Water Resources Research Act Program

Details for Project ID 2003ID11B

Validating Meta(loid) Flux Predicitons from Lake Coeur d'Alene Sediments Using Contaminated Ponds as Mesocosms

Institute: Idaho
Year Established: 2004 Start Date: 2004-03-01 End Date: 2005-02-28
Total Federal Funds: $14,781 Total Non-Federal Funds: $34,079

Principal Investigators: Matthew Morra, Daniel Strawn

Project Summary: Lake Coeur d'Alene (CDA) in Idaho is the second largest natural lake in the Inland Northwest, provides drinking water for at least five communities, and serves as a primary recreational area. Unfortunately, Lake CDA is also a major collecting bed for contaminated sediments produced during mining and ore processing activities. The USGS has estimated that as much as 85% of the lake bottom is contaminated with metal(loids) such as Cd, Zn, Pb, and As. It is feared that continued development within the region will alter lake nutrient status leading to eutrophication and the promotion of trace element release from the sediments. Unfortunately, projections of metal(loid) release are based on controversial model assumptions about the sediments which may not accurately describe geochemical principles controlling metal sequestration. Our proposed research is focused on resolving the controversy by using small ponds to directly determine metal flux prior to the development of anoxic conditions and comparing this flux to that which occurs after the onset of anoxic conditions. Metal concentrations of sediment pore waters and metals in the overlying water will be determined under both aerobic and anaerobic conditions using equilibrium samplers (peepers) installed in the sediment of the ponds. These data will be compared to benthic flux model predictions, thereby allowing model validation. Reasons for any differences in the actual data and model output will be determined and used for model revision. We have performed the first season of sampling, obtaining data for the ponds when under anaerobic conditions. We are requesting a second year of funding to continue our project, thereby allowing for the accumulation of two years of data on which to run the model.