Biomonitoring of atmospheric depositions of rare earth elements and other elements in Quebec, Canada

Abstract

Despite the growing demand for rare earth elements (REE) in technological applications and the potential risks associated with their environmental release, few studies have focused on atmospheric levels of REE. Nowadays, in Canada, only one active mine is exploiting REE ores. In Quebec (eastern Canada), several exploration projects are underway; however, no mine is currently active, and few human activities are likely to represent a source of atmospheric REE. Thus, we established the first estimates of atmospheric depositions of REE and other elements (e.g., transition metals) in Quebec and identified the current emission sources by comparing these depositions across different land uses (forest, rural, and anthropogenic). We also report on some elements of interest for moss physiology and biogeochemistry (e.g., K, Na, Mg, and Ca). We employed a biomonitoring approach, utilizing Pleurozium schreberi as an indicator of elemental composition in atmospheric deposition. 210 sites were sampled across southern Quebec, in the most densely populated areas of Quebec. Elements were analyzed by ICP-MS and ICP-OES. Atmospheric depositions of REE (and other elements) are low in Quebec compared to other biomonitoring studies worldwide, with ∑REE average values of 2.63 ppm in the mosses. Hotspots were detected in urban, tourist, or industrial areas, with concentrations reaching up to ∑REE = 32.14 ppm. Overall, the origin was mainly terrigenous, as shown by the enrichment factor (EF ≈ 1 for all REE). However, a few elements (Cd, Zn, Ag, B, Mn, Sb, K, Ca, and Cu) exhibited EF > 10, indicating contamination at nearly all locations.