| Project Title |  |
| Project
A2: in situ solid state chemical speciation of some metal pollutants
associated with ground level particulate matter.
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| Research Team | |
| Dr. M.
Lamoureux, St. Mary’s Univiversity. Email: marc.lamoureux@stmarys.ca Tel: 902-420-5652
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| Project Summary | |
| The main objective of this work was
to determine the concentration and the chemical speciation of Ni, Cu and Pb as a function
of atmospheric particulate size. We evaluated different membrane filters with regard to
sampling efficiency with a high volume cascade impactor, ease of sample preparation of the
membrane filters for ultrasonic slurry sampling with graphite furnace atomic absorption
spectrometry (GFAAS) or inductively coupled plasma mass spectrometry (ICP-MS), and matrix
interferences with the analyte of interest (Cu, Ni, and Pb) due to the chemical nature of
the membrane filter. It was found that mixed cellulose ester (MCE) membrane filters are
more suitable for GFAAS analysis whereas MCE or glass fibre membrane filters worked
equally well with ICP-MS. The cascade impactor allowed the collection of atmospheric
particulate matter separated by size, in five different fractions. Therefore, methods have
been developed to determine Ni, Cu and Pb directly in the particulate matter (without acid
digestion) as a function of particle size. Preliminary results for Pb, Cu, and Ni
determined from indoor or outdoor particulate samples show that the metal concentration is
inversely related to the particulate diameter for all metals investigated. We also
characterized the particular matter (as a function of particle size) by scanning electron
microscopy (SEM). Because MCE filters were not appropriate for SEM imaging, particulate
matter was also collected on glass fibre filters. We developed a procedure that allows the
simultaneous collection of particulate matter on both glass fibre and MCE filters using a
single cascade impactor. This allowed the same particular matter to be imaged by SEM
(i.e., particulates collected on glass fibre) and analysed for total concentration of each
analyte metal with GFAAS (i.e., particulate collected on MCE). The SEM images show clearly
that particular matter of larger diameters (>1.5 micron) are composed of salt-like
particulates (particles with sharp edges) and possibly of carbonaceous material (smooth
spherical particles). Characterization of Pb, Cu, and Ni species associated with
atmospheric particulate matter was carried out with synchrotron x-ray absorption fine
structure (XAFS) spectroscopy. Preliminary results show clearly that Cu from indoor
particulate matter is distributed predominantly as copper metal (dust) and copper oxide.
This is the first report on the chemical nature of a metal species as a function of
atmospheric particulate size using XAFs.
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