Organic matter distribution in the sediment of two riverine lakes of Kahayan River, Central Kalimantan

The highest average of water content (72.88 ± 3.17 %) in Lake Tabiri-Lake Takapan Complex was observed in Station A that was located in the middle of Lake Tabiri (Table 1). The particles of sediment that The lowest water content (51.99 %) was observed in Station B. Station B is the station that was located in the mouth of connecting channel that links Lake Tabiri with Lake Takapan. The samples that had already furnaced at 600° C for two hours will leave a non organic material, which is further refer as the "furnaced sediment". Preliminary observation on the appearance of the furnaced sediment in Station A show a whitish colour, that was suspected to be comprised of siliceous material. Meanwhile the colour of the furnaced sediment in Station B shows brownish red material that was probably consisted of iron containing material. Chemical analyses of the furnaced sediment will reveal the composition of this material. Highest concentration of organic matter (38.2 %) was also observed in Station A but the lowest organic matter concentration (9.97 % dry) was found in Station D. Station D is the Lake Takapan area where we usually can observes the River Kahayan plumes. Actually the water that was flow to Lake Takapan in this station, either it was refer as Lake Tabiri Plumes (D1-D3) or River Kahayan Plumes (D4-D6) is similarly originated from River Kahayan that water have the yellowish-white colour (HARTOTO & YUSTIAWATI 1999). The yellowish -white colour of River Kahayan water indicate that it contain a lot of iron compound. Highest organic matter observed in Station A probably due to its location in the middle of Lake Tabiri peat swamp forest system.