The heavy metals like Ph, Hg, Cd, Cr, Cu, Zn, Mn, Ni, Ag, etc. of which As, Cd, Pb and Hg are considered biotoxin chemicals to humans, animals, fishes and environment Excessive concentrations of these heavy metals has been a matter of serious concern as they destabilize ecosystems because of their bioaccumulation in organisms, and toxic effects on biota and causing death in most living beings including wildlife. These heavy metals can enter into aquatic sources via drainage, atmosphere, soil erosion and all anthropogenic activities and get to the biogeochemical cycle which leads to biotoxicity due to bioaccumulation. The primary reasons of “Heavy metals toxicity is contamination of drinking-water (Pb pipes), high ambient air concentrations near emission sources, or from food chain or biogeochemical cycles Water and Fish samples were collected during the period March-April,2021 from the Tunia River which is a tributary of the Champamati River in the Bongaigaon district of Assam. The paper assessed the bioaccumulation of certain heavy metals in tissues of some freshwater fishes like Channa, Anabas, Puntius, Colisa and water sample of Tunia River, Bongaigaon district. Aquatic Absorption Spectrophotometric (AAS) analysis reveals the heavy metals concentration(mg/l) in water sample are Fe (3.1), Za (0.13),Cd(0.012) Pb(0.09),Ni(0.103) and in fish tissue sample Fe(9.1),Zu(2.51,Cd(0.2), Pb(2.2), Ni(1.0) The findings clearly establishes the deteriorated condition of the water quality at an alarming rate as sewage and effluents from the Bongaigaon refinery and petrochemical industry as well as from the entire Bongaigaon town are discharged into the Tunis River.
