Pinus nigra bark from a mercury mining district studied with high resolution XANES spectroscopy. Issue 10 (16th August 2022)

• Record Type: Journal Article
• Authors: Bardelli, Fabrizio; Rimondi, Valentina; Lattanzi, Pierfranco; Rovezzi, Mauro; Isaure, Marie-Pierre; Giaccherini, Andrea; Costagliola, Pilario
• Is Part Of: Environmental science. Volume 24:Issue 10(2022)
• Page Start: 1748
• Page End: 1757
• Publication Date: 2022-08-16
• Subjects: Environmental monitoring -- Periodicals; Biological monitoring -- Periodicals; Environmental chemistry -- Periodicals; 363.7363
• DOI: 10.1039/d2em00239f
• Languages: English
• ISSNs: 2050-7887

Abstract

Abstract : HR-XANES data suggest that atmospheric (gaseous) elemental mercury (Hg(0)g ) is transformed to inorganic Hg(ii )-sulphides at the bark surface and subsurface, and further transformed to organic Hg-dithiolate phases at increasing depth inside the bark. Abstract : Tree bark near former mercury (Hg) mines and roasting plants is known to have exceptionally high (up to several mg kg −1 ) Hg concentrations. This study explores the change of Hg speciation with depth (down to 25–30 mm from the outermost surface) in black pine ( Pinus nigra ) bark by means of high-resolution X-ray absorption near edge structure (HR-XANES) spectroscopy at the Hg LIII -edge. Principal component analysis and linear combination fitting applied to the HR-XANES spectra suggested that in the outermost layer (∼0–2 mm from the surface), roughly 50% of Hg is in the form of nanoparticulate metacinnabar (nano-β-HgS). A progressive increase in Hg-organic species (Hg bound to thiol groups) is found in deeper bark layers, while nano-β-HgS may decrease below the detection limit in the deepest layers. Notably, bark layers did not contain cinnabar (α-HgS), which was found in the nearby soils along with β-HgS (bulk), nor Hg 0, which is the main Hg species in the atmosphere surrounding the sampled trees. These observations suggested that nano-β-HgS, at least in part, does not originate from mechanically trapped wind-blown particulates from the surrounding soil, but may be the product of biochemical reactions between gaseous elemental Hg and the bark tissue.