Kunihiko Watanuki

Vertical distribution of organic constituents in an Antarctic lake: Lake Fryxell

Vertical distribution of organic constituents, i.e. total organic carbon (TOC), extractable organic carbon with ethyl acetate (EOC), hydrocarbons, phytol, sterols, fatty acids and phenolic acids in Lake Vanda was studied to elucidate their features in relation to the stratification of lake water and the distribution of lake organisms. The concentrations of TOC, EOC and sterols increased with depth and attained the maximum values of 25 and 1.5 mgC l−1 and 1.4 μg l−1 in the bottom, respectively, while those of fatty acids showed the maximum value of 61 μg l−1 at a depth of 55.4 m, along with the highest value of the ratio of unsaturated (UC16, uC18) to saturated (C16, C18) acids (8.5) and with the highest carbon preference index (35). Hydrocarbons were only found in the bottom layers (60.4 and 65.9 m) and bottom sediment. These results suggest strongly that the vertical distribution of lake organisms and their activity are quite different due to depth. In the bottom warm anoxic layers the degradation of organic materials must have occurred significantly and thus refractory organic materials should be concentrated.

Unusual distributions of long-chain n-alkanes and n-alkenes in antarctic soil.

Abstract Hydrocarbons in soil samples from the McMurdo Dry Valleys of southern Victoria Land, Antarctica, were studied to examine their features and to elucidate source materials. Normal-alkanes and n -alkenes were found at concentrations ranging from 13 to 2200 and from 1.1 to 5000 ng/g of dry soil, respectively. Unexpectedly, the major hydrocarbons were all odd-carbon numbered long-chain n -alkanes with maximum concentrations n -C 23 , n C 25 or n -C 27 . This may be due to the erosion of sedimentary materials containing vascular plant debris formed during the pre- and inter-glaciation periods of Antarctica (Miocene-Pliocene) and microbial debris, such as fungi and microalgae. Normal-alkenes maximize at n -C 23:1 (carbon chain length: number of double bonds), n -C 25:1 , n -C 27:1 or n -C 29:2 , which could be derived from cyanobacteria and microalgae, that lived in the past in the Antarctic cold desert and/or organic debris of wind-transported cyanobacterial mats.

Quenching and liquid chromatographic determination of polythionates in natural water.

Polythionates in highly acidic, crater-lake water have been determined by ion-chromatography and high-performance microbore liquid chromatography. The first technique allows the determination of tri-, tetra- and pentathionate in excess of 10 ppm, and the second allows analysis for tetra-, penta- and hexathionate in excess of 0.2 ppm. The methods for preserving polythionates in natural solutions are also discussed. The recommended procedures for storage are to add hydroxylamine hydrochloride to sample solutions or to exclude atmospheric oxygen by using Winkler oxygen-determination bottles, followed by storage in a refrigerator at 5 degrees .

Characterization of sulfate ion in travertine

The mode of incorporation of sulfate ion in travertine was discussed on the basis of chemical compositions, i.r. and laser Raman spectra. These data strongly suggest that most of the sulfate ions in the calcitic travertine replace carbonate ions. This conclusion is in good harmony with the facts that calcite incorporates more sulfate ions than aragonite does and that the sulfate content of manganoan calcite decreases with increasing manganese content (Takano et al. 1977). Based on this conclusion, retarding effect of sulfate ion on the precipitation of calcite from solution was discussed.

Hydroxy acids in Antarctic lake sediments and their geochemical significance

Abstract Hydroxy acids in sediments of Lakes Bonney, Fryxell, Joyce and Vanda, and unnamed ponds (B2, NF1, NF2 and L4) as well as in cyanobacterial mats from the McMurdo Sound region of southern Victoria Land in Antarctica have been studied to clarify their features and elucidate their source organisms. Normal and branched ( iso and anteiso ) 2-hydroxy acids were found in all the samples studied with the predominance of even- and odd-carbon numbers, respectively. The most dominant 2-hydroxy acids in the sediments were mainly short-chain components ( 20 ). Normal and branched 3-hydroxy acids were detectewith the predominance of even- and odd-carbon numbers, respectively, in total concentrations between 0.48 and 53 μg/g of dry sediment. (ω-1)-Hydroxy acids were all long-chains (C 22 , C 24 , C 26 , C 28 and C 30 ). 9,10-Dihydroxyhexadecanoic and/or 9,10-dihydroxyoctadecanoic acids were identified in all the sediments and a cyanobacterial mat. The composition of hydroxy acids differ considerably among the lakes and ponds, suggesting the difference of source organisms. These 2-, 3- and (ω-1)-hydroxy, and 9,10-dihydroxy acids may be derived from cyanobacteria and microalgae, in addition to non-photosynthetic microorganisms. Cyanobacteria and microalgae which are widely distributed in the world, may be important sources of hydroxy acids in the natural environments.

Organic geochemistry of the McMurdo Dry Valleys soil, Antarctica.

Abstract Organic geochemical studies of 12 soil samples from Wright and Taylor Valleys of the McMurdo Dry Valleys (Ross Desert) in southern Victoria Land, Antarctica, were carried out. Long-chain n -alkanoic acids (C 20 −C 34 ), with predominance of even-carbon numbers, were abundant in all the samples. 3-Hydroxy acids (C 8 -C 30 ) with a predominance of even-carbon numbers were found in the samples, together with 2-, ω- and (ω-1)-hydroxy acids. α,ω-Dicarboxylic acids (C 8 -C 31 ) were detected having near-unity values of carbon preference indices; mainly the C 13 dicarboxylic acid predominated. Visual kerogen revealed that amorphous materials are major components (68–98%) with small amounts of very fine coals (2–32%), but no woody and herbaceous materials. The occurrence of mature isomers of steranes and triterpanes, the paucity of n -alkenoic acids and data from the microscopic study suggest that organic components in the soil samples are derived from erosion of Beacon Supergroup sedimentary rocks and past biological debris containing vascular plan waxes as well as wind-transported cyano-bacterial mats, including cyanobacteria, microalgae, bacteria and fungi, rather than from living organisms.

Steranes and triterpanes in the Beacon Supergroup samples from southern Victoria Land in Antarctica

Steranes and triterpanes in Beacon Supergroup samples (sedimentary rock and silicified wood) from Allan Hills and Carapace Nunatak of southern Victoria Land in Antarctica were studied to elucidate sources of organic materials, sedimentary paleoenvironment and thermal history after deposition. Relative abundances of C27, C28 and C29 steranes and visual kerogen results of Beacon Supergroup samples from Allan Hills imply that organic materials in the sedimentary paleoenvironments are contributed mainly by vascular plants with some influence of microorganisms, while those of the Carapace Nunatak sample may be largely due to fern spores. The pristanephytane and pristaneheptadecane ratios of the samples were generally close to unity and between 0.50 and 0.99, respectively, suggesting that the sedimentary paleoenvironment was shallow lacustrine with alternating oxic and anoxic conditions. The (22S22R)-17α(H),21β(H)-C31-C33 triterpane ratios are approximately at thermal equilibrium values (ca. 1.5) in most samples, while the (20S20R)-5α(H), 14α(H), 17α(H)-C29 sterane ratios and the (20R + 20S)-5α(H), 14β(H), 17β(H)5α(H), 14α(H), 17α(H)-C29 sterane ratios vary from 0.0 to 1.1 and from 0.0 to 1.4, respectively. Most of the (20S20R)-5α(H), 14α(H), 17α(H)-C29 sterane ratios did not reach thermal equilibrium values. The correlation coefficient between the (20S20R)-5α(H), 14α(H), 17α(H)-C29 sterane ratios and (20R + 20S)-5α(H), 14β(H), 17β(H)5α(H), 14α(H), 17α(H)-C29, sterane ratios is very high (0.96). These variable maturities probably reflect thermal effects of basaltic dikes on the Beacon Supergroup at Allan Hills and Carapace Nunatak during Jurassic time. Thermal stresses on the Beacon Supergroup prior to basaltic intrusion have been estimated to be quite low, so the paleotemperatures of this formation have been quite low.

Geochemical features of hydrocarbons and fatty acids in sediments of the inland hydrothermal environments of Japan

Abstract Hydrocarbons, n-alkanes, acyclic isoprenoid alkanes, steranes and triterpanes and fatty acids were studied for 6 sediment samples from inland acid hydrothermal environments (Mounts Yakeyama and Tateyama areas and Lake Katanuma) in Japan to clarify their features and to elucidate their source organisms. Normal alkanes carbon chain length ranging from nC13 to nC35 and acyclic isoprenoid alkanes iC16, iC18, pristane, phytane and/or squalane were found, together with steranes and triterpanes. The major hydrocarbons were mainly odd-carbon numbered long-chain n- alkanes (≧ C 20 ) , such as nC29 and nC31. Normal alkanoic acids (nC10-nC34) were detected with the predominance of even-carbon numbers maximizing at nC16 and, nC24, nC26 or nC28), along with iso- and anteiso-branched (i, aC12−i, aC17) and n-alkanoic acids nC16:1 (carbon chain length : number of double bonds), nC18:n, nC20:n and nC22:n. These compounds can be attributed to various source organisms bacteria, cyanobacteria, microalgae and vascular plants in and around the hydrothermal environments. Low concentrations of hydrocarbons and fatty acids may reflect the low primary productivity of their harsh environment, but the abundances of n-alkenoic acids reflect that fresh organic matter is continuously supplied by microbial activity and vascular plants. The (22S/22R)-17α,21β(H)-30,31-bishomohopane ratios (0.85–1.5) and (20S/20R)-24-ethyl-5α(H), 17α(H)-cholestane rations (0.25-0.80) revealed that the thermal alteration of biologically synthesized configuration has taken place to a large extent in the hydrothermal environments.