Assessing Attenuation Effects in X-ray Fluorescence Analysis of Light Elements in Mineral Dust

Reliable elemental analysis is important for understanding mineral dust mass concentrations, composition, sources, and atmospheric processing. X-ray attenuation of light elements in widely used X-ray fluorescence (XRF) measurements can lead to underestimated dust mass and inaccurate dust composition, yet attenuation corrections are often neglected in ambient particulate matter (PM) analysis. This study experimentally quantifies attenuation for silicon and aluminum by comparing XRF and gravimetric measurements of samples with known compositions. Silica (SiO₂), alumina (Al₂O₃), and Arizona test dust (ATD) were aerosolized and collected on Teflon filters to generate samples with varying mass loadings and particle size ranges. Results validated that attenuation increases with both mass loading and particle size. Greater Si attenuation observed in ATD than in SiO₂ at equivalent mass loading and size range indicates that other crustal elements enhance Si attenuation. Theoretical models considering only mass loading or particle size underestimated the measured attenuation. We developed empirical equations to correct for Si and Al attenuation. Applying these equations, with a size scaling factor for nondust species, to ambient dust-dominated PM samples from the global Surface PARTiculate mAtter Network (SPARTAN) increased dust concentrations by 21% in PM_2.5 and 29% in PM₁₀. This work demonstrates the importance of considering attenuation effects in XRF analysis for accurate dust inference from measured elements.