Radioactivity in smoke particulates from prescribed burns at the Savannah River Site and at selected southeastern United States forests

In this study we compare airborne radionuclide concentrations during prescribed burns at the Savannah River Site (SRS) and a sample of forests in the Southeastern United States. The spatial trends of airborne radionuclide concentrations from prescribed burn areas at SRS are also characterized. Total suspended particulate (TSP) samples were taken at three settings (subsequently termed burn sample populations): during prescribed burns at SRS (n = 34), on nonburn days at SRS (n = 12) and during prescribed burns at five offsite locations in the Southeastern United States (n = 2 per location). Mass concentrations of TSP were calculated and alpha, beta and gamma spectroscopy was performed to determine radionuclide activity concentrations. Spatial correlation in radionuclide concentration was assessed and ordinary kriging was used to create continuous surface maps across our study area. Median activity concentrations of natural radionuclides including 40K, thorium and uranium isotopes (n = 34) were higher in samples from SRS prescribed fires (p < 0.02) compared to offsite locations (n = 10) and nonburn days (n = 12). Median gross beta activity was also higher at SRS (p < 0.0001). Median concentrations of anthropogenic radionuclides did not significantly differ among burn sample populations except for 238Pu (p = 0.0022) and 239, 240Pu (p = 0.014) with median concentrations of 8.41 × 10−4 and 6.72 × 10−5 pCi m−3 at SRS compared to 1.55 × 10−4 and −7.07 × 10−6 pCi m−3 (nonburn days) and 1.46 × 10−4 and 2.78 × 10−6 pCi m−3 (offsite burns) respectively. Results from our spatial analysis found that only 40K demonstrated significant spatial correlation (X2 = 15.48, p = 0.0004) and spatial trends do not appear to directly link areas with higher activity concentrations with SRS facilities.