[Soil sorption and transfer from it to plant of the radioactive and stable isotopes of chemical elements: methodology and experimental approach].

The adsorption of pair nuclides 60Co/Co and 65Zn/Zn by solid phase and their availability to plants were studied in soil suspension conditions and in the sod podzolic soil under controlled moisture. The situation when the radionuclide in constant activity is entered to system (surface water, soil) with different heavy metal contamination has been modeled. Was observed that soil contamination with heavy metal Co (Zn) significantly reduce sorption of the radionuclide 60Co (65Zn) by solid phase. As a result, the activity concentration of the 60Co or 65Zn in soil solution and, therefore, their mobility and potential availability to plants increases in 2-4 times with the total metal concentration increasing. The difference between two elements is that high Co concentration increase root uptake of the 60Co, whereas soil contamination with Zn reduce activity of 65Zn in the 14-days barley plants that may reflects diverse plant necessity of two elements and more important role of the isotopic exchange effect in the case of Zn.

Zinc as a marker in viscera of suspected metal phosphide poisoning: a study by neutron activation analysis.

Zinc as a marker element in the viscera of suspected metal phosphide poisoning has been studied during the present work. Neutron activation analysis (NAA) has been employed to detect and quantify the concentration of zinc in the viscera/stomach portion. The methodology has been developed on simulated and real life viscera samples to quantify the amount of zinc using NAA. The results obtained by NAA for real-life samples have been validated using a complementary analytical technique (viz. differential pulse anodic stripping voltammetry), and the values obtained were in good agreement, within +/- 5-8%. This exercise could be useful in medico-legal field for framing a definitive opinion about zinc phosphide poisoning.

Activity measurements and determination of gamma-ray emission intensities in the decay of 65Zn.

An International EUROMET exercise, Action 721, was organized with the objective of obtaining more reliable decay data on the disintegration of 65Zn. Nine laboratories participated, sending their results relating to activity measurements and 1115-keV gamma-ray emission intensity. Participants mainly used the 4pibeta-gamma coincidence method for the activity measurement, the resulting values and uncertainty budgets are described. New gamma-ray emission intensities were also measured in this exercise and, taking into account previously published values, the intensity of the 1115-keV gamma-ray emission has been determined to be 50.22(11)%.

The LSC efficiency for low-Z electron-capture nuclides.

In this paper, we apply the CIEMAT/NIST method to the three low-Z electron-capture nuclides 54Mn, 55Fe and 65Zn by using the KLM and KL1L2L3M atomic rearrangement models, respectively. The counting efficiencies are computed with the new code EMILIA, which comprises an improved model for the interaction of low-energy X-rays with the scintillation cocktail. The calculated counting efficiencies are compared with experimental results.

Standardization and nuclear decay data of 65Zn.

Standardization by means of 4pibeta-gamma coincidence counting was applied to calibrate a 65Zn solution within the scope of EUROMET project no. 721. The activity result was combined with gamma-ray spectrometry measurements to investigate the photon emission probabilities. The half-life of 65Zn was measured with improved accuracy by means of 4pi ionization chamber measuring systems that were also used for secondary activity determination. In addition, we tested a new secondary standardization procedure by means of liquid scintillation counting.

An approach based on the SIR measurement model for determining the ionization chamber efficiency curves, and a study of 65Zn and 201Tl photon emission intensities.

The measurement model used to determine ionization chamber efficiency curves accounts from the outset for impurity corrections and beta spectrum shapes. The curves are represented by exponentials of polynomials whose coefficients are adjusted using non-linear least-squares minimization. The curves are validated by comparing with SIR key comparison reference values (KCRVs) and other published curves. The associated covariance matrix is also evaluated. Deviations from model predictions for 65Zn and 201Tl using recommended nuclear data are studied.

Absolute activity measurement of the electron-capture-based radionuclides 139Ce, 125I, 192Ir and 65Zn by liquid scintillation coincidence counting.

Four radionuclides with electron-capture-based decay schemes have been directly measured by a liquid scintillation coincidence extrapolation technique. 125I, 192Ir and 65Zn were measured as part of international key comparisons held under the auspices of the International Bureau of Weights and Measures (BIPM). The 139Ce measurements formed part of a regional comparison organized by the Asia Pacific Metrology Programme (APMP). Since 139Ce decays purely by electron-capture, the basic method is described for this radionuclide. Results and difficulties encountered are discussed and uncertainty budgets are presented.

Standardisation of 54Mn and 65Zn using a software coincidence counting system.

The activities of 54Mn and 65Zn have been determined by 4pi(PC)-gamma coincidence counting, with efficiency variation performed by the conventional method of altering the self-absorption in the sources as well as by the computer discrimination method. The standardisation of 65Zn presents some complications requiring optimisation of the gamma-ray energy window settings to achieve a linear efficiency-extrapolation curve. Determination of these optimal settings by the conventional coincidence method is a tedious task. These difficulties have been reduced by the utilisation of a software coincidence counting system that records time and amplitude information of individual pulses from coincidence measurements, where the coincidence parameters are set after the data collection process has completed, facilitating multiple data evaluations on a single data set. The optimal gamma-ray energy window settings for the 65Zn standardisation were derived from the results of the 54Mn standardisation, as well as from studies of the 65Zn data itself. The setting of the PC channel thresholds for K and both (K+L) electrons is also discussed. The results are compared with those attained using conventional coincidence counting.

Precise Zn isotopic ratio measurements of human red blood cell and hair samples by multiple collector-ICP-mass spectrometry.

Precise 66Zn/64Zn and 68Zn/64Zn isotopic ratios of biochemical samples have been measured using multiple collector-ICP-mass spectrometry (MC-ICPMS). In order to eliminate the mass spectrometric interferences on Zn isotopes (e.g., 64Ni+ and 136Ba2+), we chemically purified the analyte using an ion chromatographic technique. The resulting precisions of the 66Zn/64Zn and 68Zn/64Zn ratio measurements were 0.05/1000 and 0.10/1000 (2SD), respectively, which were enough to detect the isotopic variation of Zn in nature. Red blood cell (RBC) samples were collected from five volunteers (four males and one female), including a series of 12 RBC samples from one person through monthly-based sampling over a year. These were analyzed to test possible seasonal changes and variations in 66Zn/64Zn and 68Zn/64Zn ratios among the individuals. The 66Zn/64Zn and 68Zn/64Zn ratios for a series of 12 RBC samples collected over a year were 0.43/1000 and 0.83/1000 higher than the values of highly purified Zn metal (JMC Zn), and no seasonal change could be found. The 66Zn/64Zn and 68Zn/64Zn ratios for RBC samples collected from five volunteers did not vary significantly. In order to investigate Zn isotopic heterogeneity in a human body, Zn isotopic ratios of a hair sample collected from one of the volunteers was also analyzed. The 66Zn/64Zn and 68Zn/64Zn ratios for the hair sample were 0.59/1000 and 1.14/1000 lower than the mean value of RBC samples. This result demonstrates that detectable isotopic fractionation occurs in the human body. The data obtained here suggest that the isotopic ratios of trace metals could provide new information about transportation of metal elements in vivo.

A new, simple and precise method for measuring cyclotron proton beam energies using the activity vs. depth profile of zinc-65 in a thick target of stacked copper foils.

The proton beam energy of an isochronous 18MeV cyclotron was determined using a novel version of the stacked copper-foils technique. This simple method used stacked foils of natural copper forming 'thick' targets to produce Zn radioisotopes by the well-documented (p,x) monitor-reactions. Primary beam energy was calculated using the (65)Zn activity vs. depth profile in the target, with the results obtained using (62)Zn and (63)Zn (as comparators) in close agreement. Results from separate measurements using foil thicknesses of 100, 75, 50 or 25µm to form the stacks also concurred closely. Energy was determined by iterative least-squares comparison of the normalized measured activity profile in a target-stack with the equivalent calculated normalized profile, using 'energy' as the regression variable. The technique exploits the uniqueness of the shape of the activity vs. depth profile of the monitor isotope in the target stack for a specified incident energy. The energy using (65)Zn activity profiles and 50-µm foils alone was 18.03±0.02 [SD] MeV (95%CI=17.98-18.08), and 18.06±0.12MeV (95%CI=18.02-18.10; NS) when combining results from all isotopes and foil thicknesses. When the beam energy was re-measured using (65)Zn and 50-µm foils only, following a major upgrade of the ion sources and nonmagnetic beam controls the results were 18.11±0.05MeV (95%CI=18.00-18.23; NS compared with 'before'). Since measurement of only one Zn monitor isotope is required to determine the normalized activity profile this indirect yet precise technique does not require a direct beam-current measurement or a gamma-spectroscopy efficiency calibrated with standard sources, though a characteristic photopeak must be identified. It has some advantages over published methods using the ratio of cross sections of monitor reactions, including the ability to determine energies across a broader range and without need for customized beam degraders.

Interactions between metals in rat jejunum: implications on the nature of cadmium uptake.

Cadmium uptake from the lumen of the rat jejunum is characterized by apparent saturability and by sensitivity to inhibition by Zn and Ca. A variety of other heavy metals also inhibit intestinal Cd transport. The hypothesis was tested that Cd competes with other metals for their transport systems. The observed discrepancy between the apparent Ki and Km values for interaction between Cd and Zn argues against competition. Further, inhibition of Cd uptake by Zn, Ca and La is independent of Cd concentration over the range in which the system approaches partial apparent saturation (5-100 microM). Relatively high concentrations of other polyvalent cations, including Cd itself and Pb, Ni, Cr3+, Sr, Mg and polylysine, also depress 109Cd uptake. The possibility is suggested that these cations non-specifically neutralize membrane charges, and thus interfere with membrane binding and subsequent internalization of 109Cd. This explanation obviates the need for the unlikely assumption that specific membrane carriers exist to facilitate uptake of a toxic and non-essential metal like Cd.

Age-dependent variation of zinc-65 metabolism in LACA mice.

Mice were gavaged with zinc-65 solution, 8.6-19.3 kBq per mouse, and the whole-body retention and organ content of zinc-65 were measured at different times after administration. The age-dependence of the fractional absorption of zinc-65 from the gastrointestinal tract (f1), the endogenous faecal excretion fraction of zinc-65 (EFEF), tissue distribution and whole-body retention were determined. The f1 values obtained were 0.86 +/- 0.15, 0.64 +/- 0.11, 0.52 +/- 0.07 and 0.39 +/- 0.02 in suckling, adolescent, young adult and older mice, respectively. The EFEF values determined were 0.083 +/- 0.008, 0.099 +/- 0.004, 0.122 +/- 0.018 and 0.144 +/- 0.005 of intraperitoneally injected zinc-65 in suckling, adolescent, young adult and older mice at administration. Zinc-65 mainly distributed in the liver, muscle, lung, kidneys and bone. In some tissues, there was an inverse relationship between the relative content of gavaged zinc-65 and the animal's age at administration. The whole-body biological half-lives of zinc-65 increased with animal age. The influence of the age-dependent variation of zinc-65 metabolism on internal dose and on radiation protection is discussed.

Multitracer studies on the accumulation of radionuclides in mushrooms.

We used the multitracer technique to study the transfer of several radionuclides to two mushroom species. Radionuclides accumulated in the fruiting bodies of the mushrooms in the order of 83Rb > 65Zn > 54Mn > 22Na > 75Se and 85Sr > 60Co > 88Y, 102Rh, 139Ce, 143.144Pm, 146.153Gd and 173Lu > 175Hf. The concentration ratio values for 83Rb, 65Zn and 54Mn in the fruiting bodies were more than 10, whereas those for 60Co, 88Y, 102Rh, 121mTe, 175Hf and the rare earth elements were less than 1. There were major differences in the accumulations of the alkali elements.

Remobilisation of 109Cd, 65Zn and 54Mn from freshwater-labelled river sediments when mixed with seawater.

A major fraction of trace metals transported by rivers is associated with sediments, especially during flooding, when erosion and resuspension increase sediment loads. Upon contact with seawater in estuaries, changes in ionic strength and pH may remobilise trace metals from sediment surfaces into more bioavailable forms. The objective of the present work was to investigate time-dependent interactions between trace metals and freshwater sediments and their potential remobilisation upon contact with seawater. Two river sediments (one organic and one inorganic) were labelled with 109Cd2+, 65Zn2+ and 54Mn2+ radioactive tracers for periods up to 6 months. Sorption of tracers occurred rapidly (> or = 80% sorption, < 1 h), followed by a slower approach to pseudoequilibrium. Kd(6 months) were estimated as 460, 480 and 2200 ml/g (inorganic sediment) compared to 5300, 4000 and 1200 ml/g (organic sediment) for 109Cd, 65Zn and 54Mn, respectively. Remobilisation of tracers from labelled sediments was studied using sequential extractions. Artificial seawater extracts simulated an estuarine environment. Subsequent extractions provided information about more strongly sorbed tracer fractions within sediments. Remobilisation of 109Cd by seawater was significant (> 65%) and least affected by sediment type or freshwater labelling time. Redistribution of Cd to strongly bound phases was minimal (4% and 1% of 109Cd in strongly oxidisable fractions). Seawater remobilisation of 65Zn was significantly greater from the organic sediment (54%) compared to the inorganic sediment (8%), where a large fraction of 65Zn (14%) became irreversibly bound. Similarly, more 54Mn was remobilised by seawater from the organic sediment than the inorganic sediment (66% and 3% remobilised, respectively), i.e., 54Mn became more strongly bound in the inorganic sediment. A simple three-box model, based on first-order differential equations, was used to describe the interaction between tracers in spiked freshwater and two operationally defined sediment fractions ("seawater exchangeable" and "seawater unexchangeable") up to 6 months of freshwater labelling. Model simulations were fitted to experiment data and apparent rate constants were calculated using numerical optimisation methods. Sorption ratios from modelling data (i.e., k1/k2) were greater for organic compared to inorganic sediments, while fixation ratios were higher in inorganic sediments. In conclusion, trace metals can be remobilised from sediments on contact with seawater in estuaries. High organic content in sediments increased initial sorption of tracers but inhibited redistribution to more strongly bound fractions over time, resulting in greater remobilisation of tracers when in contact with seawater.

Tissue distribution of polaprezinc in rats determined by the double tracer method.

The tissue distribution of polaprezinc (an insoluble zinc complex of L-carnosine) in rats was studied by the double tracer method using [U-14C-histidine]-, 65Zn-polaprezinc. The 65Zn-radioactivity was measured with an auto-gamma counter, and the 14C containing 65Zn was converted to an absolute count according to the calibration curve for quenching with a liquid scintillation counter with the spill-over method. After the administration of 14C-, 65Zn-polaprezinc to rats, the excretion ratio and time courses in the tissues of the 14C-and 65Zn-radioactivity were different each other. We found that polaprezinc was metabolized as endogenous amino acid or zinc after dissociation in the body. The zinc concentration in plasma reached its maximum at 1 h and decreased slowly, returning to the endogenous level at 11 h after the administration of non-labeled polaprezinc. The concentrations of zinc in liver, kidney, testis, prostate, and cerebrum remained rather constant. The replacement ratios of 65Zn to zinc in the tissues at its maximum percentage were 40% in plasma, 16-20% in liver, kidney, blood, and prostate. The low replacement ratios in testis and cerebrum (2-3%) suggested that zinc uptakes in testis and brain were regulated by the blood-testis-barrier and blood-brain-barrier, respectively.

Reconstruction of radioactive contamination in the Columbia River.

As part of the Hanford Environmental Dose Reconstruction Project, an unsteady flow hydraulic model, modified to include radionuclide decay, was used to simulate the transport of radionuclides released to the Columbia River from Hanford. The model was applied to the river from Priest Rapids Dam to the vicinity of Portland, Oregon, for the period from January 1950 through January 1971. Model output consisted of monthly-average water concentrations for 24Na, 32P, 65Zn, 76As, and 239Np. Model validation was accomplished by comparing computed water depths and 51Cr concentrations to measured field data. This paper discusses the modeling approach and compares the results to historical river monitoring data collected during the peak years of operation.

Predicting the radionuclide fraction transferred to consumption through grain foods.

Data on the root uptake by wheat of three activation products, 54Mn, 65Zn and 63Ni, and two fission products, 90Sr and 137Cs, were obtained in a long-term field study. Soil-plant transfer factors calculated from these data were used to determine the amount of various radionuclides that may reach the humans through grain foods. The temporal variation of this contribution showed that the fraction of 54Mn and 65Zn transferred to human consumption during the first year was considerable, but owing to decay and decreasing uptake the gradients diminished and the accumulated fraction flattened to a plateau. In contrast, the fractions of the long-lived 63Ni, 90Sr and 137Cs transferred to human consumption were smaller and with nearly constant gradients. This study shows that the long-lived radionuclides are transferred to the same extent as 54Mn and 65Zn. In the long-term, the greatest doses from grain products are contributed by the long-lived radionuclides.

Protracted exposure to fallout: the Rongelap and Utirik experience.

From June 1946 to August 1958, the U.S. Department of Defense and the U.S. Atomic Energy Commission (AEC) conducted nuclear weapons tests in the Northern Marshall Islands. On 1 March 1954, BRAVO, an above-ground test in the Castle series, produced high levels of radioactive material, some of which subsequently fell on Rongelap and Utirik Atolls due to an unexpected wind shift. On 3 March 1954, the inhabitants of these atolls were moved out of the affected area. They later returned to Utirik in June 1954 and to Rongelap in June 1957. Comprehensive environmental and personnel radiological monitoring programs were initiated in the mid 1950s by Brookhaven National Laboratory to ensure that body burdens of the exposed Marshallese subjects remained within AEC guidelines. Their body-burden histories and calculated activity ingestion rate patterns post-return are presented along with estimates of internal committed effective dose equivalents. External exposure data are also included. In addition, relationships between body burden or urine-activity concentration and declining continuous intake were developed. The implications of these studies are: (1) the dietary intake of 137Cs was a major component contributing to the committed effective dose equivalent for the years after the initial contamination of the atolls; (2) for persons whose diet included fish, 65Zn was a major component of committed effective dose equivalent during the first years post-return; (3) a decline in the daily activity ingestion rate greater than that resulting from radioactive decay of the source was estimated for 137Cs, 65Zn, 90Sr and 60Co; (4) the relative impact of each nuclide on the estimate of committed effective dose equivalent was dependent upon the time interval between initial contamination and rehabilitation; and (5) the internal committed effective dose equivalent exceeded the external dose equivalent by a factor of 1.1 at Utirik and 1.5 at Rongelap during the rehabitation period. Few reliable 239Pu measurements on human excreta were made. An analysis of the tentative data leads to the conclusion that a reliable estimate of committed effective dose equivalent requires further research.

Standardization of 65Zn by 4piPC-gamma coincidence counting method with efficiency extrapolation.

A 65Zn solution was standardized by the 4piPC-gamma efficiency-extrapolation coincidence counting method. Theoretical aspects of coincidence equations, efficiency equations and linearity conditions are reviewed. Experimental measurements were performed for two low level discrimination thresholds for the PC channel (counting K+L or K X-rays or Auger electrons from EC decay) and for three different settings of the gamma window. Requirements on gamma channel set-up for linear extrapolation were established by using a Pb absorber or by proper gamma window setting. The measured activity values were discussed and found in good agreement with those obtained with a calibrated ionization chamber.

Experimental verification of the half-life of 65Zn.

The half-life of 65Zn was determined experimentally and compared with literature values. Two ampoules of a 65Zn solution were measured at regular intervals in two ionisation chambers over a period corresponding to nearly two half-lives. The result of 243.8+/-0.3 days is in agreement with the value of 244.0+/-0.2 days obtained by De Roost et al. (Z. Phys. 250 (1975) 395) at the same institute (previously called CBNM) in 1972. Moreover, this half-life is supported by most of the other measurements reported in the literature.