earlier CRP upper limit
DIFFERENT GREEK SOIL TYPES
2. MATERIALS AND METHODS 1. Climate
3.6. Dose assessment
The dose from consumption of black cabbage was calculated by two different methods, using the determined activity concentrations of 137Cs in soil samples (Bq/kg d.w.) for 2002 in Rize and applying TF values from the Chernobyl contaminated soils (Method 1) and also using concentrations in black cabbage samples collected from the same region in the same year (Method 2) and applying the consumption rate in the region.
3.6.1. Calculation of doses Method 1.
The dose was calculated using the following formula:
DCs (Black cabbage) = Cs Cf Fp Fh Fe Df 1.2·× 10-8 (man Sv) [5] (1) where
DCs is the collective committed effective dose from 137Cs by consumption of black cabbage from intake during 2002,
Cs is the 137Cs mean activity of soil samples,
Cf is the mean value of the Transfer Factor of 137Cs in black cabbage samples, Fp is the production of black cabbage in the region from the regional commercial
association (about 20 000 000 kg per year),
Fh is the fraction of the production which goes for regional human consumption (assumed to be 0.9),
Fe is the fraction actually eaten (assumed to be 0.8),
Df is the delay factor between production and consumption time and is calculated to be 0.9,
1.2·× 10-8 is the factor used for the committed effective dose calculation [6], and DCs (black cabbage) = 135 × 0.36 × 20 000 000 × 0.9 × 0.8 × 0.9 × 1.2 ×·10-8
= 7.55 (man Sv)
= 755 nSv/person
Method 2.
The dose was calculated using the following formulae:
Eingk = CCsk Hk DFing [7] (2)
where
Eingk is annual effective dose from consumption of 137Cs radionuclide in black cabbage (k) for 2002 (Sv yr-1),
CCsk is mean concentration of 137Cs radionuclide in black cabbage (k) (Bq kg-1 w/w),
Hk is consumption rate for black cabbage (kg yr-1) from the regional commercial association, DF is dose coefficient for ingestion of Cs radionuclide (Sv Bq-1)(1.3·10-8 is factor used
for the annual effective dose calculation), and Eing (black cabbage) = 6.6 × 12 × 1.3·× 10-8
= 0.000000767 Sv
= 767 nSv /person 4. DISCUSSION
The TF value of 137Cs in black cabbage in the sheltered plot was significantly higher in June 2000 than those under open conditions with same or different soils. During summer the temperature in the sheltered plot about was 5ºC higher than in the open plot. In previous studies 137Cs concentration, especially in vegetative plant parts, increased with increasing temperature during the growing season [8–9]. On the other hand, the TF value in flood soil is significantly higher than those obtained in local and sheltered local soil samples in February 2001. However, the TFs were lower in September 2002.
This implies that the biokinetics (uptake and loss) of 137 Cs in black cabbage also depends on climatic conditions. The effect of temperature also showed the TFs in maize under sheltered conditions.
In general, The TF values in maize grain, maize straw, sunflower grain and lettuce are higher in the flood soil than in the local soil. However, the TF value in white cabbage of the local soil is significantly higher than that from the flood soil. It is well known that variation in growth rate and in root surface area is important for radiocaesium uptake [10]. It is also well known that the TF value depends on soil properties such as pH, exchangeable K, organic matter content, mineral composition, etc [11]. The TF values in black cabbage did not show similar trends under artificially and Chernobyl
contaminated area was carrier-free. For this reason, the mean TF value of the 137Cs in the black cabbage samples under Chernobyl conditions was found to be 60 times higher than artificially contaminated 137Cs experiment with carrier. A previous study indicated that there was correlation between TF for radiocaesium and stable caesium [12]. Another study also indicated that the distribution coefficient, kd was reduced after a small addition of stable caesium [13].
In 1986, the highest value of 137Cs in black cabbage leaves was 80 Bq kg-1 (wet weight) from the eastern Black Sea region of Turkey [14]. In the present report, the mean 137Cs concentration was 6.6 Bq kg-1 (wet weight). We calculated the annual effective dose from consumption of black cabbage in 2002 as 755 or 767 nSv/person. In previous studies, we also calculated the annual effective doses from tea and anchovy consumption for 137Cs and 210Po in 1986 and 1997 which were 0.4 and 0.2 mSv/person, respectively [15–16].
The TF values of 85Sr in studied crops in the flood soil decreased in the order: parsley > black cabbage
> white cabbage > lettuce > maize straw > maize grain. The TF values in the local soil crops were in the order: black cabbage > parsley > white cabbage > lettuce > maize straw > maize grain. The exchangeable calcium level in local soil was higher than in the flood soil. For this reason, the TF values in parsley and maize straw in the local soil are significantly lower than in the flood soil. On the other hand, this relationship in black cabbage, white cabbage, lettuce and maize grain samples not significant. The TF values in black cabbage in the two types soils significantly decreased from February to April in 2001. Previous studies indicated that the availability of soil 90Sr to plants gradually decreased with time and also depends on the climatic conditions [8, 17].
5. CONCLUSIONS
Sixteen years after the deposition from the Chernobyl accident, the 137Cs is still located in the upper soil layers (0–10 cm). The vertical migration appears to be slow. On the other hand, about 10% of the radionuclide has been transferred into plants, especially green vegetables in 2001 and 2002. At the same time, isotopic exchange had not been extensive due to the low concentration of the stable caesium (133Cs). We conclude that the determination of stable Cs concentrations in soil and plant samples may necessary for the prediction of 137Cs uptake.
Ingestion of radionuclides in foods is an important part of the total dose received by a person [7]. For this purpose, we calculated annual effective dose (use of TF value) by consumption of black cabbage in the Chernobyl contaminated area.
In general, soil to plant transfer factors of 137Cs, 85Sr and 210Po were higher from the flood soil than the local soil and the sheltered local soil. The mean TF values of 137Cs in black cabbage were calculated to be 0.006, 0.004 and 0.005 in flood, local and sheltered local soil samples, respectively. The lowest TF value of 85Sr was 0.357 in lettuce in the local soil type whilst the highest value was 2.9 in parsley in the flooded soil type.
REFERENCES
[1] FRISSEL, M.J. (Ed.), FAO/IAEA/IUR, Protocol for Coordinated Research Programme on the Classifications of Soil Systems on the Basis of Transfer Factors of Radionuclides from Soil to Reference Plants. (1998).
[2] TOPCUOĞLU, S., et al., The influence of Chernobyl on the radiocesium contamination in lichens in Turkey, Toxicol. Environ. Chem. 35 (1992) 61–165.
[3] TUZUNER, A. (Ed.), Laboratory Handbook of Soil and Water Analysis, General Manager of Village Employment, Ankara (1990) (in Turkish).
[4] STRICLAND, J.D.H., PARSONS, T.R., A practical handbook of sea water analysis.
Bull.Fish.Res.Bd.Can.,167 (1972) 1–312.
[5] INTERNATIONAL ATOMIC ENERGY AGENCY, Sources of radioactivity in the marine environment and their relative contributions to overall dose assessment from marine radioactivity, IAEA-TECDOC-838, Vienna (1995).
[6] COMMISSION OF THE EUROPEAN COMMUNITIES, The Radiological exposure of the population of the European Community from Radioactivity in North European Marine Waters-Project Marina, Report Eur 12483, (1989).
[7] INTERNATIONAL ATOMIC ENERGY AGENCY, Safety Report, Generic models for use in the control of radioactive discharges into the environment, Working Material, Draft Safety Report Revised Safety Series-57, (2000).
[8] NORDIJIK, H., et al., Impact of ageing and weather conditions on soil-to-plant transfer of radiocesium and radiostrontium, J. Environ. Radioact. 15 (1992) 277–286.
[9] PAASIKALLIO, A., et al., The transfer of cesium-137 and strontium-90 from soil to crops after Chernobyl accident. Sci. Total Environ. 155 (1994) 109–126.
[10] SMOLDERS, E., et al., Analysis of the genotypic variation in radiocesium uptake from soil, Plant and Soil 155/156 (1993) 431–434.
[11] FRISSEL, M. J., et al., Generic values for soil-to- plant transfer factors of radiocesium, J.
Environ. Radioact. 58 (2002) 113–128.
[12] SHAW, G., BELL, J.N.B., The Kinetics of cesium absorption by roots of winter wheat and the possible consequence for the derivation of soil-to-plant transfer factors for radiocaesium, J. Environ. Radioactivity, 10 (1989) 213-231.
[13] SALT, C.A., MAYERS, R.W., Plant uptake of radiocaesium on heather moorland grazed by sheep, J. Appl. Ecol. 30 (1993) 235–246.
[14] TURKISH ATOMIC ENERGY AGENCY, Radiation and radioactivity measurements in Turkey after Chernobyl, Ankara, Turkey, (1988).
[15] UNLU, M.Y., et al., Natural effective half-life of 137Cs in tea plants, Health Phys. 68 (1995) 94–99.
[16] INTERNATIONAL ATOMIC ENERGY AGENCY, To establish and compare for the coastal waters of Turkey, the 210Po-210Pb contents in anchovy fish and sea snails, Contract No:9712/RO, Final Report, (2001).
[17] CLINE, J.F., Aging effects of the availability of strontium and cesium to plants, Health Phys.
23 (1981) 317–324.
TRANSFER FACTORS OF RADIONUCLIDES FROM SOILS TO REFERENCE