Naturally elevated spring-time fluxes of zinc and other elements from a sulphide ore deposit area in Citronen Fjord, North Greenland (83°N)

Prior to planned mining activities near Citronen Fjord in North Greenland, the natural concentrations and fluxes of zinc (Zn) and other elements were studied in a local river during 1994, 1995 and 2010. The river runs through a weathered, naturally exposed part of a large sulphide ore deposit (a so-called gossan), which consists mainly of sphalerite (ZnS), pyrite (FeS2) and to a lesser extent galena (PbS). Water samples were taken daily and analysed for total metal contents (dissolved and loosely particle-bound metals) and sulfur (S). The river discharges were measured throughout the 3-month summer periods. In all years, high concentrations of Zn and other metals including iron (Fe) and lead (Pb) were found in the river water in the weeks after thaw (up to 3,700 μg Zn L− 1, 4,000 μg Fe L− 1 and 21 μg Pb L− 1). Later in the summer, concentrations of these metals decreased to typically 1–10 μg Zn L− 1, 10–100 μg Fe L− 1 and 0.05–0.5 μg Pb L− 1. In 2010, 89%, 41% and 68% of the total annual fluxes of Zn (1.1 t), Fe (1.5 t) and Pb (7 kg) in the river were observed within the first three weeks after thaw. In contrast, only 12% of the water flow occurred during this period. This indicates that a significant generation and accumulation of weathering products from sulphide oxidation, including Zn, Fe and Pb, takes place in the upper exposed part of the gossan during dry periods in the summer or during winter, which is flushed out with the first melt water. Also, it shows the importance of including early spring-time water sampling when evaluating runoff/river chemistry in Arctic areas.

► The natural release of Zn was studied in a river during 3 summer seasons.
► Highest Zn concentrations were observed within 1–2 weeks after thaw.
► More than 80% of the annual Zn release occurred within 3 weeks after thaw.
► In contrast, < 20% of the water discharge occurred during this 3-week period
► A spring-flush of winter-generated products from sulphide oxidation is indicated.