The Level of Humic Acid at Various Type of Inland Waters in Central Kalimantan

A study on elucidation of variation of humic acid concentration in various type of inland waters at Central Kalimantan was conducted from 1995 to 1997. The Information on the level of humic acid in inland water is one of the foundation in development of criteria for evaluation of resources. This study was aimed to reveal the spatial and temporal variation of humic acid level in oxbow lakes, low land lakes and rivers. In this study, composite water samples was taken from the Oxbow Lake Type I (Lake Lutan), Oxbow Lake Type II (Lake Rengas), Oxbow Lake Type III (Lake Takapan), low land lakes (Lake Sembuluh), main river (River Kahayan and River Buluh Besar) and tributary river ( River Rungan and River Sekonyer). The results showed that the highest humic acid concentration were found in November 1996 in Lake Lutan, Lake Rengas and Lake Takapan which were 721.357, 654.928 and 854.067 mg.l-1 respectively. It was found that oxbow lake had higher concentration of humic acid than low land lake. The lowest concentration of humic acid (44.774 mg.l-1) was observed in Lake Sembuluh on July 1995. The level of humic acid in River Sekonyer and River Buluh Besar did not significantly differed. Variation of humic acid level between sampling in each inland water was evaluated. The evaluation revealed among that the lotic habitat had higher concentration of humic acid than the lentic ones. The mechanism of this pattern was discussed. Oseanologi dan Limnologi di Indonesia, No. 39.