Features and sources of organic components in surface sediments of Lake Nishi-inbanuma in Chiba prefecture, Japan
2006
Matsumoto, G.(Otsuma Women's Univ., Tokyo (Japan)) | Akutsu, Y. | Takamatsu, N.
Lake Nishi-Inbanuma (area 680 ha, average depth 1.8 m) in northwest Chiba Prefecture, Japan, is known as a typical eutrophic lake. We studied organic components in the surface sediments (0-5 cm) of the lake to elucidate their features and sources. The lake's high total organic carbon (TOC) contents (3.41-7.18 % with an average of 5.54%) revealed it as a typical eutrophic lake. Normal-alkanes maximizing at n-C29 with a predominance of odd-carbon numbers were detected, together with squalane and UCMH (unresolved complex mixture of hydrocarbons). Stenols and stanols (C27-C29) in the lake sediments originated from plankton and vascular plant debris. Stanols are probably derived from diatoms and dinoflagellates as well as to the influence of a selective degradation and reduction of stenols in the sediments. The contribution of autochthonous organic matter (47.1-72.2 % with an average of 62.8 %) was greater than that of allochthonous organic matter. The latter is mainly supplied from the Shinkawa and Kashimagawa Rivers along with the influence of petroleum products.
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