The extent of metal transport in the stream draining from the tailings at the Nigadoo Mine, New Brunswick

Abstract

The Nigadoo Mine is located near Bathurst, New Brunswick. The mine is an abandoned Pb-Zn-Cu-Ag mine. Production at the site first occurred in 1956. Followed by repeated closures, the mine was permanently closed in 1977. During the operation of the mine, approximately 1. 9 million tons of tailings were generated. The New Brunswick government assumed responsibility for the site in 1986 after the mining company demonstrated evidence of a successful rehabilitation of the tailings. The state of the tailings has deteriorated since then. Investigations of the aqueous and sediment geochemistry combined with mass loading measurements were conducted to determine the extent of metal transport in the stream draining from the tailings. Mass loading measurements were unreliable and therefore could not be used for the purpose of this study. The presence of jarosite commonly associated with As was identified at the initial point of discharge. Further downstream the dominant forms of precipitates were Fe hydroxides and Mn oxides. The occurrence of Mn oxide is the result of the acceleration in the rate at which Mn is oxidized by an increase in dissolved oxygen from a converging stream. The storage of metals in the sediments such as Zn and Ni increased significantly with the precipitation of the Mn oxide. The associated metals are adsorbed or co-precipitated with the oxides.