Hydrochemical Fluxes in a High Arctic Wetland Basin during Spring Snowmelt

Abstract

Hydrochemical transport within a small fen basin on Axel Heiberg Island, N.W.T., was examined during the 1990 spring melt. Snow cover, lake inflow, hillslope runoff, and basin outflow were monitored for pH, conductivity, and the storage and flux of five major ions (Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl⁻). Ca²⁺ dominated the ionic load in the premelt snowpack. Although there were substantial spatial and temporal variations in runoff, ion concentrations and export rates from the basin's slopes, transport of all ions tended to rise during periods of increased runoff. Runoff became depleted in H⁺ and enriched in the remaining ions to varying degrees as meltwater interacted with basin soils. H⁺ was retained on hillslopes, while there was net export of Ca²⁺, Mg²⁺, Na⁺, K⁺, and Cl⁻ to the fen. Differences in active layer thickness within the basin appeared to have an important control on the contact time between infiltrating meltwater and the soil; these differences in turn accounted for spatial variations in net ionic export from the hillslopes. The snowpack represented 51% of the total water input to the basin; however, snow cover made only a minor contribution to total ionic inputs. H⁺, Na⁺, K⁺, and Cl⁻ were retained in the wetland, while there was net export of Ca²⁺ and Mg²⁺ from the basin. Weathering and cation exchange between H⁺-rich meltwater and alkaline soils were likely responsible for the release of Ca²⁺ and Mg²⁺ to surface runoff.