Concentration and Distribution of Metal Elements at the Surface of Balsam Fir Foliage by Micro-Proton Induced X-ray Emission

Abstract

Metal contaminations at the surface of balsam fir (Abies balsamea (L.) Mill.) needles collected at two locations in southern Quebec were determined by micro-PIXE (micro-proton induced X-ray emission) with scanning depth of 3−4 or 45−50 μm and scanning spacing from 15 to 250 μm. At adaxial surfaces, concentrations of Al, Si, Ca, Ti, Fe, and Zn were significantly (P < 0.05) higher at the near-urban site than at the mountainous location. Accumulation of Mg, Al, Si, K, Mn, Fe, and Zn was significantly (P < 0.01) higher at surfaces of unwashed needles as compared to chloroform-washed needles, which shows significant metal accumulation in/on epicuticular wax layers. Metal deposits, except Mn, in epicuticular wax layers were significantly affected by washing with acidic solution. Distributions of Mg, K, Mn, and Zn deposits at the surface were lower around central regions than near foliar edges, while Si was higher around the central area. Scanning to the 45−50 μm depth showed significant accumulation of Ni on either side of the foliar center groove.

Plants and Atmospheric Aerosols

“…Studies with two-stage extraction of leaf surfaces with water followed by chloroform (Mo et al 2015;Popek et al 2013;Saebo et al 2012;Sgrigna et al 2015), and analysis of magnetic properties of leaves in high-aerosol urban environments (Hofman et al 2014), have shown that fine aerosols, including those with magnetic properties, become embedded in the surface waxes. This confirms earlier results with other techniques (Kozlov et al 2000;Lin and Schuepp 1996;Oliva and Raitio 2003;Oliva and Valdes 2004;Simmleit et al 1989).…”

“…The thickness of the LBL is in the range of micrometers to millimeters, increasing with leaf size and decreasing with wind speed. The boundary layer is thinnest at leading edges (Grace and Wilson 1976), increasing deposition near leaf margins Lin and Schuepp 1996;Wang et al 2015;Wild et al 2006). Within the viscous (quasi-laminar, turbulence-free) sublayer of the LBL, transport of gases and ultrafine aerosols by Brownian motion leads to rapid diffusion to the leaf surface.…”

“…Quantification of total leaf loading of aerosol-borne compounds may be achieved by proton-induced X-ray emission (PIXE) (Lin and Schuepp 1996;Simmleit et al 1989) or by inductively coupled plasma (ICP), either of material on the leaf surface or of material washed from the surface (Bertolotti et al 2014;Kalinovic et al 2016;Mori et al 2015a;Quayle et al 2010;Santos et al 2015;Schleppi et al 2000). Measurement of magnetic susceptibility or saturation isothermal remanent magnetization (SIRM) is a relatively new method to determine foliar-deposited aerosols in urban vegetation (Hofman et al 2014;Kardel et al 2011;Matzka and Maher 1999;Sant'Ovaia et al 2012;Urbat et al 2004).…”

Manganese as a site factor for epiphytic lichens

“…Translocation of Mn to the bark is apparently a widespread mechanism in trees to avoid toxic concentrations of free Mn As a consequence of their high mobility, Mn 2+ ions are also readily (re-)absorbed by tree canopies. Most of the absorbed Mn remains on the canopy surface, i.e., in the foliage (especially in epicuticular wax layers) or in the bark (LIN et al 1995, LIN & SCHUEPP 1996. Mn absorbed in the canopy is partly derived from precipitation and partly from aerosols (SCHMIDT 1987), whereas some ions are re-absorbed after leaching.…”

“…The main source of Mn in forest ecosystems is the soil, from which Mn is taken up by the tree roots and then translocated to all living tissues including the foliage and stem tissues that are designated to become bark soon (LÖVESTAM et al 1990, LIN et al 1996, HAUCK et al 2002a. HAUCK et al 2001b, 2002a, SCHMULL & HAUCK 2003a, HAUCK 2005.…”