INVESTIGATION ON THE BIOLOGICAL AND CHEMICAL MARKERS OF THE ACIDIFICATION OF LAND WATERS

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The purpose of this project was to find out certain chemical and biological indicators such that represent environmental conditions of the aquatic systems significantly affected by acidification. Particular attention was paid on organic molecules in sediments, since they might be used for molecular fossils of the microbial community which are expected to be distinctly sensitive against improverishment of the water quality. Lipid molecules and diatom frustules remaining in some lacustrine sediments were surveyed for lakes known as "inorganically acidic lakes"(pH=3-5) in Japan. They are under the influence either of acid hot springs dissolving volcanic gasses or ground waters percolating sulfide minerals contained in the igneous rocks. Some lakes have experienced conspicuous alterations of the water quality in the near-past, due to artificial or natural events such as an excavation of the waterway introducing an acidic river water to the lake or an earthquake occurred in the near-by site. lon chromatograph analyzer purchased in this project was used for description of the water quality in the watersheds and the lakes. Analyzes by use of gas chromatograph and gas chromatograph-mass spectrometry demonstrated in many lake sediments an occurrence of the peculiar nature of long-chain branched hydrocarbons, alcohols and fatty acids identified as anteiso structural isomers. Coincidental occurrences or absence and similar vertical variations between these organic molecules and certain kinds of diatom frustules in accordance with the historical events, suggested that they can be promising biogeochemical indicators of the lake acidification, although their source organisms remain to be unraveled.