Trace elements in Sphagnum moss waters as indicators of the chemical reactivity of contemporary atmospheric dusts: comparison with peat bog porewaters

Abstract

Open-pit mining and other industrial activities generate dusts containing trace elements (TEs) that can be released into aquatic and terrestrial ecosystems. The release of these TEs can be either beneficial or harmful, depending on their concentration, chemical speciation, and toxicity. Sphagnum mosses from ombrogenic peatlands have been used for decades to monitor atmospheric deposition of TEs, but there have been few studies of the water they contain. Sphagnum fluids and peat porewaters are acidic (pH ≤ 4), making both suitable for dust dissolution. Previous studies used near-surface peat porewaters to assess TE bioaccessibility due to open-pit bitumen mining in the past. Here, TEs were determined in waters extracted from living Sphagnum mosses collected in bogs from the same mining and remote locations in Alberta, Canada. Trace elements increased in concentration toward industry, reflecting the increased rates of dust deposition from mining. Concentrations were greater in moss waters compared to peat porewaters, likely due to the increase in rates of dust deposition over time. For example, Y, Fe, and Th were enriched >100×; V and Ni, up to 40×; and As, Cd, Pb, Sb, and Tl, up to 20×, in moss waters near mining activities, relative to the reference sites: none of these elements were enriched >10× in peat porewaters. Sphagnum moss water is a promising and sustainable new tool for estimating TE bioaccessibility in contemporary atmospheric dusts of natural and anthropogenic origin.