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In-Situ Lead Remediation in an Acidic Pine Barrens Wetland
Citation:
Noerpel, Matthew, A. Betts, A. Wade, Jenny Goetz, A. Schwarber, AND T. Luxton. In-Situ Lead Remediation in an Acidic Pine Barrens Wetland. SETAC 2022 North America 43rd Annual Meeting, Pittsburgh, PA, November 13 - 17, 2022.
Impact/Purpose:
The purpose of this presentation is to report on the effectiveness of several remedial strategies employed at the Burnt Fly Bog Superfund site. The soil amendments were applied with the goal of converting labile lead to a more insoluble form to varied success.
Description:
Lead remains a common and harmful contaminant at many Superfund and other contaminated waste sites. The Pine Barrens of New Jersey are a large pine forest which dominates the southern half of the state featuring sandy acidic soils. The current study site is located in the northern end of the Pine Barrens with sandy soil over top of a shallow poorly permeable clay layer creating a wetland environment. The site was contaminated with lead pre-1980 and is in the final stages of remediation. As part of the remedy, three separate soil amendment regimes were applied to small test plots in two different regions of the wetlands to assess the effectiveness of the amendments at controlling the mobility and solubility of lead. The first application was a reactive substrate that included biosolids and calcium sulfate addition added to induce the synthesis of galena. The second and third were Apatite II additions to induce the synthesis of pyromorphite. The Apatite II was added both as a surface applied amendment and mixed into the top 6 inches of soil. After approximately 20 and 26 months post application, at the end of the dry and wet seasons respectively, soil and porewater samples were collected and analyzed for a suite of geochemical parameters as well as lead concentration and speciation via X-ray absorption spectroscopy. The porewater data shows a modest decrease in the lead concentration in the areas with amendment applied as compared to the control areas, however the solid speciation results show limited success of the soil amendments in transforming the lead to the target species. Geochemical parameters such as pH, Eh, cations, anions and TOC were measured and trends with Pb concentration and speciation will be discussed. The reduction in porewater lead and the lack of a change in solid phase lead speciation is likely due in part to lime additions included with the amendments. The increase in sediment pH from the lime may increase lead adsorption on to mineral or organic surfaces. However, the effects from liming cannot be considered a permanent reduction due to the naturally acidic water in the Pine Barrens. This work also highlights the importance of sample handling when a speciation analysis will be performed. Samples collected open to the air and oven dried had a significantly different makeup than those maintained in an anoxic environment for the duration of the experiment.