Heavy metals pollution in rivers at Tanjung Puting National Park, Central Kalimantan

A study to reveal the state of heavy metals pollution in Tanjung Puting National Park is conducted in 1995. Monitoring of iron, manganese, lead and mercury contents in water column, fish and sediment was done based on three sampling times at several sampling sites in River Sekonyer (buffer zone) and River Buluh Besar (core zone). Water samples were taken as a composite of the upper and bottom layer. Sediment samples were collected from the riverbed using Ekman-Bridge Grab. Fish samples were taken only from River Sekonyer. Analysis of heavy metals was conducted using wet and dry ashing method prior to measurement by Flame-Atomic Absorption Spectrophotometry (AAS) but for mercury, the measurement was done by Cold-vapor-AAS method. Water and sediment samples were digested with HNO3 before analysis with the AAS method. The results show that River Sekonyer water contained 0,099 mg Hg/L (990 times higher than that of safe consentration). 0.181 mg Pb/L (181 times), 0.273 mg Fe/L and 0.069 mg Mn/L. Meanwhile, River Buluh Besar water contained 0.177 mg Hg/L (1770 times), 0.105 mg Pb/L (1.05 times), 0.578 mg Fe/L and 0.035 mg Mn/L. In average, River Buluh Besar sediment had iron (2851,703 mg/kg, dry wight) and mercury (22.742 mg/kg) concentration higher than in River Sekonyer, that were 1061.756 and 7.859 mg Hg/kg respectively. Lead concentration in River Sekonyer, both in water (0.181 mg Pb/L) and sediment (16.308 mg Pb/kg) were higher than the concentration in River Buluh Besar (0.105 mg Pb/L and 3.532 mg Pb/kg). Apparently, high activity of illegal gold mining and the usage of petroleum with its tetraethyl lead additive for motorboat fuel, contribute to this phenomenon. Average heavy metal bioconsentrations in fish are 5.805 1.155, 12.540 and 0,005 mg of heavy metal atom/kg (dry weight) for lead, mercury, iron and manganese respectively.