ScholarWorks at University of Montana

Remediation and restoration of the Upper Clark Fork River: influences on floodplain soil organic matter

Remediation and restoration of the Upper Clark Fork River (UCFR) represents an experiment addressing aquatic-terrestrial interaction at the landscape scale. Remediation and restoration along Reach A (from Warm Springs to Garrison) is designed to reconnect the channel and floodplain over ca. 70 km of river length. The process includes removal of metal-contaminated floodplain soils, lowering of the soil surface, introduction of new top soil, and re-vegetating the floodplain. Lowering the floodplain elevation should enhance river-floodplain interaction with potential influences on sediment deposition, and soil organic matter content and composition. In this study, we compared characteristics of soil organic matter, including % organic matter, water soluble dissolved organic carbon, and specific ultraviolet absorbance (SUVA) signatures among five sites associated with restoration of Reach A. The five sites were chosen to represent different soil types and ‘stages’ in the restoration process including: 1) pre-restoration conditions, 2) ongoing soil removal, 3) replacement top soil, 4) recently remediated and restored (i.e., <1>yr), and 5) 5-yr post-remediation floodplain soils. Measures of organic matter abundance and composition (i.e., SUVA) were compared to autochthonous organic matter (i.e., benthic algae, Cladophora) to assess how potential organic matter sources may differ in terms of bioavailable carbon for river foodwebs.