Uptake of radionuclides by spring wheat and barley from cultivated soils supplemented by contaminated sewage sludge Marketta Puhakainen and Toivo Yläranta Puhakainen, M. & Yläranta, T. 1992. Uptake of radionuclides by spring wheat and barley from cultivated soils supplemented by contaminated sewage sludge. Agric. Sci. Finl. 1: 27-36. (Finnish Centre for Radiation and Nuclear Safety, Box 268, SF-00101 Helsinki, Finland and Agric. Res. Centre of Finland, Inst. Environ. Res. SF- -31600 Jokioinen, Finland.) After the accident at the Chernobyl nuclear power station in April 1986, large amounts of fallout radionuclides originating from Chernobyl were measured in sewage sludge in Finland. Field experiments were performed to evaluate the amount of activity of fallout nuclides transferred from soil to spring wheat and barley grown in fields supplemented by contaminated sewage sludge and further to calculate the soil-grain transfer factors. The experiments were conducted in southern Finland on clay, clay loam and sandy loam soil. The digested sludge was spread on fields, at a ratio of 22 tons of dry matter per hectare. The sludge formed in 1986 was spread in spring 1987 on ploughed fields before the preparation of the seedbed, or in autumn 1987 prior to ploughing. The different plots were fertilized with NPK fertilizer so that the amount of available nutrients was about equal in all treatments. Application of sludge increased the concentration of 137Cs in grain 2-12 times as compared with crops grown in plots without sewage sludge addition. The transfer factor of l37Cs from soil to plant defined as Bq ha" 1 in plant (grain and straw) per Bq ha" 1 in soil (and sludge) varied in the first experimental years (1987 and 1988) from 20 x 10"6 to 150 x 10"6 and in the second experimental years (1988 and 1989) from 6 x 10"6 to 50 x 10"6 for sludge treated soil and from 10 x 10 6 to 60 x 10"6 and from 8 x 10"6 to 50 x 10"6 for soil without sludge addition, respectively. Key words: l37Cs, 134Cs, sewage sludge, spring wheat, barley Introduction After the accident at the Chernobyl nuclear power station in April 1986, large amounts of fallout radionuclides originating from Chernobyl were measured in sewage sludge in Finland (Puha- kainen et al. 1987). The highest measured 137Cs activity was 12 000 Bq kg ' dry matter (compared to l37Cs activities in sludge varying from 0-20 Bq kg" 1 dry matter before the accident) (Puhakainen 1986). Yearly 1 100 000 m 3 dewatered sewage sludge is produced in Finland. Of this, 75 % is utilized; 50 % in agriculture and 25 % for land- scaping. The maximum amount of sludge recommended for agricultural use was at that time 20 metric tons of dry matter per hectare. If the maximum amount of sludge accumulated in 1986 would have been spread on the fields, the increase of radioactivity would at most have been 24 000 Bq nr2 . In 1987, field experiments were started to evaluate the amount of activity of fallout nuclides 27 Agric. Sei. Finl. 1 (1992) https://www.c-info.fi/en/info/?token=YZ0EgjX3mqChsq4i.OtwxcjQ-igKCl0ueEPSrqg.mDrFeGjsS54MJJegjHlZJnM9jVV64Jr6hpL-6YCOImJ9_yJ4nUmC1qG6qIJvVnq2FloSwQJlpCwRrtTp2syo1gc_RfVd0ZozqpfrdO9U4CHf9IdAtnTbGFpw0kOHlT0nf4kfImn84JUgadhFFkDS-Dtq6DFUCljgknorgYwa7kwgFXpdqUjMeGlvIFn2B1MeEFr4Jzo2vU5DpyMe-pxHF-6pXzW4SsPNoHUtuuAiSQyX6Lv7adAEkQmngaI45CPSHu-NszLTAF3uS2dvdUf_R7yQpSsnCJBnWcMIRheN2M3qAA transferred from soil to spring wheat and barley grown in fields supplemented by sewage sludge. Knowledge of the interaction between sludge, soil and plants is required when recommendations regarding the utilization of sludge for agricultural purposes are given in the future. The experiments were conducted at the Agricultural Research Centre ofFinland at Jokioinen in southern Finland in 1987- 1989 on a clay, a clay loam and a sandy loam soil. Maiiiial and methods The sludge used in the experiments In the experiment dewatered digested sludge from the Kyläsaari wastewater treatment plant in Helsinki was used. Kyläsaari is the largest treatment plant in Finland, with over 100 m 3 of digested dewatered sludge being produced daily (Lundström 1987). After the accident the activity concentrations of the sludge in Kyläsaari were at most above 5000 Bq kg"' dry weight. About half of this activity was due to the precipitate coming from a water treatment plant. The flocculation with aluminium sulphate at surface water treatment plants during water purification was found to concentrate radionuclides originating from fallout relatively efficiently. This precipitate was pumped into the sewer system. A small amount of the precipitate rich in radio- nuclides doubled the concentration of l37 Cs in the sewage sludge (Puhakainen et al. 1987). The sludge formed in spring 1986 was used for the field experiments. The l37Cs activity con- centration in the sludge used was 5300 Bq kg" 1 dry matter in experiment 1 and 4700 Bq kg -1 dry matter in experiment 2, and the ratio l34Cs/ l37Cs was 0.6 (ref. day 1. May, 1986). The dry matter content in the dewatered sludge was 22 % and pH(H 2 0) 6.9. The chemical composition of the sewage sludge is given in Table 1. Extraction of radionuclides from the sewage sludge and precipitate with aluminium sulphate was done with acid ammonium acetate solution (pH 4.65). The extraction time was 1 h and the sludge to solution ratio 1:10 (7v) (Vuorinen and Mäkitie 1955). The activity of liquids and residuals were measured by Ge(Li) gamma- spectrometry. The extractability of radiocesium from the sewage sludge was 3-5 % and from the precipitate with Al-sulphate about 3 %. The precipitate was also frozen and defrozen before extraction. The freezing did not change the extractability of radiocesium (Toivanen 1987). Table 1.The chemical composition ofsewage sludge on a dry weight basis made by Soil Analysis Service Ltd. Analysed according to Finnish requirements (Ympäristöministeriö 1991). Element Method of Element Method of % analysis mg kg' 1 analysis Total N 2.4 SFS 5505'» B 43 SFS 3044,3047 Extr. N 0.26 SFS 5505 Cu 380 P 3.7 SFS 3044,3047 Mn 390 K 0.1 " Zn 1100 Ca 2.0 " Mo 1.5 Mg 0.3 " Co 19 S 0,9 2> Cr 94 Fe 14 SFS 3044,3047 Cd 3.7 Al 2.1 Ni 91 pH(H 20) 6.9 SFS 3021 Hg 0.26 ISO 5666/l 3> Dry matter 22% SFS 3008 Ph 120 SFS 3044,3047 1) =SFS standard, available from Suomen Standardisoimisliitto SFS, Box 205, 00121 Helsinki, Finland 2) =Hesse, P.R. 1971. A textbook ofsoil chemical analysis. John Murray (Publishers) Ltd. 520 p. 3) = International Standard (ISO, International Organization for Standardization) 28 Agric. Sei. Finl. 1 (1992) Field experiments The field experiments were conducted during two growing seasons on a clay, a clay loam and a sandy loam soil. The crops were spring wheat (cv. Ruso) and barley (cv. Kustaa). The size of the ex- perimental plots was 2.5 m x 15 m, replicated four times. The sludge formed in spring 1986 was spread in spring 1987 on ploughed fields before the preparation of the seedbed (experiment 1) or in autumn 1987 prior to ploughing (experiment 2). The amount of sludge used was 100 m 3 per hectare. This amount contained 22 metric tons of dry matter per hectare. The plots where no sludge was added were fertilized at a rate of 600 kg per hectare with a NPK fertilizer containing 16 % N, 7 % P and 13.3 % K. To the plots to which sewage sludge was added also 200 kg per hectare of a NPK fertilizer containing 20 % N, 4.4 % P, 8.3 % K was added. Hence, the amounts of plant available nutrients were about equal in all treatments. The residual effect of sewage sludge applications was studied in 1988 and 1989, respectively. Samples were takenfrom soil, sludge, grain and straw. Soil samples were taken before addition of sludge and cored to depths of 0-20 cm and 20-40 cm. The samples were dried at 35°C, and ground, avoiding disintegration of primary particles, through a 2-mm sieve and analyzed for volume weight, pH(CaCl2) (Tares and Sippola 1978), content of organic carbon (Sippola 1982) and gammaradionuclides (Table 2). The pH was measured in 0.01 M CaCl2 suspension at the soil to solution ratio of 1:2.5 (Tares and Sippola 1978). The measurements of radioactivity concentrations were carried out at the Finnish Centre for Radiation and Nuclear Safety. The samples were packed in Marinelly beakers (volume 0.6 1) and measured by low background Ge(Li) gamma- spectrometry. Grains and straws collected in 1987 were measured by direct gamma measurement in Marinelly geometry. In 1988, the activity con- centrations were so low that some of the samples Table 2. The mean concentration and ranges of l34Cs, l37Cs, (Bq kg" 1 dry matter) and the value of pH and volume weight and content ofclay and soil organic carbon in dry soil before the sludge was added, ref. day 1.10.1987. The results are the mean on 16 different plots. volume weight clay". Organic C pH 134Cs, Bq kg' 1 137Cs, Bq kg' 1 g cm 3 % % (CaCl,) mean range mean range Experiment 1 clay soil 0-20 cm 1.0 61 3.7 5.5 5.0 (3.1-7.3) 20 (15-27) 20-40 cm 1.0 73 2.0 5.6 7.2 (0-13) 26 (10-40) sandy loam soil 0-20 cm 1.2 13 2.6 6.3 6.8 (4.5-12) 24 (17-38) 20-40 cm 1.3 20 0.5 6.1 2.9 (0-5.2) 11 (1.2-18) Experiment 2 clay soil 0-20 cm 1.0 49 2.8 5.5 6.3 (2.2-11) 22 (12-34) 20-40 cm 1.1 61 1.3 5.7 2.2 (0-4.1) 8.4 (3.6-16) clay loam soil 0-20 cm 1.1 36 2.7 6.2 5.9 (2.6-11) 21 (11-35) 20-40 cm 1.1 45 1.5 6.3 <2 3.8 (1.7-8.2) •particle size <0.002 mm 29 Agric. Sei. Finl. 1 (1992) had to be concentrated by dry ashing at 450 °C. In 1989, all samples were ashed, and pressed into tabletsbefore measurement in cylindrical geometry (volume 30 cm3 ). Because the activities in grain and straw were close to the detection limits, the error of the measurement of l37Cs can be as big as 20-30 %. Results and discussion In 1987, 40K, 134Cs, 137Cs and small amounts of 106Ru and l25 Sb were detected in soil samples before the addition of sludge. The concentrations of l34Cs and l37 Cs in the soil are presented in Table 2. The largest amounts of radionuclides were detected at a depth of 20-40 cm in the clay soil in experiment 1 established in spring 1987. In spring 1986, the deposition had fallen on the surface of the field and in the autumn, when the field was ploughed, the active surface layer was turned down to about 20 cm. During the sampling the cores were cut at 20 cm and 40 cm. Therefore, the total amount of activity down to 40 cm was used for the calculation of transfer factors. The mean l37 Cs concentration in the soils (down to 40 cm) before the sludge treatment was 23 and 15 Bq kg"' dry weight in clay and 18 and 12 Bq kg"' dry weight in sandy loamand clay loam soil in experiments 1 and 2, respectively. The amount of l37 Cs per square meter (down to 40 cm) was calculated using the concentration of ,37Cs Bq kg"' dry weight and the volume weight (bulk density) of dry soil samples. In Finland the ratio of ,34Cs to l37 Cs in the Chernobyl fallout on 1 May, 1986 was 0.6 (Arvela et al. 1987). Using this ratio, the concentration of l34Cs and taking into account the radioactive decay the proportion of "old" fallout l37 Cs originating from nuclear weapons tests was estimated to be about 2000 Bq nr2 in the experimental soil. The Chernobyl ac- cident added 4000-7000 Bq nr2 of l37Cs to this soil. The addition of sludge still increased the amount of 137Cs by 10 000-12 000 Bq m 2 to a total of 16 000- 21 000 Bqnr 2 . The average dry matter yields of grain and straw are given in Tables 3 and 4. The addition of sludge didn't cause any statistically significant differences between the grain yields. The straw yields were in 1987significantly higher in thoseplots where sludge was added than in the plots without sludge addition. In 1988, the grain yields and especially the straw yields were remarkably lower than normal. This Table 3. The average dry matter yields of grain and straw in experiment 1 and differences between the treatments. Cereal/Soil Year Grain Straw kg ha ' kg ha' Differ- no Differ-no sludge sludge ence 1 sludge sludge ence 1 Spring wheat clay -87 2260 2190 2110 2130 2370 1990 2270 2300 NS NS NS NS 3280 4120 XX 1090 1100 NS-XX NS sandy loam -87 3850 4750 X -XX 1950 2040 NS Barley clay -87 2980 3270 2580 2150 3960 3660 3600 3520 NS X NS NS 2090 3110 XX 670 580 NS-XX NS sandy loam -87 2920 3790 XX 1960 1910 NS-XX NS ' Statistically significant differences in yields at the 0.05 level of significance are indicated by X at the 0.01 level of significance are indicated by XX NS = not significant 30 Agric. Sei. Finl. 1 (1992) was caused by the weather conditions during the growing season. The beginning of the summer was warmer and drier than normal. In July, there were many thundery rains and the precipitation was higher than normal (Ilmatieteen laitos 1988). Of the nuclides originating from the Chernobyl fallout, only l34Cs and l37 Cs were detected in the experimental plants. The concentrations of ,34Cs were so low that this isotope was detected mainly in 1987 and only in spring wheat and barley grown in the sludge treated plots. The mean concentrations of 137Cs and the range ofconcentrations in spring wheat and barley samples are given in Tables 5 and 6. In the sludge treated plots the mean concentrations of l37Cs in grain varied from 1 to 3 Bq kg"' dry weight in the first growing season and from 0.2 to 0.8 Bq kg"' in the second growing season. In the treatments without sludge addition the mean concentrations were 0.2- 0.3 Bq kg"' in 1987,0.1-0.4Bq kg"' in 1988 and 0.07- 0.08 Bq kg' in 1989. The average concentration of l37Cs in wheat in Finland was 0.05 Bq kg"' dry weight in 1985 (STUK 1987) and after the Chernobyl accident in 1986 it was 2.6 Bq kg"' (Rantavaara and Haukka 1987). In 1987 the average concentration of 137Cs in wheat was 0.4 Bq kg"' and in barley 0.6 Bq kg"' (Rantavaara 1991). The mean concentrations of l37 Cs in the grain of spring wheatand barley were about equal, or a little bit higher in spring wheat after sludge addition in the first experimental year. The mean concen- trations of l37 Cs in straw were higher in barley than in spring wheat. Application of sludge increased the concentration of 137Cs in grain 2-12 times and in straw 1-6 times as compared with crops grown in the control plots. The variations in different plots were high. The large variations in the activity concentrations were obviously due to the uneven distribution of radionuclides in the soil, to the heterogeneity of the sludge and the uneven spread of the sludge on the fields. In experiment 2 of the first growing season (in 1988) was the concentration of 137Cs in spring wheat and barley grown in plots to which sludge was added of the same magnitude as the concentration of 137Cs found in the first growing season (in 1987) in experiment 1 in the plots with the corresponding treatment. There wasn't any significant difference in the concentrations of 137Cs in grain whether the sludge was added in the previous autumn before ploughing or after ploughing in the spring before harrowing. Table 4The average dry matter yields of grain and straw in experiment 2 and differences betwwen the treatments. Cereal/Soil Year Grain Straw kg ha 1 kg ha' 1 no Differ- no Differ- sludge sludge ence 1 sludge sludge ence 1 Spring wheat clay -88 1620 1720 NS 790 900 NS -89 3530 3730 NS 1290 1500 NS sandy loam -88 1980 1990 NS 1110 1200 NS -89 3300 3330 NS 1450 1550 NS Barley clay -88 2200 2230 NS 640 560 NS -89 3730 4130 NS 1470 1710 NS sandy loam -88 2670 2930 NS 870 1060 NS -89 4010 4160 NS 1890 2190 NS 1 Statistically significant differences in yields at the 0.05 level of significance are indicated by X at the 0.01 level of significance are indicated by XX NS = not significant 31 Agric. Sei. Finl. 1 (1992) The main part of total activity is mostly translocated to the straw in the grain crop. Many earlier experiments have shown that the uptake in the straw is greater than in the grain (ohlen- schlaeger and Gissel-Nielsen 1989). The statistical comparison between the concen- tration of l37 Cs in grain and straw grown in soils fertilized with different way were used in analysis ofvariance and t-test. Results are given in Tables 5 and 6. In experiment 1 in 1987, the random variation of the concentration in spring wheat at different plots was so great that the analysis of variance did not show any significant difference (except on sandy loam). In experiment 2, the differences were statistically significant in both crops and both soil types in both experimental years. In the second experimental year the differences were statistically more significant on sandy soil both in grain and straw. The variations in the yields in different years did not show any significant effect on the concentrations of l37Cs in grain. The more significant effect was the variation in the concentration of l37Cs in soil and the time what l37 Cs has been in soil. The concentration ratio (CR) for radiocesium from soil (down to 40 cm) to grain was defined as Bq kg -1 grain per Bq kg" 1 soil (or soil and sludge). The mean CR values for l37Cs ranged between 0.02 and 0.07 in the first experimental year in both experiments on soils to which sludge was added. In the second experimental year the values ranged between 0.005 and 0.02. There was no statistically significant difference between CR values whether the sludge was added in the previous autumn before ploughing or after ploughing before harrowing in Table 5. The mean concentrations and the ranges of "7Cs (Bq kg 1 ) in grain and straw in experiment 1 (sludge applied in spring 1987) and differences between treatments. Cereal/Soil Year Grain Straw Bq kg-' Bq kg ' no Differ- no Differ- sludge sludge ence 1 sludge sludge ence 1 Spring wheat clay -87 0.37 2.2 NS 0.78 1.4 NS (0.24-0.56) (0.58-3,6) (0.5-1.1) (0.73-2.1) -88 0.14 0.26 NS 0,62 0.57 - 2 (0,098-0.19) (0.12-0.47) (0.44-0.65) sandy loam -87 0.34 2.9 X 0.67 3,9 NS (0.15-0.71) (1.4-5.3) (0,39-1.2) (1.9-7.8) -88 0.42 0.65 - 0.68 1.3 X (0.30-1.2) (0.59-0.85) (0.68-1.8) Barley clay -87 0.22 1.0 XX 0.9 3.9 XX (0.12-0.40) (0.79-1.1) (0.66-1.2) (3.4-4.8) -88 0.12 0.23 NS 0.59 1.0 (0-0.18) (0.15-0.37) (0.95-1.11) sandy loam -87 0.33 1.9 XX 1.2 5.7 XX (0.11-0.79) (1.1-2.4) (0.86-1.5) (4.5-6.7) -88 0.19 0.66 - 1.3 1.3 NS (0.53-1.04) (0.92-1.8) (0.81-1.7) 1 Statistically significant differences in concentrations at the 0.05 level of significance are indicated by X at the 0.01 level of significance are indicated by XX NS = not significant 2 the samples from four replicates are bulked 32 Agric. Sei. Finl. 1 (1992) the following spring. In soil to which no sludge was added the CR values were in 1987 (in the second year after the fallout from Chernobyl) 0.01-0.02, in 1988 0.006-0.03, in 1989 0.004-0.006. The results indicate that sludge has a significant influence on the concentration of radiocesium in grain crops only during the first year after sludge addition. For the sludge-treated soils varied the average transfer factor (TF) of l37Cs from soil to plant defined as Bq ha" 1 plant (grain and straw) per Bq ha" 1 soil (or soil and sludge) in first experimental years (1987 and 1988) from 24 x 10 "to 150 x 10"6 and in the second experimental year (1988 and 1989) from 5.6 x 10 6 to 52 x 10"6 and for the control soils from 10 x 10"6 to 58 x 10 6 and from 8.4 x 10"to 52 x 10 6 , respectively (see Table 7). In the first growing season there were distinct differences in transfer factors between the treatments where sludge was added and the treatments without sludge addition. In the second year, no differences were found in experiment 1. In experiment 2 there were differences in the TF factor also in the second growing season. The transfer factors were greater in those plots to which sludge was added. The fact that the sludge was over winter in soil did not change the plant availability of cesium in sludge in the first growing season after addition. In the following year the residual effect of the sludge was little. There were in the first year large variations in activities of plants between different replicates. These variations diminished during the second year. The differences between the plots treated with different way diminished also during the second year. However, in the experimental plots where sludge was added was also in the second year higher activities in plants than in the plots without Table 6. The mean concentrations and the ranges of ,37Cs (Bq kg 1) in grain and straw in experiment 2 (Sludge applied in au- tumn 1987) and differences between the treatments. Cereal/Soil Year Grain Straw Bq kg 1 Bq kg' 1 no Differ- no Differ- sludge sludge ence 1 sludge sludge ence 1 Spring wheal clay -88 0.16 1.0 XX 0.59 2.2 XX (0.12-0.20) (0.88-1.23) (0.44-0.77) (1.6-2.8) -89 0.080 0.29 X 0.32 0.59 X (0.053-0.10) (0.15-0.42) (0.27-0.36) (0.37-0.70) clay loam -88 0.19 2.4 XX 0.64 3.8 XX (0.18-0.22) (1.6-3.4) (0.48-0.77) (2.4-5.4) -89 0.079 0.44 XX 0.27 1.03 XX (0.057-0,094) (0.20-0.53) (0.19-0.32) (0.34-1.45) Barley clay -88 0.39 0.95 X 0.97 3.8 XX (0.13-0.81) (0.54-1.24) (0.86-1.10) (2.5-5.5) -89 0.079 0.31 X 0.36 0.94 NS (0.043-0.12) (0.20-0.46) (0.28-0.44) (0.34-1.45) clay loam -88 0.31 2.2 X 0.80 4.5 XX (0.083-0.84) (1.2-4.0) (0.50-1.10) (3.0-5.8) -89 0.068 0.81 XX 0.41 2.1 XX (0.051-0.11) (0.31-1.07) (0.31-0.53) (1.2-2.6) 1 Statistically significant differences in concentrations at the 0.05 level of significance are indicated by X at the 0.01 level of significance are indicated by XX NS = not significant 33 Agric. Sei. Finl. 1 (1992) sludge addition. After the sludge was added, the activities and CR and TF values were lower on clay soil than on sandy loam and clay loam soils, both in the first and second growing seasons. Clay soil fixes cesium added with sludge. Many inves- tigations have also shown that cesium migration and plant availability depend on the content and type of clay and on the organic matter and the potassium content of the soil. The transfer of l37Cs from soil to crop will decrease with increasing clay content and be higher from organic soils (Mascanzoni 1989, Haak 1990,Eriksson 1990). Table 7. The transfer factor (TF) of "7 Cs from soil to plant and differences between the treatment. Experiment 1 Soil/Cereal Sludge TF x 106 applica- 1987 1988 tion mean range Differ- mean range Differ- t D.M./ha ence 1 ence 1 Clay Spring wheat 0 35 (25-59) 3 9.4 22 46 (27-69)/ NS 5.6 (3.3-86) Barley 0 32 (24-37) 3 8.8 2 22 79 (63-110)/ XX 6.0 (4.7-6.8) Sandy loam Spring wheat 0 40 (32-52) x 28 22 120 (59-230)/ NS 20 (11-28) Barley 0 58 (23-110)-» 34 2 22 150 (100-190)/ X 24 (16-29) Experiment 2 Soil/Cereal Sludge TF x 106 applica- 1988 1989 tion mean range Differ- mean range Differ- t D.M./ha ence 1 ence 1 Clay Spring wheat 0 10 (6.7-13) 3 8,4 (7.7-9.2) t 22 24 (20-28)/ XX 17 (11-23) / X Barley 0 26 (11-49)3 13 (8.4-17) ■» 22 26 (16-34)/ NS 16 (9.0-21) / NS Clay loam Spring wheat 0 20 (15-26)3 13 (7.7-19) ■» 22 65 (39-100)/ X 17 (12-22) / NS Barley 0 21 (13-29)3 18 (8.8-35) ■» 22 74 (44-140)/ X 52 (31-59) / XX 1 Statistically significant differences in transfer factors at the 0.05 level of significance are indicated by X at the 0.01 level of significance are indicated by XX NS=not significant 2 The sample from four replicates are bulked 34 Agric. Sei. Finl. 1 (1992) References Arvela, H., Blomqvist, L., Lemmelä, H., Savolainen, A.- L. & Sarkkula, S. 1987. Environmental gamma radi- ation measurements in Finland and the influence of the meteorological conditions after the Chernobyl accident in 1986. STUK.-A65. Suppl. 10 to Ann. Rep. STUK- A55. Finnish Centre for Radiation and Nuclear Safety. 40 p. Eriksson, A. 1990. Adsorption and residence ofcesium in soils and organic matter. In: Deposition and transfer of radionuclides in nordic terrestric environment. NJF-ut- redning/rapport nr. 59: 3-12. Haak, E. 1990. Long term transfer of Cs and Sr to agricul- tural soils. In: Deposition and transfer ofradionuclides in nordic terrestric environment. NJF-utredning/rapport nr. 59: 28-39. Ilmatieteenlaitos - Meteorologiska institutet. 1988. Kuukau- sikatsaus Suomen ilmastoon. Yhteenveto 1988. 8 p. Lundström, Y. 1987. Personal communication with Y. Lundström. City of Helsinki, Water and Sewage Auth- ority. Mascanzoni, D. 1989. 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Radioactivity ofmilk, meat, cereals and other agricultural products in Finland after the Cher- nobyl accident in 1986. STUK-A5B. Suppl. 3 to Ann. Rep. STUK-A55. Finnish Centre for Radiation and Nuclear Safety. 105 p. Sippola, J. 1982. A comparison between a dry-combustion method and a rapid wet-combustion method for deter- mining soil organic carbon. Ann. Agric. Fenn. 21: 146- 148. Stuk, Finnish Centre for Radiation and Nuclear Safety. 1987. Foodstuffs other than milk. In:Studies on environ- mental radioactivity in Finland 1984-1985. Ann. Rep. STUK-54. p. 59-89. Tares, T. & Sippola, J. 1987. Changes in pH, in electrical conductivity and in the extractable amounts of mineral elements in soil, and the utilization and losses of the el- ements in some field experiments. Acta Agric. Scand. Suppl. 20:90-113. Toivanen, E. 1987. Personal communication with E. Toiva- nen. City of Helsinki, Water and Sewage Authority, Water Dep. May 1987. Vuorinen, J. & Mäkitie, O. 1955. The method of soil testing in use in Finland. Agrogeol. Publ. 63: 1-44. Ympäristöministeriö. 1991. Ohje 4. Puhdistamolietteen käyttö maanviljelyssä. (Användningen av slam från re- ningsverk inom jordbruket). 43 p. Manuscript received June 1991 Marketta Puhakainen Finnish Centre for Radiation and Nuclear Safety Box 268 SF-00101 Helsinki, Finland Toivo Yläranta Agricultural Research Centre of Finland Institute of Environmental Research SF-31600 Jokioinen,Finland 35 Agric. Sei. Finl. 1 (1992) SELOSTUS Viljelymaahan lisätyn kontaminoituneen jätevesilietteen vaikutus kevätvehnän ja ohran radionuklidi|)iloisii uksiin Marketta Puhakainen jaToivo Yläranta Säteilyturvakeskus ja Maatalouden tutkimuslaitos Kenttäkokein selvitettiin jätevesilietteen sisältämän radioak- tiivisen cesiumin siirtymistä kevätvehnään ja ohraan savi-, hieta- ja hiuesavimaasta. Kokeet tehtiin Jokioisissa Maata- louden tutkimuskeskuksessa. Osa kokeesta tehtiin levittä- mällä liete kynnettyyn peltoon keväällä 1987 ennen maan- muokkausta (koe 1), osa lietettä levitettiin syksyllä 1987 en- nen kyntöä (koe 2). Kokeet olivat kaksivuotisia. Käytetty liete oli Kyläsaaren puhdistamolla keväällä 1986 muodostunutta mädätettyä lietettä, joka sisälsi runsaasti Tshernobyl-laskeumasta peräisin olevia radionuklideja. Sen "7 Cs-pitoisuus oli 4700-5300 Bq/kg kuiva-ainetta. Liettees- sä oli mukana raakavedenpuhdistamolta peräisin olevaa Al- sulfaatilla saostettua sakkaa, jonkaradioaktiivisen cesiumin pitoisuus oli korkea. Lietettä levitettiin pellolle 20 tonnia kuiva-ainetta hehtaa- rille. Verranneruutuihin, joihin ei lisätty lietettä, lisättiin NPK-lannoitetta, niin että kasvien käytettävissä olevien ra- vinteiden määrät olivat likimain yhtä suuret kaikissa koeruu- duissa. " 7Cs:n siirtyminen maasta kasviin oli suurin niissä ruu- duissa, joihin lietettä oli lisätty. Jyvän '"Cs-pitoisuudet oli- vat 2-12 ja oljen 1-6kertaa suuremmat lietelisäyksen jälkeen kuin ilman sitä. Lietelisäyksen jälkeen savimaassa kasva- neen viljan pitoisuudet ja siirtokertoimet olivat pienemmät kuin hietamaassa kasvaneen. Savimaa pidätti hietamaata voimakkaammin lietteen mukana tulevaa cesiumia. Ensim- mäisenä satokautena siirtyi olkeen ja jyvään yhteensä 0.002 - 0.015 % maaperästä olevasta aktiivisuudesta, niissä ruu- duissa, joihin lietettä oli lisätty. Seuraavana satokautena määrä oli noin kolmasosa tästä, eli samaa suuruusluokkaa kuin ilman lietelisäystä olevilla pelloilla. Lietteen lisäystapa ei vaikuttanut '"Cs:n siirtymiseen maasta kasviin. Molem- missa kokeissa ensimmäisen koevuoden siirtokertoimet oli- vat samaa suuruusluokkaa riippumatta siitä, oliko liete lisät- ty keväällä 1987 vai syksynä 1987 seuraavaa kasvukautta varten. 36 Agric. Sei. Finl. 1 (1992)