Tetsu Kumagai

Distribution of dissolved organic carbon and dissolved fulvic acid in mesotrophic Lake Biwa, Japan

The dissolved organic carbon (DOC) concentrations in mesotrophic Lake Biwa were determined by a total organic carbon (TOC) analyzer, and DOC molecular size distributions were determined by size exclusion chromatography (SEC) using a fluorescence detector at excitation/emission (Ex/Em) levels of 300/425 nm with the eluent at pH 9.7. The fluorescence wavelengths for detection were chosen from the result of excitation–emission matrix spectrometry (EEM) analysis for dissolved fulvic acid (DFA) extracted from Ado River (peak A, Ex/Em = 260–270/430–440 nm; peak B, Ex/Em = 300–310/420–430 nm). Ado River DFA was eluted with a retention time (RT) of 7.4–8.9 min and the apparent molecular weight was estimated at 22–87 kDa based on the elution curve for the spherical protein molecular weight standard. A DFA peak eluted at the same retention time as Ado River DFA also appeared in all the samples of Lake Biwa water. From the linear relationship between the peak areas with an RT of 7.4–8.9 min by SEC analysis and DOC values of DFA by TOC analysis of a series of DFA samples (r2 = 0.9995), the concentrations of DFA in the lake water were roughly calculated. DFA was distributed within the range 0.25–0.43 mg C l−1 and accounted for 15%–41% of DOC, with the highest ratios observed at a depth of 70 m in August and the lowest at 2.5 m in May.

Distribution of dissolved organic carbon in lakes of different trophic types

The distributions of dissolved organic carbon (DOC) in the warm season were elucidated in ten lakes of different trophic types in Japan, Russia, and China. DOC showed similar vertical distributions in all the lakes in summer when thermal stratification occurred. DOC in the epilimnion was higher than the value of 0.8 mg C l−1 found in the hypolimnion. In three Japanese lakes, hypolimnion DOC was negatively correlated with apparent oxygen utilization (AOU), reflecting the net oxidation of DOC using the dissolved oxygen in lake water. The DOC : O2 ratios (0.115–0.179), calculated by the slopes of the regression lines of DOC versus AOU in hypolimnion water, were as low as those of deep-sea water, which indicates low bioavailability of lake water DOC for heterotrophic bacteria. DOC and conductivity did not correlate well except in two Japanese lakes: one showed a positive correlation and the other a negative correlation, indicating DOC loading from the inflowing rivers. Eutrophic lakes tended to have higher DOC values than meso- and oligotrophic lakes, and DOC values in the surface water negatively correlated with Secchi depths.

Gravimetric determination of copper with 2-hydroxy-1-naphthaldoxime

Abstract A gravimetric method for the determination of copper with 2-hydroxy-1-naphthaldoxime (HNA) has been studied. The HNA quantitatively precipitates copper as Cu(C11H8NO2)2 which can be used as a weighing for copper; the gravimetric factor is 0.1458. Iron, aluminum, chromium, and commonly accompanying elements do not interfere. The method can successfully be applied to the determination of copper in aluminum base alloy.

Characterization of UV-absorbing organic matter in Lake Biwa using high-performance liquid chromatography/mass spectrometry

Dissolved organic matter (DOM) is a major portion of organic matter in the aquatic environment and operationally defined as the organic materials that pass through a filter with pore size 0.1-0.7 f.!m. DOM has various important roles in the environment. lt is one of the important carbon reservoirs in the global carbon cycle (HEDGES 1992), a main energy source of aquatic heterotrophic bacteria (AZAM et al. 1983), and it controls the attenuation of ultraviolet radiation in water (WILLIAMSON & ZAGARESE 1994). Recently, the solar ultraviolet radiation reaching the earths surface has increased due to anthropogenic diminishing of the ozone layer in the stratosphere (FARMAN et al. 1985). Solar ultraviolet radiation has harmful effects not only on terrestrial plants and animals but also on aquatic organisms (HoDOKI & WATANABE 1998). Recent studies have suggested that UV-B radiation (280-320 nm) alters the balance between the biological processes producing organic materials and chemical and microbial processes degrading them (ZEPP et al. 1998). Observations in aquatic ecosystems have shown that, in stratified waters, exposure of solar UV radiation promotes net decreases of chromophoric dissolved organic matter (CDOM) and results in increases o f UV-B penetration into the water colurnn (HADER et al. 1998). The distribution and characteristics of UV absorbing organic matter such as CDOM in aquatic environments must be known to understand its influence on the aquatic ecosystems; however, information about the chemical structure or origin of it is limited. In this study, our aim was to characterize UV-absorbing organic matter in Lake Biwa using high-performance liquid chromatography (HPLC) with reverse phase octadecy silica column and investigate the mass distribution ofthe separated organic molecules using electrospray ionization mass spectrometry (ESI-MS).

Role of allochthonous organic matter in Lake Baikal investigated using a 3-dimensional fluorescence excitation-emission matrix spectroscopy and high performance liquid chromatography-mass spectrometry

Lake Baikal, located in southeastern Siberia (51-56° N, 104uoo E; Fig. 1), is one of the largest freshwater lakes in the world, with the deepest (1643 m) water depth and the largest water volume (23 000 km). It is famous for its high clarity and water quality and important freshwater resources for human life in the surrounding area. Because of the low population density and human activities in its watershed, it remains oligotrophic in spite ofits age (25 million years). Chemical composition and nutrient concentrations of the lake have been observed by Russian researchers since from the 1990s. Nutrient values were low from 1950 to 1997, but began to increase around 1998 (SoROKOVIKOVA et al. 2000). Rapid changes in the watershed due to increasing human activities, such as industria! development, forest destruction, or enhanced agriculture in recent years have changed the lake ecosystem, and signs of eutrophication are often observed in summer (NAKANO et al. 2003, KATANO et al. 2005). Dissolved organic matter (DOM) is organic matter operationally defined by the particle size of <0.2 11m and constitutes a major portion of organic matter in water. YosHIOKA et al. (2002) reported that dissolved organic carbon (DOC) concentrations of Lake Baikal are 0.88-1.14 mg/L at offshore, and 3.20-1.15 mg/L at the rivermouth of the 2 inflowing rivers. These DOC values are the same level as Lake Biwa (SuGIYAMA et al. 2004, 2005). The chemica1 and biochemica1 properties of DOM are important: DOM strongly affects the stability or chemical forms of dissolved trace inorganic and organic materials in water by complexation; it controls UV radiation to lake water (WITTERS et al. 1990); and it is a major energy source of hetelotrophic bacteria (TRANVIK 1992). We characterized DOM, including allochthonous and autochthonous origins, an d elucidated the dynamics o f terrestrial DOM in the lake water using 2 analysis methods: 3-dimensiona1 fluorescence excitation-emission matrix (3D EEM) spectroscopy and high performance liquid chromatographyLake Baikal N

Flow injection analysis of ammonium ion by using thymol

水中のアンモニウムイオンをフローインジェクション法により定量する方法について検討した.蒸留水はキャリアー流として1ml/minの流速で送液され, これに100μlの試料溶液を注入する.1.2%水酸化ナトリウム水溶液と4%チモール溶液も1ml/minの流速で試薬流として送液され, 反応コイル (5m, 80℃) 中でインドフェノール型化合物が生成する.この吸光度を676nmで測定する.検量線の直線性は良好で (r=0.9997) , 5mg/lのアンモニウムイオンの10回の繰り返し注入における相対標準偏差は0.62%であった.本法によって1時間当たり60試料の分析が可能である.

Cation Exchange Studies of Cadmium Chloride, Bromide and lodide Complexes in Aqueous Acetone Solution

The distribution equilibria between cadmium (II) chloride, bromide, iodide and perchlorate complexes and the cation exchange resin in aqueous acetone solutions have been investigated. Formation constants of cadmium halides or perchlorate have been calculated from the distribution coefficients of cadmium in aqueous acetone solutions containing 10, 20, 30 and 40 v/v% water. Cadmium concentrations of the solutions have been measured by the atomic absorption spectrophotomer equipped with a carbon tube atomizer. The logarithmic values of constants in 10 v/v% aqueous acetone are: β1Cl =6.25, β2Cl =11.05 and β3Cl =14.59 for cadmium chloride, β1Br=6.97 and β2Br=10.35 for cadmium bromide, β1I=7.02 and β2I=11.80 for cadmium iodide, β1ClO4=2.18 for cadmium perchlorate. Formation constants of cadmium chloride are lower than those of cadmium iodide because of soft basicity of cadmium.