Tree‐Ring Analysis for Tracing the History of Pollution: Application to a Study in Northern Sweden

This study attempted to assess the validity of tree‐ring analysis in tracing the history of pollution in an area exposed to high atmospheric concentrations of heavy metals from a smelting complex. Tree cores, bark samples, and soil samples were collected from two sites, one close to and the other distant from the source of atmospheric emission. The samples were analyzed for cadmium, zinc, copper, and lead. It could be shown that the reduction of growth at the site of high exposure was positively correlated with the concentrations in the tree cores of copper and lead but not zinc and cadmium. The data show clear evidence for lateral transport of zinc and cadmium but not for copper and lead. Since the reduction of growth did not correlate positively with sulfur emissions into the atmosphere, it is concluded that the effect of the heavy metals was dominant and that the reduction was causally related to the heavy metal emissions.