Kazuo Fukushima

Geochemistry of hydroxy acids in sediments. I : Some freshwater and brackish water lakes in Japan

Abstract Series of α, β, ω and (ω-1) hydroxy fatty acids (FAOHs) were determined in several freshwater and brackish water lacustrine sediments in Japan. Analytical procedure used was digestion of the solvent-extracted sediment with HF/HCl followed by solvent and saponification extraction of the residue. Abundances of α/β and ω-FAOH determined by this procedure were 2–3 times higher than those obtained by single alkaline saponification and of the same order with those provided by HCl hydrolysis. Major portion of α/β-FAOH was obtained by solvent extraction of the acid-treated sediments, while subsequent alkaline saponification was needed for the majority of ω-FAOH to be recovered. Thus determined FAOHs comprised 33–61% (Av. = 42%) of the “bound” acid constituents in the lacustrine surface sediments. The α/β and ω-FAOH composition was principally the same among the samples examined, except for relative proportions of the iso to anteiso C 15 and C 17 s(α)-FAOH, which showed significant variations in the ranges of 0.30–1.1 and 0.46–1.5, respectively. In the holomictic lakes, the ratios together with the same ratios of the “bound” branched monocarboxylic acids tended to decrease with increasing water depth of the lakes, suggesting that the ratios may indicate an extent of the early diagenetic alteration of the bacteria-derived lipids either in water column or in surface sediment.

Geochemistry of hydroxy acids in sediments—II. Estuarine and coastal marine environments

Abstract Homologous series of α/β, (ω-1) and ω-hydroxy fatty acids (FAOHs) were analyzed in relation to their geochemical implication in estuarine and coastal marine environments. Mineral digestion with hydrofluoric/hydrochloric acid followed by alkaline saponification was used for determination of both “acid-labile” and saponifiable FAOHs in modern sediments. Sediment samples examined in the present work were collected from the shallow Tokyo Bay and deep Sagami Bay areas in Japan. A short sediment core, major river mouth sediments and suspended particles in the region were also examined. The most remarkable variation observed was the iso/anteiso abundance ratios of branced C 15 and C 17 β(α)-FAOH, which were high in the river mouth sediments, suspended particles and surface layers of the core sediment. The ratios decreased with increasing burial depth and with the distance from the river mouths or from the shore line. This fact suggested that the ratios might indicate the extent of short term early diagenetic alteration of bacteria-derived organic matter. Another point inferred was the abundances of C 22 –C 26 α(β)-FAOH and C 16 –C 28 ω-FAOH, both of which were elevated considerably in the river mouth sediments. The abundance of these long-chain α(β) and ω-FAOH was thought to indicate eventually the deposition and/or active microbial reworking of the terrigenous higher plant debris at the freshwater/seawater interface.

Relationships between stream water chemistry and catchment geology in a mountainous region in Nagano Prefecture, Japan II: mid to southern part along the Median Tectonic Line

Abstract Major ion concentrations were determined for a large number of stream water samples collected from the mountainous area around the Median Tectonic Line (MTL) in the mid to southern part of Nagano Prefecture, Japan. The MTL, a major fault in the accretionary sedimentary complex to Japan Arc, extending linearly in the east–west direction in southwest Japan, bends in this area to south–north along the Akaishi Mountain chain. To the east of the MTL are, in order, Jurassic metamorphic rocks, including black/green schists and ultra-basic serpentinite (Sambagawa-Mikabu Belt); Jurassic mudstone with voluminous chert and calcite (Chichibu Belt); and Cretaceous sandstone (Shimanto Belt). On the other hand, on the west side of the MTL, Cretaceous granitic rocks (including tonalite and quartzdiorite) intruded and significantly metamorphosed the Jurassic sedimentary systems (Ryoke-Belt). In this area, more than 200 water samples were collected from small streams. Ion concentrations were analyzed by ion chromatography, whereby higher ion concentrations relatively rich in Mg2+ and Ca2+ and lower concentrations relatively rich in Na+ were obvious for the streams in Sambagawa-Mikabu, Chichibu, and Ryoke Belts, respectively. These tendencies could be explained by whole rock analysis on XRF (X-ray fluorescence spectrometry) as well as by a preliminary leaching experiment of the powdered rock samples with water. The results strongly suggested that the analytical data of the major ions in the stream waters might be compiled into a hydrogeochemical map, corresponding to the geological map.