XRF Analysis of Strontium in Drywall and Effects of Drywall Finish on Strontium Measurement

摘要

Some United States homes built or renovated between 2003 and 2008 contain drywall imported from China. Some of these homeowners have reported concerns including sulfur-type malodors and the occurrence of black corrosion (copper sulfidation) of electrical, plumbing, HVAC, and refrigeration components in the structure. A handheld XRF Spectrometer (Innov-X Alpha XRF, Model No. ? -4000) was used to make in situ direct measurement of elemental strontium in drywall. To evaluate the attenuation effect of the surface coatings (e.g., paint or textured finish) on the XFR measured strontium concentration, each sample was measured in three planes: front, back, and cut edge (i.e., exposed gypsum core). Statistical comparisons were made on 25 paired samples. The difference between the median strontium concentrations measured through the front (painted texture finish) and back (paper faced), and the median concentrations measured through the back and cut edge were statistically significant (p<0.001). The type of drywall finish has a significant effect on the accuracy of the strontium measurements when measured by a handheld XRF analyzer through the drywall finish. The strontium concentration measured through the finished surface of the drywall should be adjusted using a site-specific correction factor to prevent underestimating the true concentration due to attenuation by the surface finish and thus reaching a false-negative conclusion. Screening of drywall for strontium with an XRF is a reliable, cost-effective, and non-destructive tool to preliminarily identify problem drywall for corroborative testing such as elemental sulfur content in the suspect drywall.