CONTAMINANT FATE IN HIGH ARCTIC LAKES - DEVELOPMENT AND APPLICATION OF A MASS-BALANCE MODEL

Steady- and unsteady-state models based on the QWASI fugacity/aquivale nce approach and describing chemical fate in high Arctic lakes were de veloped and applied to Amituk and Char Lakes on Cornwallis Island, NWT , Canada. The model considered characteristics of Arctic lakes, such a s water and chemical throughflow, development and depletion of ice cov er, and temperature dependence of physical-chemical properties. The mo del of Char Lake was parameterized and calibrated with literature data for phosphorus, and for Amituk Lake, data were obtained from the Amit uk Lake project, focusing on Sigma DDT. Model results indicate that Ar ctic 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 s ediments. Burial is restricted by low-suspended particle concentration s that convey chemicals to the sediment. An attendant implication of t he low-suspended particle concentrations is that nearly all chemicals remain in the dissolved phase in the water column. Consequently, chemi cal persistence is mainly controlled by water retention time which, fo r these small lakes, is several years. The illustrative unsteady-state model shows seasonal effects on chemical processes such as cryoconcen tration that may increase water column concentrations by up to 15% in early May. (C) 1997 Elsevier Science B.V.