31-10 Magnetic Properties Identify Heavy Metal Contamination at Pig’s Eye Park, St. Paul, Minnesota

Session: Environmental Geochemistry and Health (Posters)

Poster Booth No.: 36

Presenting Author:

Angelina Regan

Authors:

Regan, Angelina Michaela¹, Pinto, Stella Grace², Feinberg, Joshua M.³, Snell-Rood, Emilie C.⁴, Jelinski, Nicolas A.⁵, Penn, R. Lee⁶

(1) Manchester, CA, USA, (2) Hanover, NH, , (3) University of Minnesota, Minneapolis, MN, USA, (4) University of Minnesota, Minneapolis, MN, USA, (5) University of Minnesota, Minneapolis, MN, USA, (6) University of Minnesota, Minneapolis, MN, USA,

Abstract:

Methods for characterizing heavy metal contamination in soils are often costly and time-consuming, which impedes efficient widespread monitoring. The objective of this study is to evaluate the use of magnetic susceptibility as a proxy for heavy metal content to assess the extent of contamination at our study area: Pig’s Eye Park in St. Paul, Minnesota. Previous studies have attempted to use magnetic susceptibility as an environmental monitoring tool, but ambiguities can arise if various inputs are not well understood beforehand. If this method can be calibrated to the needs of individual sites, then it can reduce costs and sample processing time and be a less destructive method for future contamination studies. Pig’s Eye Park is located on the floodplain of the Mississippi River, where it served for decades as a general landfill for the city of Saint Paul and a repository for sludge ash from the adjacent wastewater treatment plant. Consequently, the soils and groundwater at the site show high concentrations of heavy metals and other pollutants. Initial remediation efforts in the early 2000s involved the removal of the most hazardous materials and the installation of a clay cap to prevent subsequent contaminant transport, but widespread contamination still remains and site managers do not have a clear sense of where lead (Pb)-rich sludge ash is located. We collected 384 geospatially-tagged soil samples across the site and measured magnetic susceptibility at two different frequencies (300 A/m at 465 Hz and 4650 Hz). Each sample’s elemental composition was also measured using a portable X-Ray Fluorescence spectrometer. Comparing our in-phase susceptibility values against elemental concentrations revealed strong positive correlations (Spearman coefficients >0.7) with Pb, copper (Cu), tungsten (W), and zinc (Zn). There is also a strong positive correlation (Spearman >0.7) between the absolute frequency dependence and these elements, suggesting that finer grain sizes carry higher heavy metal concentrations. Electron microscopy reveals that this relationship is linked directly to the occurrence of wastewater sludge ash. Thus, handheld magnetic susceptibility meters can rapidly map the location of persistent heavy metal contamination at this site. With further validation of this method for heavy metal detection, this approach could become a standard tool for quick and cost-efficient contamination assessment at similarly impacted sites.

© Copyright 2026 The Geological Society of America (GSA), all rights reserved.