Soil Characterization Using Gamma-Ray Spectrometry: Caste study in Petzenkirchen, Austria

Soil physical and chemical parameters—such as texture, density, water content, total organic carbon (TOC), and total nitrogen (TN)—are typically measured at a single point and then extrapolated to represent a larger area. To accurately characterize these areas, a substantial number of samples must be collected, which can lead to high laboratory costs. Using a UAV-borne gamma-ray spectrometer at relatively low altitudes allows for collecting high-resolution spatial information on radionuclides. This information may subsequently be used to derive soil physical and chemical parameters.

In the Hydrological Open-Air Laboratory (HOAL) in Petzenkirchen, Lower Austria, a Medusa gamma-ray MS-1000 was employed to test the potential of obtaining continuous soil information on basic soil properties. The gamma-ray spectrometer was mounted on an Acecore NOA UAV and a backpack, enabling users to remotely fly or walk across the area of interest, respectively. The study focused on three land-use types: agricultural land – covered by winter wheat in an early development stage, 3-year-old grassland, and 10+ year-old grassland, each with an area of about 0.2 hectares. The soil in this area is classified as drained typical gley and a gleyic colluvisol. After surveying with the gamma-ray spectrometer from each land-use type, we randomly collected 10 soil samples and analyzed for texture, density, water content, TOC, and TN.

Previous research by Van der Veeke et al. (2021) and Taylor et al. (2023) provides some contradictory context to this experiment. Van der Veeke et al. (2021) achieved R² values greater than 0.8 for clay and sand content compared to measured soil data. In contrast, Taylor et al. (2023) obtained correlation coefficients ranging from -0.59 to 0.61 but received better values of about -0.71 or lower for soil moisture, total carbon and TN. This study aims to offer a more definitive conclusion in predicting soil physical and chemical parameters using gamma-ray spectrometry.