Correspondence/Rebuttal pubs.acs.org/est
Response to Comment on “Sphagnum Mosses from 21 Ombrotrophic Bogs in the Athabasca Bituminous Sands Region Show No Significant Atmospheric Contamination of ‘Heavy Metals’”
L
samples, comparable Pb concentrations have been reported for specimens from southernmost South America and Antarctica.4,5 However the moss data from the ABS region is viewed, the Pb concentrations are low. Thorium concentrations, taken to reflect the abundance of mineral dust particles in the moss, are plotted in the same way (Figure 1b). Again, as a point of reference, peat samples from the EGR bog and dating from the mid-Holocene, contain 0.07 ± 0.02 mg/kg Th; n = 18.6 All of the moss samples from the ABS region are within a factor of 8 of the “background” value for Th in ombrotrophic peat. It is clear from these illustrations that Pb (Figure 1a) and Th (Figure 1b) exhibit similar spatial distributions, with greater concentrations closest to the midpoint between the two upgraders. A plot of Pb/Th against distance (Figure 1c) shows the ratio ranges from 2.2 to 3.9 in every sample
