Kan Kimura

Lead behavior in abalone shell

Abstract In order to gain information about the behavior of heavy metals in biological assimilation processes in a marine food chain and to investigate the possibility that lead pollution in a marine environment can be estimated by measurement of a small number of key materials from such a food chain, muscle and shell were analyzed from abalone (Haliotis) from a shallow water locality in a Japanese coastal region. Lead concentrations in muscle were about 26 ppb for abalone of approximately 3 years old and decreased systematically with increasing age of animals sampled, to about 3.3 ppb for a specimen approximately 8 years old. Lead concentrations in shell material gradually decreased also, from 150 ppb to 82 ppb in the oldest specimen. The decrease of concentration in tissues with increasing age indicates that a mechanism for exclusion of lead during tissue growth becomes more efficient with age. Along the food chain in which abalone is the final stage, lead was enriched at the first stage, from seawater to algae, by a factor of 100. Lead was diminished at all subsequent stages of the chain. Tissue of artificially cultured abalone had four times higher lead values compared to abalone grown in natural conditions, and this appears to reflect the fact that lead concentration was three times higher in seawater in the cultured environment.

Determination of lead in geostandard rocks by electrothermal atomic absorption spectrometry after isolation of lead with yield monitoring

Abstract Lead contents in geochemical rock standards of the Geological Survey of Japan and U.S. Geological Survey, were determined with coefficients of variation less than 5%. After dissolution of the rock by hydrofluoric and nitric acids, and spiking with 212Pb, lead purified by extraction with dithizone, appropriate corrections being applied to the final results.

Tritium production process ‐ comparison between neutron emission rate and tritium production rate

When the electrolysis of 0.5 M D2SO4‐D2O solution was carried out using Pd or palladized Pd as a cathode material and Pt as an anode material, the emission of neutrons was detected by means of the fission track method and the production of tritium was investigated with a liquid scintillation method and a TPD using a mass spectrometer. The emission rate of neutrons was in the same orders of magnitude as the neutron flux in the background (10−3 s−1). Otherwise, the existence of tritium in the cathode material after the electrolysis was identified by the measurement of the β‐ray emission when the specimens were immersed in the liquid scintillator. Moreover, mass peaks of m/z=5 and 6 which were considered due to DT as well as T2 were identified in TPD, through the resolution of the mass spectrometer was not so high. The tritium production rate estimated by the β‐ray emission measurement was size orders of magnitude larger than the neutron emission rate. The difference betweeen them are briefly discussed.

Determination of Zirconium in Natural Water by Spectrophotometry following the Concentration Step with Yield Tracer

Zirconium in natural water samples was determined spectrophotometrically after concentration using95Zr as a yield tracer. Acidified sample (1l) with a known amount of 95Zr was evaporated to dryness, treated with hydrofluoric and nitric acids, and then with nitric and perchloric acids, and evaporated nearly to dryness. The residue was taken up with 2 M perchloric acid and zirconium in the solution was extracted with 0.1 M thenoyltrifluoroacetone (TTA) in benzene. The TTA complex solution was converted to hydrochloric acid solution. After the recovery yield was estimated by measuring the radioactivity of 95Zr in the final solution, zirconium was then determined by spectrophotometry with Arsenazo III. Zirconium contents in lake and hot and cold spring samples from Nikko and Shiobara districts were found to be 0.29-2.8 microgram/l by this method.