Measurement of Magnetic Particle Concentrations in Wildfire Ash via Compact NMR

Wildfire ash plumes deposit magnetic particles (nanoscale and larger) into rivers and streams. Post-fire runoff contains increased levels of suspended particles and contaminants; including traces of metals, nutrients, and total suspended solids that affect the water quality and aquatic species. This work reports on a compact and portable Nuclear Magnetic Resonance (NMR) system capable of measuring the magnetic particle content in wildfire ash. The system is comprised of a custom NMR device with a specially designed permanent magnet that shapes the magnetic field to provide the basis of a compact and robust NMR-based sensing system for the future in-field measurements of ash in aqueous solutions. The system is set up to measure transverse relaxation processes and can acquire sufficient data in as little as two minutes. Experimental results confirmed the linear relationship between magnetic content in water and transverse relaxation rates, and can therefore be used as a method for estimating magnetic content in wildfire ash.