Optimizing pXRF sample preparation for in situ soil screening: A regulatory framework perspective

Area of Science:

• Environmental Science
• Analytical Chemistry
• Geochemistry

Background:

• Urban soils are susceptible to trace metal contamination.
• Accurate assessment of soil contamination is crucial for public health and environmental protection.
• Portable X-ray fluorescence (pXRF) is a valuable tool for in-situ elemental analysis.

Purpose of the Study:

• To evaluate the influence of different sample preparation methods on pXRF measurements of trace metals in urban soils.
• To compare the accuracy and precision of wet, dry, and pelletized sample preparations against regulatory thresholds.
• To determine the optimal pXRF sample preparation strategy for urban soil contamination screening.

Main Methods:

• Comparison of pXRF measurements from wet, dry, and pelletized soil samples.
• Analysis of trace metal concentrations (e.g., lead) in urban soils from Hartford, CT.
• Statistical analysis of slope values to quantify preparation method impacts.
• Evaluation of missed regulatory exceedances for different preparation methods.

Main Results:

• Drying soil samples generally increases measured metal concentrations due to moisture removal.
• Pelletization slightly reduces measured concentrations but improves precision and minimizes variability.
• Wet in-situ analysis can underestimate metal concentrations, potentially missing regulatory exceedances for lead.
• Dry in-situ measurements offer a balance between practicality and accuracy, significantly reducing missed exceedances.

Conclusions:

• Sample preparation methods critically affect pXRF accuracy and precision for urban soil analysis.
• Dry in-situ preparation is recommended for screening to balance efficiency and reliability.
• Adapting pXRF preparation techniques to specific regulatory and site contexts is essential for effective contamination assessment.