EFFECTS OF BIOSOLIDS AND COMPOST AMENDMENT ON GEOCHEMICAL FORMS OF COPPER AND PHOSPHORUS IN THE CONTAMINATED STAMP SANDS OF TORCH LAKE, MICHIGAN: AN INCUBATION STUDY

Extensive copper (Cu) mining activities during the last two centuries in the Upper Peninsula of Michigan have resulted in several million metric tons of stamp sands being generated, and subsequently discharged into Lake Superior and its offshoots, such as Torch Lake. To reduce the exposure of Cu toxicity to aquatic organisms in the lakes, the sediments were dredged and dumped on the lakes’ shorelines, thereby converting these areas into vast, fallow lands which are not conducive to plant growth. The stamp sands are now being eroded back into the lakes, severely affecting the benthic community. Our goal is to grow oil seed crops camelina (Camelina sativa), field pennycress (Thlaspi arvense) on these marginal lands, which will serve the dual purpose of producing feedstock for biofuels and also reduce the erosion of Cu-contaminated soils into the lakes. We will provide plant nutrients through the application of locally-generated biosolids and compost instead of commercially available fertilizers. Here, we report a laboratory incubation study investigating the effects of biosolids and compost addition on the geochemical forms of Cu and phosphorus (P) in stamp sands collected from Hubbell/Tamarack site in Torch Lake, MI. Biosolids and compost are added at rates of 0, 25, 50, 100 and 200g/kg, and incubated in polyethylene bags at 70% water holding capacity. Soil samples are collected on 0, 15, 30 and 60 days, and analyzed for pH, salinity, organic matter, total Cu and P, phytoavailable Cu and P, and sequentially extracted geochemical forms of Cu and P. Addition of biosolids and compost at lower rates (25 and 50g/kg stamp sand) increased the carbonate bound fraction of Cu after 15 days. Experimental work is ongoing to determine the effects of biosolids and compost addition for a longer period of time (30 and 60 days) on geochemical forms of Cu and P. Data obtained from this incubation study will help optimize the experimental conditions for the upcoming greenhouse and field studies.