Variability in physico-chemical parameters of Pachin river (Itanagar).

The concentration of water quality parameters in river and heavy metals in the bed sediment were measured for Pachin River for the three major flow periods. The pH, temperature (degree C), conducity (microS cm-1), DO, COD, NH3, PO4, total hardeness and alkalinity (mg/L) were found in the range of 12 to 22, 6.90 to 7.69, 25 to 211, 5.0 to 12.5, 10-115, 1.2 to 12.0, 0.05 to 0.62, 14 to 45, and 12 to 35, respectively. The heavy metals as Zn and Se showed an enrichment of 1 to 25, and 5 to 120, with concentration (microgram/g) range of 8 to 385 and 0.5 to 6.0, for the respective metal, in the labile fraction of the bed sediment. The variability in the physico-chemical parameters for different flow periods may be assigned to dilution of river water by direct runoff, human activities and organic load. The correlation study of physico-chemical parameters shows that their source of entering the river system is the same whether it may be a natural or anthropogenic or both.