Long-term performance of removal actions will depend on accurate delineation of contaminated media in relation to risk-based action levels. Field portable X-ray fluorescence (FPXRF) was identified as a potential analytical method to identify areas of contaminated soils and sediment. Rapid identification of areas exceeding action levels would improve long-term performance of removal actions, expedite construction activities, and optimize removal action expenditures.
The efficacy of FPXRF technology has been established in many applications. FPXRF is subject, however, to potential site-specific interferences, and published FPXRF detection limits are close to risk-based action levels. Therefore, a demonstration of methods applicability (DMA) analysis was completed prior to implementing FPXRF. The DMA analysis is a site-specific statistical evaluation of FPXRF performance in relation to standard laboratory methods.
The DMA evaluation shows that FPXRF is adequate for definitive analyses of lead and zinc, but inadequate for arsenic, cadmium, copper, or mercury. Fortunately, the DMA indicates that these metals are co-located with lead and zinc, therefore, identification of media exceeding lead and zinc action levels also identifies media exceeding arsenic, cadmium, copper, and mercury action levels. Implementation of FPXRF at the site will utilize field-based action levels for lead and zinc, and sample preparation protocol defined in the DMA. This lowers risks associated with potential site-specific FPXRF interferences, while providing rapid identification of media exceeding risk-based action levels.