Contaminant fate in high arctic lakes: development and application of a mass balance model

Steady- and unsteady-state models based on the QWASI fugacity/aquivalence approach and describing chemical fate in high Arctic lakes were developed and applied to Amituk and Char Lakes on Cornwallis Island, NWT, Canada. The model considered characteristics of Arctic lakes, such as water and chemical throughflow, development and depletion of ice cover, and temperature dependence of physical-chemical properties. The model of Char Lake was parameterized and calibrated with literature data for phosphorus, and for Amituk Lake, data were obtained from the Amituk Lake project, focusing on ΣDDT. Model results indicate that Arctic lakes act as conduits, not sinks for chemicals. Most loadings are from snowmelt that enter via stream inflow and most is exported from the lake; minimal amounts of chemicals volatilize or are retained in sediments. Burial is restricted by low-suspended particle concentrations that convey chemicals to the sediment. An attendant implication of the low-suspended particle concentrations is that nearly all chemicals remain in the dissolved phase in the water column. Consequently, chemical persistence is mainly controlled by water retention time which, for these small lakes, is several years. The illustrative unsteady-state model shows seasonal effects on chemical processes such as cryoconcentration that may increase water column concentrations by up to 15% in early May.