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Free Flow Chemistry Helps Protect Wildlife

At the Seventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds, organized and presented by Battelle, the technical paper "Effectiveness of Soil Amendments for Reducing Exposure to Wildlife from Lead and Other Heavy Metals" will be presented.

The findings presented therein demonstrate how Free Flow chemistry, when used in heavy metals contaminated soils, can help to protect wildlife.

(ABSTRACT)

Effectiveness of Soil Amendments for Reducing Exposure to Wildlife from Lead and Other Heavy Metals

Will Gala and Carol Baker (Chevron Energy Technology Company, Richmond, CA, USA)

Daniel Oberle and Anthony Zapp (Stantec Consulting, Sylvania, OH, USA)

Heavy metals in soil can present an unacceptable ecological risk to wildlife through exposure pathways that include the ingestion of soil invertebrates (e.g., earthworms). At a former refinery site in the Midwest, a baseline ecological risk assessment indicated the potential for unacceptable risks to wildlife associated with ingestion of soil invertebrates that accumulated heavy metals (primarily lead) from contaminated soil. As part of bench-scale feasibility studies, the use of soil amendments to reduce the bioavailability of heavy metals in soil was investigated. Soil amendments evaluated included Class A biosolids or composted cow manure, ferrous sulfate, red mud, and Free-Flow® buffered calcium phosphates. The soil amendments were tested singly, and in combination, on 4 soil samples representing a range of metal concentrations. Their effectiveness for reducing metal bioavailability was evaluated using a modified Relative Bioavailability Leach Procedure (RBALP) to represent the mildly acidic conditions expected in the gut of the earthworm. On selected amendments and amendment combinations, 28-day earthworm (Eisenia fetida) bioaccumulation bioassays (ASTM E 1676-04) were also conducted.

Ferrous sulfate and Free-Flow® singly and in combination (and in combination with manure) were the most effective in reducing lead availability as measured by RBALP. Similar results were observed in the earthworm bioaccumulation bioassay with lead concentrations in the earthworm tissues reduced by as much as 70-80% depending on the amendment and soil lead concentration. Reductions in arsenic and zinc bioaccumulation were also noted, but to a lesser extent than the other metals. Analyses by X-ray absorption spectroscopy (XAS) of the amended soils indicated that reduction in earthworm bioaccumulation was largely associated with geochemical reactions which fixated the metals onto the oxide surfaces of manganese and phosphate minerals.