The quantitative analysis of sugar maple tree rings by laser ablation in conjunction with ICP-MS

This study reports on the quantitative analysis of sugar maple (Acer saccharum Marsh.) tree rings by laser-ablation ICP-MS (LAS). Differences in ablation were corrected using C-13 as an internal standard. Spatial variation in element distribution within individual tree rings was low, allowing individual tree rings to be used as calibration standards. The relative standard deviation (RSD) for element concentrations within tree rings were 15% for Mg, 15% for Ca, 9% for K, and 16% for Pb. This variation is likely doe to element distribution and not the ablation process; the RSD for C-13 was <4%. Tree cores were taken from three sugar maple trees adjacent to a major highway, 24 km east of Toronto. Concentrations of Ca, Mg, and K generally declined from pith to cambium, a Feature commonly observed in tree boles. Peaks in Pb concentration, between 3 and 5 mg Pb kg(-1),were found in tree rings formed between 1940 and 1970, although there was considerable year-to-year variation within each tree, and the timing and magnitude of the Pb peaks differed between trees. Lead concentrations decreased in wood formed after 1970 so that by the 1980s, Pb concentrations were around 1 mg kg(-1), reflecting changes in Pb deposition into the woodland.