Noboru Okubo

Determination of trace levels of total carbonate-carbon by indirect photometric ion chromatography with nitrogen purging

Abstract Purging with nitrogen substantially prevented atmospheric carbon dioxide from dissolving in the eluent used in indirect photometric ion chromatography. Total carbonate-carbon at trace levels could be determined as hydrogencarbonate by this method. By using an analytical column (250 × 4.6 mm I.D.) packed with MCI SCA-02 and 5.0 · 10−4M sodium hydrogenphthalate—1.5 · 10−4M N-2-hydroxyethyl-piperazine-N′-2-ethanesulphonic acid (HEPES) (pH 6.5) as the eluent, hydrogen-carbonate was detected as a negative peak at 250 nm. The detection limit (signal-to-noise ratio = 2) was 1.4 · 10−11 mol (7 · 10−7M with an injection volume of 20 μl) and the calibration graph was linear from 3.0 · 10−11 to 3.8 · 10−9 mol (r = 0.994). The coefficient of variation was less than 2% on injection of 4 · 10−10 mol. Total carbonate-carbon at levels as low as 10−4-10−6M level could be determined accurately. The errors in the analysis of practical samples by the method without nitrogen purging are demonstrated.

Acidity in winter time deposition on the Japan seaside of Japan

Abstract The extent to which weekly precipitation samples are representative of acidity in precipitation on the Japan Sea side of Japan was analyzed with respect to daily wet deposition samples. In comparison to weekly deposition samples, the pH of daily deposition samples is distributed in a narrow range between pH 4.2 and 5.0. Weekly samples of higher pH appeared to be inflated by excess Ca2+ which was emitted from road dust. The average annual pH remained nearly constant during the six winters of the study.

An estimation of the contribution of the sulfate ion to rainwater acidity

Abstract A new method to estimate the contribution of sulfate to acidity in rainwater is proposed. The application of the method was demonstrated using rainwater data collected at Kanazawa, an area of low industrial activity on the Japan Sea side of Japan. Contribution percentages of SO4 2− to acidity in rainwater of a pH between 4.0 to 4.6 were approximately 70% during non‐winter weather, and about 85% during winter. Results were also compared to estimates based on the wide‐spread method of using excess sulfate (non‐seasalt derived sulfate) for the estimation of acidity.

Studies on Metals in Environment. III. Seasonal Variations in the Amounts of Chromium in Deposits and Correlation of Chromium with Other Components in the Deposits

Chromium is a biologically significant metal which is present in the environment. This paper describes a study of seasonal variations in the amounts of chromium and several other components in deposits regularly collected from the air in Kanazawa city during one year. The concentration of chromium amounted to 0-1.1 ppb and was comparable to those of chromium in the sea and natural waters. Several other components in the deposits were also determined and correlations among the components, including chromium, were investigated. The seasonal variation of chromium in the deposits collected at this spot showed that the meteorological conditions considerably influenced the profile of chromium in the deposits. Another important factor is artificial sources such as fuel combustion for industrial and domestic purposes. Among the components in the deposits, magnesium and chloride contents were fairly closely correlated with chromium, and sulfate was also correlated with chromium though less closely. The possible origin of chromium in the deposits is discussed.