PROSPECTING GEOCHEMICAL EFFECTS OF LANDUSE ON SOIL CHARACTERISTICS WITH PXRF

The utility and accuracy of hand-held portable x-ray fluorescence (pXRF) spectrometry for cost-saving analysis of point source polluted soils are well documented. However, changes to chemical composition that alter soil processes are not limited to high concentrations of pollutants. Landuse activities can impact the physical, biological and chemical processes of soils, which in turn affect the chemical composition of the soil and its ability to provide essential ecosystem services. Quantifying the geochemical effects of landuse activities on soil processes is fundamental for ensuring sustainable use of our soil resources. The most precise methods to quantify element concentrations in soil samples requires sample collection, transportation, and storage; dissolution of the soil sample with hazardous and costly chemicals; and expensive, specialized analytical equipment. High-resolution sampling across large areas and/or within multiple soil profiles can quickly become very costly. This study evaluates the efficacy of pXRF geochemical analysis for identification of targeted sample collection and geochemical analyses of soils impacted by landuse activities, but without point source pollution. Soil samples from three soil cores were analyzed by ICP-OES and ICP-MS at 2-4 centimeter intervals to a depth of 60 centimeters. A subset of these samples was selected for pXRF analysis to evaluate the instrument’s ability to identify interpretable differences and trends. The pXRF data for several elements were in good agreement with the higher precision data. However, not in agreement, some elements have concentrations that are near or below the limit of detection for pXRF, yet may still negatively affect plants and organisms, including humans. Therefore, additional means of targeting sampling density and locations are required to identify landuse effects on soils.