TRANSPORT AND FATE OF MINE TAILINGS IN A COASTAL FJORD OF BRITISH-COLUMBIA AS INFERRED FROM THE SEDIMENT RECORD

Eight gravity cores collected from Alice Arm and Upper Observatory Inl et in British Columbia were analyzed for Pb-210 to determine the sedim ent accumulation rates. Sediment samples were also analyzed for Al, Ba , Cd, Cu, Fe, Mn, Pb, and Zn to establish the transport and fate of mi ne tailings in Alice Arm. Sediment accumulation rates ranged from 0.17 to 0.76 g cm(-2) per year in Upper Observatory Inlet; in Alice Arm th e accumulation rates ranged from 1.39 g cm(-2) per year near the sill to above 2 g cm(-2) per year in the upper sections of the arm. The sig nificantly lower sedimentation rates in Observatory Inlet suggest that much of the sediment and mine tailings entering Alice Arm are trapped within the arm. Elevated Cd, Pb and Zn concentrations in the cores ta ken from Alice Arm indicate the presence of tailings from an open-pit molybdenum mine at the head of the Arm (Kitsault). Ba, Fe and Mn incre ase deep in cores from the head of Alice Arm, and a maximum in the Ba concentration around 1956 in a core from near the sill are probably as sociated with tailings disposed earlier into the Kitsault River at the head of the inlet (Dolly Varden mines). Post-1900 increases, particul arly in Cu and Zn, for sediments from upper Observatory Inlet coincide with mining and smelting operations by Anyox at Granby Bay. Both the sediment accumulation rates and the sediment metal concentrations sugg est that Alice Arm is an effective trap for most of the tailings suppl ied to it. The application of Principal Component Analysis on the meta ls data set shows a remarkably clear separation between Alice Arm (Cd, Pb, Zn) and Observatory Inlet (Cu, Zn) sediments; it appears that the submarine tailings discharge used by the most recent mine at Kitsault (Amax) deposited most tailings near the outfall and down the centre o f the fjord.