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

摘要

Lake Baikal, located in southeastern Siberia (51-56° N, 104-110° 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~3). 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 oligo-trophic in spite of its age (25 million years). Chemical compo-sition and nutrient concentrations of the lake have been ob-served 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 indus-trial 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).