AN INVESTIGATION OF COMPOST AS A UNIQUE REMEDIATION TOOL FOR HEAVY METALS: A COMMUNITY INITIATED STUDY IN THE TAR CREEK WATERSHED, OTTAWA COUNTY, OK

Contaminated mining sites, such as Ottawa County, OK exist on an already complex network of biogeochemical processes that make it difficult to prioritize interventions that can reduce exposure. The Tar Creek Superfund Site, established in 1983, large mine waste (chat) piles and acid mine seepage continue to contaminate surrounding communities with zinc, lead, cadmium, and manganese. Locally sourced spent mushroom compost is currently used to remediate floodplain soils, prompting questions about potential risks/benefits of this unique shift in land use. This study was developed using a participatory approach. Through this study we aim to (1) better understand this unique use of compost for remediation, (2) continue research on the role of water and wind transport within the watershed to expand the EPA’s definition of OU5, and (3) to assess and communicate to community members benefits and risks of compost use in the floodplain.

Compost was collected by J&M farms, and consisted of samples used to grow mushrooms on the farm and from piles that are available for public use. We analyzed size-fractionated compost samples using non-destructive X-ray fluorescence methods and determined heavy metal concentrations (Pb, As, Mn, and Cd) known to be hazardous to human health to assess contamination from windborne chat. Three locations were chosen from compost piles, with average corrected concentrations of 3.7 μg/g (Pb), 0.8 μg/g (As), and 458 μg/g (Mn), compared to the geologic background of the area is 20 ± 1 µg/g (Pb), 1.5 ± 0.4μg/g (As), and 498 ± 1.2 μg/g(Mn). Nutrient analysis found that C:N:P for the compost was 29.7:1.9:1, compared to the BioComp (a commercially available compost standard, 30:1:1.08). We will also share results of a benchtop experiment simulating differing ratios of compost, and water sources to assess nutrient and metal loading as a result of compost use in the watershed.