Hydrochemistry and mercury cycling in a High Arctic watershed

Mass budgets for total mercury, major ions and nutrients were calculated for Amituk Lake, located on Cornwallis Island, Nunavut, Canada. Total mercury in two distinct snowpacks averaged 1.25 and 4.21 ng L 1; the discharge-weighted concentration of influent streams averaged 0.76 ng L 1. The recent and pre-industrial HgT fluxes in atmospheric deposition to the catchment were estimated to be 0.57 and 0.23 Ag m 2 but through retention within the catchment and/or re-volatilization from the melting snowpack, these decreased by 69% in the lake inflow. The spring freshet was the prime conduit for transporting HgT into Amituk Lake. Because of limited mixing of surface runoff with the lake water column during snowmelt, 59% of the HgT input was directly discharged through the outflow, 16% entered the lake water column where concentrations increased from 0.23 to 0.33 ng L 1 from June to August and 25% was deposited to the bottom sediments producing a sediment HgT flux of 3.1 Ag m 2.