Magnetic Susceptibility Mapping of Fly Ash in Soil Samples Near a Coal-Burning Power Plant in Pointe Coupee Parish, Louisiana

Magnetic susceptibility is a property that can be used to effectively determine the compositional changes of mineral materials in soil. The objective of this study is to detect the presence of magnetic particles related to the migration of fly ash from a nearby coal-burning power plant over parts of Pointe Coupee Parish, LA. This is based on the idea that the fly ash that is released into the atmosphere during the coal burning process contains heavy metals and magnetic particles in the form of ferrospheres, which can be used to trace back to the source. Maps of the top and sub soil were generated to differentiate the magnetic susceptibility values of the heavy metals potentially attributed to the migration and settling of fly ash onto the surface from any pre-existing or naturally occurring heavy metals in the sub soil. A 60 km2 area in Pointe Coupee Parish was investigated in approximately 0.5 km2 subsets. At each site, a minimum of 20 magnetic susceptibility measurements were obtained using a field probe along with discrete surface and subsurface samples collected for subsequent laboratory analysis. Samples of fly ash obtained directly from the source were also analyzed to verify the field and laboratory analysis. Contour maps representing the spatial distribution of the fly ash along with histograms of magnetic susceptibility values, reflective light microscope, and chemical analysis indicate a correlation between the proximity to the power plant and the predominant wind direction. Acquisition curves of the isothermal remanent magnetization demonstrate the presence of predominantly low coercivity minerals (magnetite) with a small amount of a high-coercivity phase. The microstructure of the magnetic fractions of the fly ash along with select top and sub soil samples were observed using a reflective light microscope for identifying and confirming the presence of ferrospheres associated with fly ash