TRACKING PEDOGENETIC PROCESSES AND HEAVY METAL CONTAMINATION IN SOILS USING COMBINED MAGNETIC PROPERTIES AND PXRF: A PRELIMINARY INVESTIGATION OF LOUISIANA SOILS

Pedogenetic processes have long been known to affect the magnetic properties of soils. Conversely, contamination of soils by heavy metals (e.g., Cu, Pb, Zn, and Cr) should not primarily result in major changes in magnetic properties because these elements are characterized by low Bohr magnetons. Here we empirically investigate soils' heavy metal concentration and magnetic properties to evaluate potential correlations. We use an array of magnetic properties, including low field magnetic susceptibility, magnetic remanence, and high field properties, as well as chemical element concentrations determined with pXRF. While previous studies demonstrated a link between magnetic susceptibility and the concentration of heavy metal elements, the pedogenetic processes responsible for such correlations remain unclear. Eighteen samples from three soil series (Dundee, Gallion, Memphis) were analyzed for Natural Remanent Magnetization (NRM) using a spinner magnetometer, low-field magnetic susceptibility (Klf) – with a Kappabridge KLY4, Magnetic Saturation (Ms), Magnetic Remanent Saturation (Mr), Coercitive Force (Hc), and Coercivity of Remanence (Hcr) - with a vibrating sample magnetometer. The results from the Dundee and Gallion sites had magnetic properties, which correlated with a more significant contribution of paramagnetic materials relative to ferromagnetic. The increased magnetic coercivity without a corresponding magnetic saturation increase may indicate titanium inclusions for Gallion. With its much higher magnetic saturation, Memphis correlated strongly with ferromagnetic minerals such as magnetite or hematite. This work on the natural properties of Louisiana soils will be a baseline for future studies on understanding anthropogenic pollution load and the re-distribution of metals under extreme weather events.