Airborne metal pollutants in high elevation forests of southern Quebec, Canada, and their likely source regions

Atmospheric metal pollution in high elevation forests of southern Quebec was investigated through analysis of airborne particulates, calculation of elemental enrichment factors, and air mass back-trajectory analysis. Metal concentrations (ng m −3) of Al, As, Cu, Fe, La, Mg, Mn, Na, Sb, V, and Zn in airborne particulates varied significantly throughout 1993. The Mn concentration at Roundtop Mountain in southern Quebec was generally higher than the reported concentration from the Champlain Valley in the northeastern USA. Concentrations of Mn and those of Al, La, V, and Zn were significantly ( P ≤ 0.05) correlated. Except for the probably local soil-dust origin of Fe and La, enrichment factors suggested that the metal composition of airborne particulates could be attributed to their long-range transport through the atmosphere. The wind direction frequency measured at the research site in a mountain forest was not suitable for identification of likely source regions for metal pollutants. However, air mass back-trajectories indicated that air parcels that moved over Canadian and US industrialized and metropolitan areas may contribute to Mn pollution in rural high elevation regions. This study supports the contention that the atmospheric input of toxic trace metals should be a matter of concern in high elevation forests.