Tree rings as bioindicators of lead and cadmium pollution: the case of Rouyn-Noranda's urban trees

The project focuses on the analysis of heavy metals in tree rings, in particular lead and cadmium, resulting from pollution from the Horne smelter. The study is limited to a 5 km radius around the smelter, located in Rouyn-Noranda, Quebec. Despite emission restriction protocols, the absence of ecological monitoring makes it difficult to assess the effect of these measures on metal bioaccumulation in trees. This study assesses whether tree rings in Rouyn-Noranda's urban trees can indicate exposure to lead and cadmium, shedding light on the impact of pollution on trees and residents. In a call to the public, a set of 50 trees - spruce, pine, larch and cedar - were selected from public and private spaces to accurately reflect the immediate environment influenced by the smelter. For each tree, a 2 cm diameter wood core was extracted at a height of 1.30 m. The portion of the samples corresponding to the 2018-2022 period was analyzed at the Delta-Lab in Quebec City. Preliminary results indicate that within this restricted 5 km circle there is no significant decrease in metal concentration with distance from the smelter. Differences in bioaccumulation between tree species were observed for cadmium and lead, where cedar seems to accumulate more than other species.