Contrasting Effects of Road Dust and Atmospheric Dust on Carbon Accumulation in Eastern Canadian Ombrotrophic Peatlands

Abstract Limited research has been conducted on the role of atmospheric dust as a nutrient source for peatlands, and none has studied the effects of localized and intense road dust on peatland carbon (C) accumulation. To compare the effects of dust deposition from these two sources on peatlands, we examined three ombrotrophic peatlands adjacent to unpaved (gravel) roads in eastern Canada. We find that road dust deposition increases the ash content of peat and decreases its stoichiometric ratios of C, nitrogen (N), and phosphorus (P), with the greatest changes occurring at the site receiving the highest road dust deposition. The dust record since 5,500 cal BP, reconstructed using ICP‐MS analysis of lithogenic elements in a peat core, reveals seven dust episodes. The most recent episode, predominantly from road dust, exhibits a flux 19–95 times higher than the background atmospheric dust flux depending on the reference element. In the catotelm layer of the peat core, the atmospheric dust flux exhibits significant positive correlations with C, N, P, and potassium (K) accumulation rates alongside negative correlations with the C:N and C:P ratios. In contrast, the C accumulation rate is lowest closest to the road and increases with distance away from the road as a result of changes in vegetation composition, nutrient availability, and water levels. The different effects of atmospheric dust and road dust suggest that there may be a threshold effect of dust or nutrient inputs, especially P, on peatland C accumulation.