Seasonal changes in arsenic dynamics in a contaminated lake in eastern Ontario

Chemical dynamics in lakes, including remobilization of contaminated sediments, are subject to seasonal changes in a range of variables. Studies of arsenic dynamics in a small, contaminated lake in eastern Ontario, namely Moira Lake, have been conducted to examine these changes. Results have indicated that arsenic partitioning between sorbed and dissolved phases in the water column vary by over an order of magnitude with the highest values calculated during winter. This seasonality may be due to variations in suspended particle concentration, e.g., the particle concentration effect. The bulk of arsenic flux to the sediment, as measured by sediment traps, was comprised of resuspended particles, except during summer stratification. These, and other fluctuations, such as arsenic loading, were integrated into an unsteady-state mass balance model based on equivalence as an equilibrium criterion. The results of this model are compared with those of a steady-state simulation of average, annual conditions in order to estimate arsenic export from contaminated sediments.