Establishing a Vegetative Cap for Sustainable Stabilization of Copper Contaminated Soils in Torch Lake, Michigan

Extensive mining activities during the late 19th and early 20th centuries in the Upper Peninsula, Michigan have resulted in a number of contaminated sites with mine tailings. Several million metric tons of mine tailings were generated during the peak of copper (Cu) mining activities in this region. These tailings are called “stamp sands” because they were generated by crushing native Cu containing rocks, by a process known as stamping. The stamp sands were discharged into Lake Superior, other interior lakes and their shorelines, converting these areas into vast, fallow lands. The Cu contaminated stamp sands are being eroded back into the lakes, severely affecting the benthic community. The stamp sands are slightly alkaline in nature, have very low organic matter content and are highly deficient in nutrients, such as nitrogen, phosphorus and carbon. The Gay and Hubbell/Tamarack site stamp sand sites have about 50 and 19 times higher total Cu concentration compared to a normal agricultural soil, respectively. Biosolids collected from the local Portage Lake Water and Sewage Authority (PLWSA) and locally available compost was used as source of nutrients for the plants. The goal was to grow the oil seed crops camelina (Camelina sativa) and field pennycress (Thlaspi arvense) on these marginal lands, which can serve the dual purpose of producing feedstock for biofuels and reducing erosion of the Cu contaminated soils into the lakes. We conducted: i) laboratory incubation study to evaluate the geochemical fate of copper and soil nutrient profile in contaminated stamp sands with the addition of biosolids and compost amendments, ii) greenhouse column study to evaluate the effect of compost addition and plant cover (camelina, field pennycress) on the control of stamp sand erosion and fate and distribution of Cu, iii) field simulation study to evaluate the effect of plant cover (camelina, field pennycress) on control of stamp sand erosion and to evaluate the quality of biofuels from the biofuel feedstock (camelina, field pennycress) grown in stamp sands, and iv) door to door survey of the Torch Lake Township in Upper Peninsula of MI to get the opinions of local people about starting our project of reducing stamp sand erosion and biofuel feedstock production in the Torch Lake area. Results from this study will help in the (1) development of a novel technique for the establishment of a sustainable vegetative cap to prevent erosion of stamp sands into the Torch Lake which will serve as a model for the re-vegetation of other metal-impacted areas and (2) development of a novel biodiesel feedstock production system in marginal lands using oilseed crops, which is inexpensive, sustainable and regionally-appropriate