While atmospheric mercury deposition is ultimately the main source of mercury to most freshwaters, many rivers and lakes receive most of their mercury loads from atmospheric deposition that first passes through terrestrial systems.

Reed Harris Environmental Ltd., in conjunction with the US Geological Survey, has developed a simple model of mercury inputs and outputs from terrestrial soil systems to provide a screening level assessment of the potential delays imposed by terrestrial systems on the delivery of mercury to freshwaters.

Initial results suggest long delays in the response of terrestrial mercury export following changes in mercury deposition, on the order of decades or centuries.