The role of the atmosphere in great lakes contamination

Certain implications are discussed of the data in a recent report of atmospheric deposition rates to the Great Lakes by Hoff et al. (Atmospheric Environment 30, 3505–3527, 1996). An analysis of the data suggests that for many persistent, volatile organic chemicals concentrations in water are close to a state of long term (several years, within a factor of approximately five) equilibrium with the atmosphere, but are in a constant state of short-term seasonal adjustment. Under these near-equilibrium conditions the actual magnitude of air to water loadings become relatively unimportant as determinants of lake ecosystem contamination, and the significance of land-based loadings is reduced. Success in decontaminating or restoring the Great Lakes is becoming increasingly dependent on atmospheric concentrations and thus on the processes which determine these concentrations.