Tatsuya Koumoto

The geochemical characteristics of sediment in Tondano Lake, Indonesia : heavy metals and organic matter contents, and grain size distribution

Sediment quality of Tondano Lake, Indonesia has been investigated through measuring the geochemical characteristics such as the content of heavy metals, organic matter and grain size distribution; and also the relationship between heavy metals and organic matter, and between heavy metals and grain size distribution. These could be used as preliminary data for the purpose of evaluating lake condition as a part of freshwater ecosystem. The Tondano sediment had contained some heavy metals such as Cr, Cu, Hg, and Zn; where Cr and Zn, both less than the Sediment Quality Guideline (SQG), but Cu and Hg were well within the SQG. Organic matter content was highest at the northern outlet area, with the lowest amount at the southern inlet area. Grain size distribution was mostly dominated by sandy-loam clay (the highest content was at central lake). This was a result of intensive agricultural activities surrounding the lake, which brought sand grain via rivers from all areas to the central lake. The heavy metal contents were not found to be correlated with the organic matter, nor the grain size distribution (clay content).