Bardelli Fabrizio, Rimondi Valentina, Lattanzi Pierfranco, Rovezzi Mauro, Isaure Marie-Pierre, Giaccherini Andrea, Costagliola Pilario
Università di Roma La Sapienza, Roma, Italy.
CNR-Nanotec, Italy.
Environ Sci Process Impacts. 2022 Oct 19;24(10):1748-1757. doi: 10.1039/d2em00239f.
Tree bark near former mercury (Hg) mines and roasting plants is known to have exceptionally high (up to several mg kg) Hg concentrations. This study explores the change of Hg speciation with depth (down to 25-30 mm from the outermost surface) in black pine () bark by means of high-resolution X-ray absorption near edge structure (HR-XANES) spectroscopy at the Hg L-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, 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.
已知在以前的汞（Hg）矿和焙烧厂附近的树皮中汞浓度异常高（高达数毫克/千克）。本研究通过汞L边的高分辨率X射线吸收近边结构（HR-XANES）光谱，探究黑松树皮中汞形态随深度（从最外表面向下至25 - 30毫米）的变化。对HR-XANES光谱进行主成分分析和线性组合拟合表明，在最外层（距表面约0 - 2毫米），大约50%的汞以纳米级的黑辰砂（nano-β-HgS）形式存在。在更深的树皮层中发现汞有机物种（与硫醇基团结合的汞）逐渐增加，而在最深层中纳米级黑辰砂可能降至检测限以下。值得注意的是，树皮层中不含辰砂（α-HgS），在附近土壤中发现了辰砂以及β-HgS（块状），并且树皮层中也不含汞，汞是采样树木周围大气中的主要汞物种。这些观察结果表明，纳米级黑辰砂至少部分并非源自周围土壤中机械捕获的风吹颗粒物，而是气态单质汞与树皮组织之间生化反应的产物。
