products, even in countries without nuclear power.
The two main considerations in preparing an agricultural counter measures strategy are to:
- protect human health by reducing radioactive contamination of agricultural products; and - return the land to normal usage as far as possible.
Different countermeasures are available to reduce or prevent transfer of radionuclides through the food chain. However the countermeasures vary in both effectiveness and their economic, ecological and social impact [1].
One of the countermeasures to be applied in the medium and long term is change of land use [2]. For example alternative crops could be grown that accumulate lower levels of the contaminating radionuclide than the crops usually grown in the areas under consideration. Another possibility is to grow crops such as olive trees where the edible product accumulates low amounts of radionuclides that are further reduced by processing.
There is little information on the transfer of anthropogenic radionuclides to plants and the food chain in semi–arid and arid regions, compared to humid and temperate regions. The climate in Syria varies from humid to extra–arid and soil properties also differ, depending on geological and climate conditions. It is therefore important to evaluate Syrian agricultural products as sources of internal dose by ingestion. As a part of this process the present research was carried out to determine the transfer factor of 137Cs from different soils to different crops in Syria.
2. MATERIALS AND METHODS