Large-scale bryomonitoring of atmospheric trace elements in eastern Canada: Spatial patterns, ecological risk, and...

Atmospheric deposition of trace elements is a key pathway of diffuse environmental contamination, influencing ecosystems over broad spatial scales, yet it remains poorly characterized in many low-population regions. This study represents the first large-scale, high-resolution bryomonitoring survey conducted in North America to assess the atmospheric deposition of trace elements in New Brunswick, Canada. Following ICP-Vegetation guidelines, Pleurozium schreberi moss samples were collected at 205 sites spanning a wide range of ecosystems, together with site-level data describing climate, vegetation, land use, and substrate conditions, and analyzed for 22 elements using inductively coupled plasma mass spectrometry (ICP-MS). Spatial distributions of elements were mapped using ordinary kriging and integrated into an ecological risk index, indicating an overall low risk at the provincial scale. Nevertheless, the identification of a pronounced north-south gradient for several toxic trace elements (As, Cd, Hg, Ni, Pb, Zn), along with evidence of Cd-Hg-Pb-Zn co-occurrence highlights priority areas and element assemblages for future investigations into emission sources and transport pathways. Multivariate analyses showed that environmental variables (e.g., precipitation, pH, road distance) explained a modest but statistically significant proportion (6.1%) of concentration variability, while univariate analyses clarified element-specific responses. Marked spatial heterogeneity at both local and regional scales emphasizes the importance of establishing local baseline values to support long-term monitoring and detection of temporal change. Overall, this work provides a methodological and conceptual foundation for future bryomonitoring initiatives in North America, supporting improved assessment of spatiotemporal trends in atmospheric contaminants and contributing to large-scale evaluations of cumulative deposition and ecological risk.