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Biomedical subjects

K Bunzl

Publications and source records attributed to K Bunzl.

At least 37 records · Page 2Linked to original sources
PubMed1996

Association of fallout radiocesium with soil constituents: effect of sterilization of forest soils by fumigation with chloroform.

The effect of soil sterilization by chloroform fumigation on the release of fallout radiocesium incorporated in the fungal biomass of the organic layer of two forest soils was investigated by applying a sequential extraction procedure for radiocesium. The amount of the biomass in all soil samples was estimated by determination of the dissolved organic carbon (DOC) before and after fumigation, and qualitatively also by the ergosterol test. The five fractions obtained by sequential extraction (modified Tessier procedure) were: (I) easily exchangeable, (II) bound to oxides, (III) bound to organic matter, (IV) persistently bound, (V) residual. For the samples from the soil under spruce trees, no significant effects were apparent in any of these five fractions as a result of chloroform fumigation, indicating that the amount of radiocesium in the biomass of this soil was obviously negligibly small compared with the radiocesium associated with other soil constituents. The results obtained for the soil samples from the beech stand, however, reveal that the destruction of the biomass by chloroform fumigation modified considerably the extent of the association (i.e., binding) of radiocesium with the various other soil constituents (especially the clay minerals). As a result of this rapid redistribution of radiocesium released by the fungal biomass, it is not possible, in general, to attribute the observed increase of radiocesium in fraction I (easily exchangeable) after soil sterilization quantitatively to radiocesium released by the biomass. A reliable method to determine the amount of radiocesium incorporated in the fungal biomass of the soil samples which also contain clay minerals has, therefore, still to be developed.

Biomass↗
PubMed1996

In situ gamma-spectrometry several years after deposition of radiocesium. Part I. Approximation of depth distributions by the Lorentz function.

Several years after the deposition of fallout-radiocesium, the maximal activity of this radionuclide will not remain at the soil surface but be found rather in deeper layers. In order to estimate the total radiocesium contamination of a large area and the resulting gamma-dose rate by in-situ spectrometry, it is necessary to approximate the vertical distribution of this radionuclide by an analytical function. Observations at ten undisturbed grassland soils and Bavaria, Germany, show that the resulting depth distributions can be approximated closely by a three-parameter Lorentz function. This function characterises the observed distributions in all three critical sections, i.e. the surface layer, the distribution around the maximal concentration, and the tail at greater depth. It is also shown that the observed total activity per unit area of the soil due to 137Cs agrees very well with the corresponding value obtained from the integrated Lorentz function. The two coefficients of the Lorentz function, which characterise the location (depth) and width of the maximum in the activity distribution, are shown to be correlated. In part II of this study, it will be shown how the parameters of the Lorentz function can also be obtained by in-situ gamma-ray spectrometry. As a result, it is possible to use in-situ gamma-ray spectrometry to obtain the total 137Cs activity per unit area also for sites where the vertical distribution of this radionuclide in the soil is no longer exponential.

Cesium Radioisotopes↗
PubMed1995

Residence times of global weapons testing fallout 237Np in a grassland soil compared to 239 + 240Pu, 241Am, and 137Cs.

The vertical distribution of weapons testing fallout 237Np has been determined in an undisturbed grassland soil (Alfisol). By using a compartmental model for multi-layered soils, the mean residence half-times of 237Np in each soil layer were calculated and compared with results on weapons fallout 239 + 240Pu, 241Am and 137Cs in the same soil. The results show that the mobility of 237Np was in most soil horizons either equal or slightly enhanced as compared to that of Pu, Am, and radiocesium.

Americium↗
PubMed1993

Deposition of radiocesium to the soil by stemflow, throughfall and leaf-fall from beech trees.

The amount of Chernobyl-derived 137Cs transferred to the soil by stemflow, throughfall (precipitation under the tree crown), and leaf-fall from three beeches was investigated as a function of time in the growing seasons of 1991 and 1992. Up to 70 Bq/week was deposited with the stemflow, mainly in dissolved form (< 0.45 micron) rather than in particulate form (> 0.45 micron). The ratio of dissolved radiocesium to particulate radiocesium was about 10 in the stemflow. It varied considerably with time, but since these variations followed the same pattern for all three trees, they indicated a common cause to be responsible for the fractionation of radiocesium (e.g. meterological conditions for bark weathering). A significant correlation was observed for the amount of dissolved 137Cs (in Bq) and the amount of stemflow (in liters). The 137Cs concentration in the stemflow (in Bq/1), however, decreased with increasing stemflow intensity (in Bq/week). For particulate radiocesium such correlations were not detected. Up to 5 Bq/m2 per week was deposited with the throughfall from the canopy, mainly in particulate form (ratio dissolved radiocesium to particulate radiocesium = 0.34). The mean total annual amounts of 137Cs deposited to the ground (dissolved+particulate) for the three trees were: stemflow: 1991 600 Bq; 1992 460 Bq; throughfall: 1991 and 1992 approximately 100 Bq/m2 each; leaffall: 1992 approximately 10 Bq/m2. The data indicate that at present a substantial amount of the radiocesium in the leaves derives already from root uptake.

Accidents↗
PubMed1992

Migration of radiocesium in two forest soils as obtained from field and column investigations.

Depth profiles of radiocesium were measured in a podsolic parabrown earth of a spruce stand and in a podsol of a pine stand up to 3 years after the Chernobyl accident. At the same sites undisturbed soil columns of 20 cm diameter and 40 cm length were taken, transferred to the laboratory and irrigated intermittently with synthetic rainwater containing initially a known amount of radiocesium. The resulting migration of radiocesium in the columns under unsaturated conditions was determined as a function of time up to 3 years with a scanner technique. The depth profiles of radiocesium observed in the field and in the columns were evaluated with a compartment model to obtain the residence half-times of this radionuclide in the various soil horizons. The field observations yielded a residence half-time in the organic layer of both soils of approximately 4-6 years for Chernobyl-derived cesium, and of 10-15 years for cesium from the global fallout of weapons testing. In the mineral soil (0-5 cm), under spruce the residence time of Chernobyl-derived cesium was 15 years, that of cesium from the global fallout (present in the soil since approximately 30 years) was 50 years. Under pine, the residence time in the mineral soil was 4 years for Chernobyl-derived cesium and 11 years for global fallout cesium. Obviously, in each layer of both soils cesium becomes less available for migration with time. The residence times of radiocesium evaluated from the column experiments were in good agreement with those obtained from the field observations. Due to the comparatively short duration of the column experiments, however, the long-term increase of the residence time of radiocesium in the soil was not yet unambiguously observable.

Accidents↗
PubMed1992

Vertical migration of plutonium-239 + -240, americium-241 and caesium-137 fallout in a forest soil under spruce.

The vertical activity distributions of fallout 238Pu, 239+240Pu, 241Am, 134Cs and 137Cs in a forest soil (Hapludult) were determined at several locations in a spruce stand separately according to their origin (global fallout or Chernobyl fallout). To determine the rate of migration of these radionuclides in each soil horizon, the observed depth profiles of the radionuclides were evaluated with a compartment model. In the top organic horizons (LOf1 and Of2), the migration rates for all radionuclides from both sources were above 0.5 cm per year. In the Oh horizon the migration rates observed for global fallout Pu, Am and Cs were similar (0.2-0.4 cm per year). Compared with Pu, however, the mobility of Am is slightly, but statistically significantly, enhanced. The highest rate in this layer was found for Chernobyl-derived radiocaesium (2 cm per year). In the layers of the mineral horizon (depth 0-2, 2-5 and 5-10 cm) the observed migration rates were very similar for global fallout Pu (0.08-0.7 cm per year) and Am (0.1-2 cm per year). In comparison, the migration rate of global fallout radiocaesium was about half in each layer. The highest rate was observed again for Chernobyl-derived radiocaesium (0.5-3 cm per year).

Accidents↗
PubMed1989

[The transfer of 137Cs and 90Sr into flour, bran and straw from wheat, rye, barley and oats in the years 1982, 1986 (reactor accident in Chernobyl) and 1987 in field studies].

The specific activity of 137Cs and 90Sr from the global fallout, as well as from the fallout after the reactor accident at Chernobyl, was determined in flour, bran and straw from wheat, rye, barley and oats as well in the corresponding soils (Cambisol). The results show that the activity of 137Cs, but not of 90Sr, in the plant material was considerably higher in 1986, and still to some extent in 1987, compared to 1982. For 137Cs an 90Sr, as well as for most cereal samples, the activity in the bran and straw was significantly higher than in the flour. Determination of stable potassium and calcium in all samples revealed that this enrichment is, to a large extent, the result of a comparable enrichment of these elements in brans and straw. The plant/soil concentration ratios, averaged over all cereals, were for 137Cs (1982 and 1987): flour 0.026 +/- 0.018; bran 0.079 +/- 0.042; straw 0.055 +/- 0.027. For 90Sr (1982, 1986, and 1987): flour 0.19 +/- 0.095; bran 0.70 +/- 0.23; straw 2.35 +/- 0.82.

Accidents↗
PubMed1989

Interception and retention of Chernobyl-derived 134Cs, 137Cs and 106Ru in a spruce stand.

The time dependence of the specific activity of Chernobyl-derived 134Cs, 137Cs and 106Ru was determined in vegetation and soil samples from an old spruce stand within a period of 600 days after the beginning of the radioactive fallout. The results show that 70% of the total activity of radiocesium and 60% of radioruthenium deposited in the spruce stand were retained initially in the canopy. They were removed from the needles and twigs as a result of weathering (rain, wind, litter fall) and transferred to the forest floor, but only rather slowly (half-lives in the canopy: radiocesium, 90 days for the period 0-130 days, 230 days for the period 130-600 days; radioruthenium, 95 days for the period 0-200 days). The transfer of radiocesium and ruthenium to the forest floor by litter-fall was small when compared with that of weathering by rain or wind (radiocesium 7%, radioruthenium 8%, with respect to the total activity deposited in the canopy). The total deposition of radiocesium and ruthenium in the spruce stand was higher by 20 and 24%, respectively, than that observed in nearby grassland. The deposition velocity of radiocesium in the spruce stand was estimated at 5.5 mm s-1, higher by a factor of 10 than the figure for grassland. Similar values were found for radioruthenium.

Accidents↗
PubMed1989

Seasonal variation of soil-to-plant transfer of K and fallout 134,137Cs in peatland vegetation.

For three plants from a peat bog (Trichophorum caespitosum, Molinia coerulea, Calluna vulgaris) the concentration of 137Cs, the ratio 137Cs:134Cs, and stable K was determined in intervals of about 14 d from June to November 1987. The results show that for two grasses, Trichophorum caespitosum and Molinia coerulea (which have only perennial roots but sprout every year while the old leaves wither), the concentration of 137Cs decreased considerably during the growing season (1800-240, respectively, 4000-320 Bq kg-1 dry weight). A remarkably similar behavior was observed for the seasonal variability of K and radiocesium in the two grass species, which resulted in a nearly constant ratio of 137Cs:K during the year. In contrast, for the evergreen plant Calluna vulgaris (heather) which was contaminated surficially by the Chernobyl fallout, the concentrations of K and 137Cs were rather constant during 1987 (leaves about 10,000; stems about 5000 Bq kg-1 dry weight), even though radiocesium was taken up by the leaves and transported within the plant. For the two grasses, the plant:soil concentration ratios (CR) were obtained separately for total 137Cs, 137Cs from the global fallout, and Chernobyl-derived 137Cs. The CR of 137Cs from the global fallout decreased for Trichophorum caespitosum from 1.9 in the spring to 0.08 in the autumn, and for Chernobyl-derived 137Cs from 1.4 to 0.2. For Molinia coerulea, a similar behavior was observed. Possible reasons for the seasonal variability of the CR values and the different behavior of 137Cs from the global fallout and from the Chernobyl debris are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Cesium Radioisotopes↗
PubMed1988

Effect of microbial biomass reduction by gamma-irradiation on the sorption of 137Cs, 85Sr, 139Ce, 57Co, 109Cd, 65Zn, 103Ru, 95mTc, I by soils.

Six soils, two Sphagnum peat samples and a clay mineral were irradiated with 40 and 80 kGy (4 and 8 Mrad) from a 60Co source. As a result the microbial biomass, determined separately for each sample, decreased considerably. Depending on the radionuclide, the sorption, as characterised by the distribution coefficient, decreased, increased or remained unchanged. The effect of the irradiation on the sorption of the radionuclides depended, in general, also on the type of the sample, especially whether well humified soils, (e.g. crop soils), poorly humified samples (Sphagnum peat, O-horizon from woodland), or a clay mineral was employed. The data reveal that irradiation produces, besides sterilization, also other effects in soils, which can change their sorption properties.

Adsorption↗
PubMed1987

Soil to plant transfer of 239 + 240Pu, 238Pu, 241Am, 137Cs and 90Sr from global fallout in flour and bran from wheat, rye, barley and oats, as obtained by field measurements.

Crops of wheat, rye, barley and oats were grown on fields where the contamination of the soil with radionuclides resulted exclusively from global fallout debris. After machine harvesting and milling, the concentrations of 239 + 240Pu, 241Am, 137Cs and 90Sr were determined separately in bran and flour, as well as in the soils. The concentrations of 239 + 240Pu in wheat, rye and barley flour were between 59 and 180 microBq kg-1, and in oat flour 1100 microBq kg-1. The range of concentrations of the other radionuclides for the four flours were: 241Am, 5-70 microBq kg-1, 137Cs, 260-380 mBq kg-1; 90Sr, 310-1300 mBq kg-1. The corresponding concentrations of the radionuclides were always considerably higher in the bran than in the flour, with the exception of oats. The range of this factor depends on the cereal: for 239 + 240Pu, 19-25; 241Am, 10-38; 137Cs, 4-6; and for 90Sr, 4-7. Similar differences between flour and bran were observed for stable elements, for example K, Ca and Fe. The soil-to-plant transfer factors of 239 + 240Pu for wheat, rye and barley flour were between 0.00026 and 0.00078 (oats 0.017) and for bran between 0.0048 and 0.02 (oats 0.014). For 241Am the corresponding values were somewhat lower. For the wheat, rye and barley flour the transfer factors of 137Cs were between 0.013 and 0.018 (oats 0.069) and, for the bran, between 0.08 and 0.10 (oats 0.16). The corresponding values for 90Sr were significantly higher: for flour between 0.08 and 0.14 (oats 1.2) and for bran between 0.62 and 0.93 (oats 1.5).

Americium↗
PubMed1983

Fallout 239/240Pu and 238Pu in human tissues from the Federal Republic of Germany.

To determine the present level of plutonium in human tissues of people in the F.R.G., due solely to fallout from weapons testing, 30 sets of tissues and bones from Munich residents were obtained at autopsy. Each set of tissues consisted of the entire lung, the entire liver, 300 g vertebrae, 300 g ribs and the lymph nodes. All subjects were males, born before 1940. Wet ashing, followed by solvent extraction, electrodeposition, and alpha-spectrometry were used to isolate and quantitate the plutonium isotopes present. The median concentrations of 239/240Pu (in fCi/kg wet weight) observed were: livers (530), vertebrae (92), ribs (73), lymph nodes (58) and lungs (28). The ratio of 238Pu/239/240Pu (in %) was livers 3.5, lungs 5.6, ribs 4.0 and vertebrae 3.2. Age trends for the plutonium concentration in livers, lungs, vertebrae and ribs were not observable. Possible correlations between the plutonium concentrations in livers, lungs and bones are discussed. The results are in many respects similar to observations in the U.S.A. and Southern Finland.

Adult↗