Rubidium measured by XRF as a predictor of soil particle size in limestone and siliceous parent materials

Abstract

Purpose Information about particle size distribution (PSD) and soil texture is essential for understanding soil drainage, porosity, nutrient availability, and trafficability. The sieve-pipette/gravimetric method traditionally used for particle size analysis is labour-intensive and resource-intensive. X-ray fluorescence (XRF) spectrometry may provide a rapid alternative. The study’s aim was to examine the use of XRF for rapid determination of PSD in Irish soils. Methods Soils (n = 355) from existing archives in Ireland were analysed with a benchtop energy-dispersive XRF (EDXRF). Correlation and regression analyses were determined to compare Rb, Fe, Al, and Si concentrations to % clay, % silt, and % sand. Also, linear regression models were developed to compare % clay, % sand, and % silt measured by the gravimetric method to values predicted by EDXRF. Results The relationship between element concentration and PSD was dependent on parent material. Rb, Al, and Fe showed a significant (p < 0.05) correlation (r > 0.50) with % clay and % sand in soils derived from limestone and siliceous stone parent materials. Rb was the best predictor for % clay (R2 = 0.49, RMSE = 10.20) in soils derived from limestone and siliceous stone-derived soils. Conclusion Geochemistry and clay mineralogy of the soils’ parent material strongly influenced the EDXRF’s ability to predict particle size. The EDXRF could predict % clay in soils from parent materials which weather easily, but the opposite was true for soils with parent material recalcitrant to weathering. In conclusion, this study has shown that the EDXRF can screen % clay in soils derived from limestone and siliceous stone parent materials.

The role of geoarchaeology in the interpretation of fragmented buildings and occupation surfaces: The case of coastal settlements in northeast Scotland

“…PC2 accounted for 7.29% of the total variance and demonstrated high loadings (>0.71) for pH and Rb. PC3 accounted for 6.29% of the total variance and presented moderate positive loadings (>0.45) for Rb and K. These elements are known to be strongly correlated in soils, and both PC2 and PC3 are likely to reflect lithogenic signatures (Croffie et al, 2022, p. 819). Across all three PCs, EC showed a negative correlation with pH, indicating that areas with a higher concentration of soluble salts or nutrients were generally more acidic.…”

The Vital Roles of Parent Material in Driving Soil Substrates and Heavy Metals Availability in Arid Alkaline Regions: A Case Study from Egypt

“…Sandy soils are sensitive to slumping, mainly when there is a deficiency in organic matter [58]. More siliceous parent materials, such as illite and kaolinite, create clay minerals with a lower CEC than less siliceous parent materials, such as montmorillonite and vermiculite [59]; therefore, boosting the clay fraction's content could benefit SOC stocks in two different ways, thus playing a relatively greater role in the CEC [60]. Moreover, the predominance of quartz for soils inherent from aeolian and marine deposits would facilitate leaching due to its low surface area and charges [61].…”