Water Resources Research Act Program

Details for Project ID 2010MN269B

The role of sulfate reduction in sediment of the St. Louis River estuary

Institute: Minnesota
Year Established: 2010 Start Date: 2010-07-01 End Date: 2011-07-01
Total Federal Funds: $30,000 Total Non-Federal Funds: $46,419

Principal Investigators: Nathan Johnson

Project Summary: A recent study by the Minnesota DNR has confirmed that sulfate concentrations are elevated in the St. Louis River as a result of mining activities in the watershed. Sulfate concentrations are diluted downstream of tributaries draining mining-impacted watersheds, but sulfate in the lower river (within 30-50 miles of Lake Superior) are still significantly higher than unimpacted streams in the area. Although this previous study provided much information about sulfate in the St. Louis River, little is known about the role sulfate plays in key biogeochemical processes in the sediment of the river or estuary. The objective of this study is to investigate the role that sulfate plays in driving contaminant-related bacterial processes in the surficial sediment of the St. Louis Estuary. The motivation comes from the contaminant transformation processes that sulfate reduction is involved in, including mercury methylation, heavy metal sequestration, and organic contaminant degradation. Using sediment cores and laboratory experiments, this project will characterize the location and extent of sulfate reduction in surficial sediment, or that sediment which may exchange contaminants with the overlying water. Results from this work will determine whether or not biological sulfate reduction is occurring at shallow depths in sediment of the St. Louis River Estuary. The estuary is designated an Area of Concern, and sediment is known to be contaminated with organic contaminants and mercury. The results of this study will help to determine the influence of mining-related sulfate loads on mercury methylation and other contaminant transformations in the estuary. This understanding could lead to more effective risk management strategies for sediments in the Area of Concern.