Peculiarities in quantification of airborne particulate matter by means of Total Reflection X-ray Fluorescence

TL;DR

This paper discusses the use of Total Reflection X-ray Fluorescence (TXRF) for elemental analysis of airborne particulate matter, emphasizing the importance of understanding its limitations and validation methods for accurate environmental and climate research.

Contribution

It introduces a self-consistent quantification method using grazing incidence X-ray fluorescence to validate TXRF measurements of airborne particulate matter.

Findings

GIXRF can validate TXRF elemental quantification.

Methodology enables reliable, element-sensitive PM analysis.

Approach adaptable to tabletop instrumentation.

Abstract

Knowledge on the temporal and size distribution of particulate matter (PM) in air as well as on its elemental composition is a key information for source appointment, for the investigation of their influence on environmental processes and for providing valid data for climate models. A prerequisite is that size fractionated sampling times of few hours must be achieved such that anthropogenic and natural emissions can be correctly identified. While cascade impactors allow for time- and size-resolved collection of airborne PM, total reflection X-ray fluorescence (TXRF) allows for element-sensitive investigation of low sample amounts thanks to its detection sensitivity. However, during quantification by means of TXRF it is crucial to be aware of the limits of TXRF in order to identify situations where collection times or pollution levels were exceedingly long or high. It will be shown by means of grazing incidence X-ray fluorescence (GIXRF), where different reflection conditions are probed, that a self consistent quantification of elemental mass depositions can be performed in order to validate or identify issues in quantification by means of TXRF. Furthermore, monitors of validity for a reliable quantification of the elemental composition of PM by means of TXRF will be introduced. The methodological approach presented can be transferred to tabletop instrumentation in order to guarantee a reliable quantification on an element sensitive basis of the PM collected. This aspect is highly relevant for defining appropriate legislation and measures for health and climate protection and for supporting their enforcement and monitoring.