Design measurements around the investigation
The value of field screening starts with a sound sampling design. Mapping contamination, locating anomalies and checking excavation boundaries place different demands on representativeness and data quality. EPA Method 6200 addresses elemental measurements in soil and sediment using portable XRF and links their use to project data quality objectives. Before collecting readings, define the investigation purpose, target elements, sampling logic and situations requiring laboratory confirmation.
Keep sample condition attached to the result
Moisture, particle distribution, surface flatness and homogeneity can affect field results. In situ readings and results from dried, sieved or ground material should not be combined without explaining the preparation differences. Record coordinates, depth, surface condition, preparation steps and measurement conditions for each location. When stones, plant remains or isolated particles are present, document how they were handled instead of selecting only convenient surfaces.
Apply quality controls throughout a batch
We recommend specifying blanks, check materials, repeat measurements and laboratory comparisons in the project plan, together with acceptance criteria and actions when controls fail. EPA’s field procedures can inform the design, but their frequencies or limits should not be copied into a different project without justification. When repeat readings disagree, first investigate heterogeneity, contact conditions and contamination before attributing the problem to instrument drift. More repetitions alone do not remove bias.
Retain comparison samples for important decisions
Choose laboratory comparison samples across concentration ranges, soil types and locations important to the decision. Avoid selecting only samples likely to agree. Check units, dry or wet basis, sampling scale and methodological differences when comparing results, and document possible explanations for disagreement. Flag data collected while a control was failing and assess whether it needs to be repeated; do not silently remove anomalies from a later report.
A reviewable deliverable includes a sampling map, sample tracking records, field data, quality-control findings and follow-up explanations. XRF readings can support an investigation, but their suitability for a particular risk or engineering decision must be evaluated against project objectives and applicable requirements. An instrument result is not, by itself, a soil-risk conclusion.
References
Accessed: September 29, 2026. This article discusses methods and workflows. Apply the practical recommendations in conjunction with applicable standards, contractual requirements and local method validation.