Elemental baselines and deposition gradients in Sudbury, Canada: views from lichen, moss, snow, and soil

We assessed the spatial extent and source signatures of metal contamination in the Sudbury, Ontario, Canada region using three lichen species (Stereocaulon spp., Cladonia rangiferina, Evernia mesomorpha), moss (Dicranum scoparium), humus forms, mineral soils, and snowpack. Baseline concentrations were established for 23 elements across these seven monitors. Stereocaulon spp. generally shows the highest baseline concentrations for most metals, Cladonia rangiferina the lowest, and Evernia mesomorpha intermediate. In contrast, the moss Dicranum scoparium has a higher concentration of nutrient elements (e.g. Ca, Mg, K) but comparatively low metal concentrations relative to the lichen species. Distances from the city to the baseline concentrations for As, Cd, Co, Cu, Ni, and Pb were compared across media types. Elemental concentrations in snow particulate matter return to baseline within 9–15 km of the city (with one exception at 30 km for Ni), whereas soils remain elevated to 25–46 km. Lichens exhibit a steep ‘principal’ contamination gradient like snow particulate matter but remain elevated until 26–38 km, roughly matching soil patterns and suggesting resuspended legacy contamination. The Bioaccumulation Scale was applied to lichens for cross-species comparison and determining environmentally relevant elements. The scale reduces cross-species variability but does not eliminate species-specific effects. Around the smelters, 13 of 32 elements exceed the environmentally relevant threshold (Bioaccumulation ratio >3.4). This work provides updated baseline values and baseline distances for a region historically impacted by mining activity and integrates multiple media to reveal relationships between modern and legacy contamination.