Nano-scale examinations of the sequestration of metal(loid)s by organic matter and mineral surface coatings in soils
EMSL Project ID
50176
Abstract
Airborne particulate matter (PM) - suspended solid particles with diameters between a few nanometers (nm) and several micrometers - has always been a constituent of the Earth's atmosphere. Man-made PM accounts for only 2-3% of the particle mass emitted globally but the physical and chemical properties of anthropogenic PM, however, are distinct from those of natural PM and have a decisive influence on human health and natural processes. As such mitigation of air pollution hazards requires detailed knowledge of the nature of the particles, their emission sources, transport, and final fate, and their impact on the environment, including human well-being. Organic-rich layers (OL) in the northern and southern hemisphere are the first horizons in undisturbed soils that interact with airborne PM. Studies of smelter-impacted soils show that the concentrations of metal(loid)s decreases exponentially with depth, indicating that metal(loid)s transported by the atmosphere via PM remain predominantly in the upper OL. This project aims to identify sequestration mechanisms of the redox- and/or pH-sensitive metal(loid)s Cu, As, Sb, Pb, Ni and Zn by organic matter (OM) and mineral surface coatings (MSC) in smelter-impacted acidic and near-neutral (reclaimed) soils in Canada. The hypotheses of this project are that the formerly airborne metal(loid)s are sequestered within nano-size phases in OM and MSC and that the identification of these phases will give information about the environmental conditions in nano-scale pore spaces. An important objective of this project is the examination of the chemical environment of a metal(loid) on the surface of OM and MSC as this information could provide fundamental knowledge on the change in the chemical environment (and mobility) of a contaminant across environmental interfaces such as the interface between bulk soil and the interior of OM and MSC. Organic-rich soil samples will be collected from soils that have been impacted by smelter emission of different chemical and mineralogical composition. Organic material and the chemical and mineralogical composition of the collected will be characterized with mass spectroscopy, a C, H, N, S analyser, X-ray diffraction, Infrared spectroscopy and scanning electron microscopy. The chemical environments of the metal(loid)s on the surfaces and the interior of OM and MSC will be examined with X-ray photoelectron spectroscopy (XPS) and a combination of the focused ion beam technology (FIB) under cryo-conditions (for sample preparation), transmission electron microscopy (TEM, for phase analyses and chemical distribution of major elements) and atom probe tomography (APT, for the chemical distribution of trace elements), respectively. The use of XPS, cryo-FIB, TEM and APT is a unique combination of analytical instrument which does not exist to our knowledge in any other facility in North America. The use of this combination will (a) allow the examination of ion- and electron-beam-sensitive OM, (c) provide insides into poorly understood sequestration processes of metal(loid) in organic rich soils and (c) expand our knowledge on nano-scale processes in pore spaces of contaminated soils.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2018-10-01
End Date
2021-03-31
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members