| Dropping of senescent foliage (litterfall) represents the largest flux of mercury to boreal forest soils, and understanding the source(s) of this Hg (new atmospheric vs. recycled inputs) is crucial for a complete and accurate Hg mass-balance budgets. Stomatal uptake of atmospheric gaseous elemental Hg (Hg(0)), root uptake of soil Hg, and retention of ionic Hg (Hg(II)) from wet deposition were evaluated as Hg input pathways for boreal forest canopies at the Experimental Lakes Area (ELA, northwestern Ontario). Mechanistic experiments were conducted using a new dynamic chamber for measuring Hg(0) exchange from foliage, and stable Hg isotope tracers. Results were consistent with the general concensus that most of the Hg in litterfall is derived from stomatal uptake of Hg(0), and not from root uptake of soil Hg. Some of the Hg in litterfall may be derived from long term retention of Hg(II) from wet deposition. |
