GEOCHEMICAL FORMS OF COPPER AND PHOSPHORUS IN COPPER-MINING IMPACTED SEDIMENTS OF UPPER PENINSULA, MICHIGAN

Several million metric tons of stamp sands were generated in the Upper Peninsula of Michigan during extensive copper (Cu) mining activities in the late 19^th and early 20^th century. These stamp sands, containing primarily Cu, were discharged into various offshoots of Lake Superior. Given the lack of tolerance of Cu toxicity of aquatic organisms, in due course, the sediments were dredged and dumped on the lake shorelines, converting these areas into vast, fallow lands that are not conducive to plant growth. Erosion of these Cu-contaminated stamp sands back to the lakes is severely affecting the benthic community. To solve this problem, we plan to grow hardy, cold-tolerant oil seed crops camelina (Camelina sativa) and field pennycress (Thlaspi arvense) on these marginal lands, aided by a plant growth promoting bacteria that we isolated from the stamp sands. This will serve the dual purpose of producing feedstock for biofuels, and also providing a vegetative cap, thus reducing the erosion of stamp sands into the lakes. We intend to make this a complete "green" venture, proving plant nutrients via application of locally-generated biosolids instead of commercially available fertilizers. Here we report a laboratory incubation study, in which we are investigating the effects of biosolids application on the speciation of copper (Cu) and phosphorus (P) in stamp sands collected from Gay site and Hubbell/Tamarack site in Torch Lake, MI. Biosolids are added at agronomic rates: 0 (control), 80, 160 and 320 mg to 100 g of stamp sands, and the mixtures are incubated in polyethylene bags. A 70% water holding capacity is maintained in the stamp sand-biosolids mixtures throughout the experiment. Soil samples are collected periodically after 0, 15, 30 and 60 days, and analyzed for pH, salinity, organic matter, total organic carbon, total Cu and P, potentially phtytoavailable P and Cu, and sequentially extracted, operationally-defined geochemical forms of P and Cu. Data obtained from these experiments will help optimize the operational variables for the follow-up greenhouse and field studies.