Researchers recently reported the results of an evaluation of a handheld X-ray fluorescence (XRF) device as a field screening tool for soil mercury as part of on-going remedial investigations along the South River in Waynesboro, Virginia. As reported by the research team, the method achieved a detection limit of 7.4 mg/kg Hg with a 60-s analysis time, which improves upon earlier attempts and is sufficient for detecting mercury at generic risk assessment soil screening levels (23 mg/kg Hg). The study also demonstrated levels of accuracy and precision for the method that rivaled traditional laboratory methods. In a split-sample comparison with laboratory Method 7471A, field XRF results agreed with an R2 of 0.93 and a median coefficient of variation of 15%. Precision estimates from duplicate and triplicate samples were not statistically different between the two methods and were constrained by sample heterogeneity rather than by method capabilities.
The study demonstrated that handheld XRF can be successfully used at contaminated sites to achieve high quality Hg results that are accurate, precise, and at a level of sensitivity commensurate with generic risk assessment screening levels.