EFFECTS OF COMPOST ADDITION AND PLANT COVER ON THE FATE AND DISTRIBUTION OF COPPER IN CONTAMINATED STAMP SANDS OF TORCH LAKE, 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 residual 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. We decided to grow hardy, cold-tolerant oil seed crops camelina (Camelina sativa) and field pennycress (Thlaspi arvense) to serve the dual purpose of producing feedstock for biofuels, and providing a vegetative cap, thus reducing the erosion of stamp sands back to the lakes. We made this a complete "green" venture, providing plant nutrients via compost instead of commercially available inorganic fertilizers. Here, we report a greenhouse column study investigating the effects of compost application and plant type, camelina and field pennycress, on the fate and distribution of Cu in the stamp sands collected from Hubbell/Tamarack site in Torch Lake, MI. The compost was added at rates of 0, 25, 50, 100 and 200g per kg of stamp sand. The experiment was done in triplicates, resulting in a total of 33 columns for 10 treatments and 1 control. Water was added to the columns according to each column’s water holding capacity and equilibrated for 10 days. Seeds of camelina and field pennycress were sowed. The plants germinated and grew in all the columns except in the control. Soil samples and leachates were collected at monthly intervals up to a period of six months. The soil samples were analyzed for total Cu, P, Al and Fe. The leachates were analyzed for turbidity, total suspended solids, total organic and inorganic carbon, dissolved and total Cu, P, Al and Fe. The seeds, shoots and roots of camelina and field pennycress have been harvested and are currently being analyzed for Cu.