Yukio Katayama

Residual radioactivity in the soil of the Semipalatinsk Nuclear Test Site in the former USSR.

This paper deals with our efforts to survey residual radioactivity in the soil sampled at the Semipalatinsk Nuclear Test Site and at off-site areas in Kazakhstan. The soil was sampled at the hypocenter where the first Soviet nuclear explosion was carried out on 29 August 1949, and at the bank of the crater called Bolapan, which was formed by an underground nuclear detonation on 15 January 1965 along the Shagan River. As a comparison, other soil was also sampled in the cities of Kurchatov and Almaty. These data have allowed a preliminary evaluation of the contemporary radioactive contamination of the land in and around the test site. At the first nuclear explosion site and at Bolapan, higher than background levels of 239,240Pu with weapons-grade plutonium were detected together with fission and activation products such as 137Cs, 60Co, 152Eu, and 154Eu.

Radial movement of sapwood-injected rubidium into heartwood of Japanese cedar (Cryptomeria japonica) in the growing period

Rubidium solution was injected in the sapwood of a Japanese cedar cultivar in the growing period, and its radial movement in stem was traced to investigate the accumulation of alkali metals in the heartwood. Sapwood-injected Rb was detected in outer heartwood at 10xa0days after the treatment, and continued increasing at 20xa0days after. Radial movement of Rb toward heartwood was considered to occur soon after the treatment, and to decline at a certain point of the time after Rb injection ceased. However, Rb continued moving in heartwood probably by diffusion even after the cease of Rb injection. In a series of injection experiment, radial movement of injected Rb is not corresponding to the seasonality of both cambial activity and cytological changes of ray parenchyma accompanied with heartwood formation. From the results on Rb’s behavior, we conclude that accumulation of K and other alkali metals in heartwood of Japanese cedar has two steps, active transport from sapwood to outer heartwood via ray, and diffusion in heartwood, and that these processes proceed independently from both cambial activity and cytological changes of ray parenchyma.

Losses of elements in plant samples under the dry ashing process

Losses of trace elements in plant samples after dry ashing were investigated. Plant samples were heated in crucibles at 105–600°C for 0.5–24 hours in a muffle furnace. The amounts of elements remaining after heating were determined by INAA. The amounts of Cl and Br decreased over the range 200–400°C in all samples, especially in stem samples. The amount of Na increased over the range 450–600°C, possibly because of contamination from the crucibles. Dry ashing is suitable for analyzing most elements in plant samples.

Application of activable tracers to investigate radial movement of minerals in the stem of Japanese cedar (Cryptomeria japonica)

Two activable tracers, Rb and Eu, were injected into the sapwood of Japanese cedars (Cryptomeria japonica D. Don) to investigate the radial movement of minerals in their stems in the resting period. Eight trees of four cultivars, two of which genetically form wet heartwood, were treated near the end of the growing period. At 40 days after the treatment, Rb was detected in the outer heartwood, whereas Eu was not. Radial movement of Rb was more rapid in trees with wet heartwood than in those with normal heartwood. At 204 days after the treatment, more Rb was detected in the heartwood than was found on the first sampling, whereas no Eu was detected in the heartwood. The difference in radial movement between Rb and Eu was considered mainly to be the result of selective transport of beneficial minerals by Japanese cedar. The difference in the rate of radial movement of Rb between wet and normal heartwood became more conspicuous at 204 days after treatment. We concluded that the movement of Rb from the sapwood to the outer heartwood was by active transport through the rays, whereas that in the heartwood was by diffusion due to the gradient of Rb concentration.

MEASUREMENT OF TRACE ELEMENTS IN TREE RINGS USING THE PIXE METHOD

Abstract Standard materials were prepared in order to calculate element concentrations in tree samples using the particle induced X-ray emission (PIXE) method. Five standard solutions (1) Ti, Fe, Cu, As, Rb, Sr; (2) Ca, V, Co, Zn, As, Rb; (3) Ti, Mn, Ni, As, Sr; (4) K, Mn, Co, As, Rb, Sr; and (5) Ca, Mn, Cu, As, Rb, Sr, were added to filter papers. The dried filter papers were used as standard samples. Pellets of Pepperbush leaves (National Institute for Environmental Studies (NIES)) and Peach leaves (National Institute of Standards and Technology (NIST)) were used as references. The peak counts of Ca, Mn, Cu, Zn, Rb, and Sr in samples taken from a kaki ( Diospros kaki Thunb.) were measured and the concentrations (ppm) of the elements were calculated using the yield curve obtained from the standard filter papers. The concentrations of Mn, Zn, Rb, and Ca were compared with the data obtained from a separate INAA analysis. Concentrations of Mn, Zn, and Ca obtained by both methods were almost the same, but the concentrations of Rb differed slightly. The amounts of trace elements in samples taken from a sugi ( Cryptomeria japonica D. Don) were also measured.

A demineralization mechanism for Lake Balkhash

Lake Balkhash is one of the many closed lakes in Central Asia. Mechanisms of demineralization in Lake Balkhash were considered from results of surveys undertaken on the lake and along the Ili River. Electrical conductivity (EC) values at the eastern coast in south-western Lake Balkhash were higher than those of the western coast. The Ili River enters at the south-western corner of the lake, so that EC values of this area are low. This water flows westwards. The distribution of Ca2+ concentrations showed that these were lower value in Lake Balkhash than along the Ili River, implying Ca2+ removal by the lake. Amongst suspended mineral matter in the lake occur calcite and dolomite. Thus, a possible mechanism of calcium removal is that it is removed as crystals of calcite or dolomite. SO42− concentration within the lake has increased for the past 37 years. This may be caused by the discharge into the lake from the city of Balkhash of waste water from a copper smelter.

NON-DESTRUCTIVE NEUTRON ACTIVATION ANALYSIS OF PARTICLE SIZE FRACTIONS AND SOIL EXTRACTS

Abstract Non-destructive instrumental neutron activation analysis was examined. Using long-lived isotopes, La, Sm, Ce, Sc, Fe, Co, Cs, Th, Cr, Hf, and Tb, and using short-lived isotopes, Al, V, Na, and Mn in various particle size Tractions of clay, silt, fine sand, and coarse sind, and the oxalic acid extracts of the soil were determined. Relative standard deviations (CV) were in the range of 1.7 to 12%. The reliability of the analysis was also examined. Recovery percentages ere in the range of 87 to 120%. The analytical results of geochemical reference samples of JG-1 and JB-1 showed general agreement with the other workers results. Distribution patterns of those elements among the six fractions of highly weathered and ively unweathered soils were briefly discussed in relation to weathering processes.