BIOACCESSIBLE PB IN BURLINGTON (VT) SOILS: FIELD AND MICROSCALE CONTROLS

The potential of a soil to immobilize heavy metal ions is dependent on the presence of adsorption sites, and the stability of its species over a wide range of geochemical conditions. Lead (Pb) is a cumulative toxin that affects many urban landscapes due to historical use of Pb-based paint and Pb gasoline. Because in-situ remediation of Pb is possible if the bioavailable fraction is rendered inert, understanding Pb-sorbent interactions is necessary to accurately and efficiently alter Pb speciation in soils. This multiscale research investigates Pb distribution at the field scale (in Burlington, VT), and speciation change at the microscale. The objectives of this study are to 1) determine efficient ways to predict Pb impacts on a community, and 2) characterize microscale controls on Pb speciation.

The field-scale study has shown that the relationship between total Pb and bioaccessible Pb is, unlike generally assumed, not consistent. Microscale investigations have so far determined that there is a positive correlation between the density of reactive microenvironments and the release of Pb from contaminated soil, and that altered distributions of microenvironments significantly alters the rate of release. The combination of geospatial and analytical tools used across a variety of scales provides the first multiscale analysis of microenvironments impact on Pb speciation in soils. Results of this research highlights the need to apply “community-scale” assessment of Pb soil contamination for efficient remediation.