Noriko Shinozuka

Vertical distribution of fluorescent organic matter along with AOU and nutrients in the equatorial Central Pacific

Abstract The vertical profiles of fluorescent organic matter were studied at five stations in the equatorial Central Pacific. At every station, seawater fluorescence was low in the surface layer, indicating photochemical decomposition of fluorescent organic matter. Seawater fluorescence increased steeply with depth to a maximum at about 300 m depth and then decreased slightly, showing a minimum at 500–600 m depth, and then increased again slightly, exhibiting a broad maximum around 1000 m depth; thereafter it was almost constant or decreased slightly. This vertical distribution is similar to that of AOU, nitrate and phosphate. The observed linear correlations between fluorescence intensity and AOU, nitrate and phosphate in the middle layer (300–1000 m depth) are consistent with results in the North Pacific and the coastal seas of Japan. Among the parameters, the linear relation between AOU and fluorescence intensity is highest. Since AOU is a parameter of oxygen consumption, the high correlation between AOU and fluorescence confirms our previous observation that fluorescent organic matter is regenerated in the water column by oxidation and remineralization of organic substances on the sinking particles, as in the case of nutrients. On the other hand, a contribution of the fluorescent organic matter to the dissolved organic matter with regard to oxygen consumption in the water column is discussed in conjunction with “Redfield” ratios in the ocean.

AGGREGATE FORMATION OF HUMIC ACIDS FROM MARINE SEDIMENTS

Abstract Humic acids were extracted from marine sediments and the aggregate-forming properties were studied by surface tension measurements and the solubilization of hydrocarbons. The surface tension of aqueous humic acid solutions decreases with the humic acid concentration and becomes constant; the relationship between the surface tension and the logarithm of the concentration of humic acid is represented by two straight lines. The break point is considered to be due to aggregate formation. The solubility of benzo(a)pyrene and icosane in humic acid solution increases with humic acid concentration. A marked solubility increase observed at a humic acid concentration near 0.1% indicates that the hydrocarbon is solubilized in humic acid aggregates. The concentration of aggregation can be determined from the point of intersection of two straight lines representing the relationship between solubility of hydrocarbons and log concentration of humic acid. Concentrations of aggregate formation for various humic acids determined by surface tension measurements and by the solubilization of hydrocarbons are in good agreement.

High-performance liquid chromatographic determination of catecholamine metabolites and 5-hydroxyindoleacetic acid in human urine using a mixed-mode column and an eight-channel electrode electrochemical detector

An HPLC system for the simultaneous determination of acidic catecholamine metabolites, related compounds and 5-hydroxyindoleacetic acid (5-HIAA) in human urine was developed. A mixed-mode (C18/anion-exchange) column with isocratic elution using citrate buffer and an eight-channel electrochemical detector were used. Vanilmandelic acid (VMA), 3,4-dihydroxyphenylacetic acid (DOPAC), 4-hydroxy-3-methoxyphenyllactic acid (vanillactic acid, VLA), homovanillic acid (HVA), vanillic acid (VA) and 5-HIAA in urine were determined simultaneously. Detection limits and inter (n = 5) and intra-assay (n = 5) coefficients of variation were satisfactory. The mean of analytical recoveries (n = 3, +/- C.V. (%)) were between 97 +/- 3.2 (VMA) and 105 +/- 4.8 (VA). Correlations between the analytical results for VMA, HVA and 5-HIAA obtained by an established method and the present method were satisfactory. The mean +/- 2 S.D. of the excretion rates of VMA, DOPAC, VLA, HVA, 5-HIAA and VA in urine from healthy adult volunteers were 0.61-4.36, 0.13-1.02, 0-0.35, 0.67-6.55, 0.50-5.14 and 0-0.55 mg/g creatinine, respectively.

Polarographic determination of critical micelle concentration of anionic surfactants

SummaryCritical micelle concentrations of four anionic surfactants were determined by DC polarographic desorption waves of the surfactants without supporting electrolyte. The linear plot obtained between the potentials of the desorption waves and the logarithmic concentrations of the surfactant had an inflection point which corresponded to the CMC. The CMC values obtained are in good agreement with those in the literature.ZusammenfassungEs wurden die kritischen Mizellbildungskonzentrationen (KMK) von anionischen Tensiden durch Gleichstrompolarographie in Abwesenheit von Leitelektrolyten bestimmt.

Solubilizing action of humic acid from marine sediment

Abstract Humic acids extracted from marine sediments increase the water solubility of hydrocarbons. The solubilities of n-alkane and polyaromatic hydrocarbons increase sharply with humic acid concentration below 0.01% and levels off between 0.01–0.1%. Above 0.1% of humic acid, the solubility again markedly increases. The solubilizing action of humic acid is discussed in relation to its surface active properties.

Polarographic characterization of humic acid

We examined humic acids polarographically and observed a peak current in differential-pulse polarograms. The current showed a linear relation against the humic acid concentration, and the concentration at which a linear relation was broken indicated the aggregate formation. The effects of pH, temperature, and molecular weight on the current were also studied. The current was also related to the acidity of humic acid.

Absorption of nitrogen dioxide in organic solvents

The absorption of NO(2) at low levels in nitrogen, by N,N-dimethylformamide (DMF) and dimethyl sulphoxide (DMSO), has been investigated. Parts-per-million levels of NO(2), were collected with an efficiency of 90% in DMF and 65-70% in DMSO. The absorption efficiency in DMF depends on the gas flow-rate and the bubbling time, but in DMSO it is independent of time.

The Effects of Goethite on Formation of Chloro Compounds from the Chlorination of Hydroxybenzoic Acids in Water.

水の塩素処理によるヒドロキシ安息香酸類からの有機塩素系化合物の生成におよぼすゲータイト(GT)の影響を明らかにするため,ヒドロキシ安息香酸類のGTへの吸着量および吸着状態を調べたのち,GT上への吸着状態でのヒドロキシ安患香酸類の塩素化の結果を,遊離の状態での結果と比較した。ヒドロキシ安息香酸類の吸着挙動とFT-IRスペクトルから,化学吸着の存在が示された。r12一ヒドロキシ安息香酸(MHBA)およびρ-ヒドロキシ安息香酸(PHBA)では,カルボキシル基のみがGT表面の鉄に配位するが,サリチル酸(SA)では,低濃度領域において,フェノール性ヒドロキシル基とカルボキシル基の両方で鉄に配位するキレート吸着が支配的である。塩素化におよぼすGTの影響として,一つには表面ヒドロキシル基の交換によるものがあり,これはすべてのヒドロキシ安息香酸で認められた。吸着状態に起因する影響は,MHBAおよびPHBAの場合にはあまりみられないが,SAではpH4緩衝液においてGTの存在によりクロロホルム(CF)およびトリクロロ酢酸(TCA)生成量が減少した。この結果は,SAがGTに強くキレート吸着するためと考えられた。

Rotating-disc electrode determination of nitrogen dioxide concentrated in N,N-dimethylformamide

Nitrogen dioxide at ppm levels in air is concentrated in N,N-dimethylformamide and determined by voltammetry at a rotating-disc electrode. The oxidation currents for nitrite are measured under the same conditions as the nitrogen dioxide reduction and are used as standards. The results are in good accordance with the values calculated from the absorption measurements.