Faculty and Staff

Chemistry
Associate Professor
Phone: 902.420.5652
Office: Science S502
Email: marc.lamoureux@smu.ca

Research Interests:
Chemical speciation of environmental solids; analytical spectroscopy; x-ray absorption fine structure spectroscopy; method development for direct sampling and analysis of solids

Research

Gaseous metal and metalloid pollutants of various chemical forms may absorb onto fly ash and dust particulates. Chemical reaction between these metals/metalloids pollutants and the airborne particulate may induce a change in speciation. These airborne particulates facilitate the redistribution of metal/metalloid pollutants via the atmospheric environment [1]. Knowledge about the chemical speciation in airborne solids of metal and metalloids pollutants is urgently needed in order to develop appropriate environmental protection regulations and better air quality monitoring strategies for health protection. Airborne metal/metalloids pollutants can find their way into the human body through inhalation of air particulates. Since small air particulates (>10 µm) are likely to be retained by the lungs, the associated metal/metalloid pollutants can be transported to vital organs some distance from the lungs. This can be detrimental to these organs [2] because some pollutants are extremely toxic even at low concentration (e.g. As and Se) and can accumulate in these organs (e.g., Pb) [3].

The research program focuses on in situ solid state chemical speciation of some metals (e.g. Pb) pollutants associated with air particulates. It is presently supported by Natural Sciences and Engineering Research Council (NSERC) and the synchrotron x-ray beam time is provided (in-kind contribution) by Stanford Synchrotron Research Laboratory (SSRL) which is supported by the US Department of Energy, Office of Basic Sciences.

Air particulate are collected by multi-stage air filtration through series of specially designed thin sheet filters of decreasing porosity or by high volume cascade impactors. This provides size fractionation of these particulates. The air particulates collected on filters are investigated by x-ray absorption fine structure (XAFS) spectroscopy to determine the in situ true chemical speciation of metal pollutants associated with air particulates of various sizes. The total concentration of metal-containing species bound to air particulates is determined by graphite furnace atomic absorption spectrometry (GFAAS). XAFS is a powerful technique for determining qualitatively [4] and quantitatively [5-6] the chemical speciation of unknown materials. Both near edge x-ray absorption fine structure (NEXAFS) spectrometry, which allows the determination of the oxidation state of an element [6], and the extended x-ray absorption fine structure (EXAFS) spectrometry, which allows the determination of the local chemical environment (i.e., the chemical speciation of an element [5], are used in this investigation.

The significance of this research is its impact on the development of appropriate environmental protection regulations, of air quality monitoring for health protection, and of waste remediation strategies. In addition, this research will provide better understanding of the physical and chemical characteristics of metal and metalloid pollutants in the atmospheric environmental. Finally, this research will provide crucial, new information for the development of better models to assess and predict the transport and fate of metal and metalloids pollutants in the atmospheric environment.

Other areas of research carried on by the students under Dr. M. Lamoureux supervision are as follows:

• Development of improved method to analyze solid samples.
• Development of novel pre-concentration techniques onto various solid sorbents for solid sampling using atomic absorption spectrometry.
• Solid state chemical speciation of contaminated soils and sediments.
• Construction of new and improved collectors for the sampling of airborne particulate matter.

Research done to propose a better technique for the analysis of solid samples, such as human fingernails was carried out. The aim was to develop a method to determine cadmium and lead in human fingernails using solid sampling techniques with graphite furnace atomic absorption spectrometry. The composition of solid samples like fingernails can indicate significant details such as possible intoxication of heavy metals. Solid sample digestion is one of the currently used methods but is plague by contamination problems from reagents and reduction in the sensitivity due to dilution effect. We are reporting the possibility of determining the concentration of cadmium and lead directly in the solid state using ultra sonic slurry sampling coupled with graphite furnace atomic absorption spectrometry (USS-GFAAS). Comparison between sample digestion and ultrasonic slurry sampling indicates that lead and cadmium can be determined at a very low concentration (i.e. pg/mg) by Applied Spectroscopy USS-GFAAS. Results and further details will be published. The above research was also presented in the form of a poster (no. 16), in the 44th International Conference on Analytical Sciences and Spectroscopy, August 9-12, 1998 [7].

Research on the determination of some trace metals in natural water using complexation followed by sorption onto activated charcoal as a pre-concentration step for slurry sampling graphite furnace atomic absorption spectrometry is also in progress. The interference of chemicals such as chloride ions (ubiquitous in water) poses a problem in the determination of trace metals in natural water samples by GFAAS. The pre-concentration step allows for the trace metals of interest (e.g., Cu or Mn) to be complexed by 8-hydroxyquiniline followed by adsorption onto pre-cleaned activated charcoal. Using this technique many problems of analysis were removed prior to its determination using ultra sonic slurry sampling graphite furnace atomic absorption spectrometry. The advantages associated with this technique are (1) the separation of trace metals from the interfering matrix and (2) the increase in the effective concentration of trace metals. The above mentioned work was also presented (poster no.15) on the 44th International Conference of Analytical Sciences and Spectroscopy, August 9-12, 1998 [7].

The chemical speciation of metals in airborne particulate matter is also investigated using the synchrotron x-ray spectroscopy. The characterization of particulate matter by extended x-ray absorption fine structure (EXAFS) spectrometry. Indirect methods is commonly used for solids but often result in contamination, dilution or unpredictable changes in the speciation. Direct methods such as Rutherford Backscattering Spectroscopy (RBS) and solid state NMR also exist, nevertheless they are also plagued by selectivity, sensitivity and incompatibility. EXAFS on the other hand is a noninvasive, nondestructive, quantitative technique that allows analysis of samples in situ. Significant information such as the identity of the entities surrounding the excited atom, their distance from the excited atom as well as the number the backscatterers can be obtained. Indoor air samples under controlled and uncontrolled conditions were collected onto mixed cellulose ester membrane filters by air filtration. Surface dust was also sampled by sweeping surfaces (e.g. bench tops and shelves) with a brush into a plastic bag. These samples were analyzed for lead, copper and zinc. Analysis of the dust sample from EXAFS for Cu near neighbour pairs indicates the presence copper hydroxychloride (Cu(OH)Cl) and for Zn near neighbour pairs indicates possible presence of a phosphate-containing Zn compound of the form Zn2Fe(PO4)2. The above described research was also presented on the 44th International Conference of Analytical Sciences and Spectroscopy as a poster no. 17, August 9-12, 1998 [7].

Development of new collectors for sampling air particulate matter is also an important area of research. We have developed an air particulate collector that allows the separation of particulates in two fraction sizes. Portable, low concentration detection of lead for one hour sampling has been proved successful. The problems associated with other techniques such as dilution, interference of other metals and high blank value have been eliminated by using this technique.

Literature Cited

• J.O'M. Bockris, Environmental Chemistry, Plenum Press, New York, 1977.
• S.E. Manahan, Environmental Chemistry, Willard Grant Press, Boston, 1979.
• M.B. Jacobs, The Analytical Toxicology of Industrial Inorganic Poisons, Interscience Publishers.
• X-ray Absorption: Principles, Application, Techniques of EXAFS, SEXAFS, and XANES, D.C. Koningsberger and R.Prins, Eds., New York, 1998.
• M.M. Lamoureux, J.C. Hutton, D.L. Styris, and R.L. Gordon, Appl. Spectrosc. 49, 808-812, (1995).
• S. Bajt, S.B. Clark, S.R. Sutton, M.L. Rivers, and J.V. Smith, Anal. Chem. 65, 1800 (1993).
• 44th International Conference on Analytical Sciences and Spectroscopy program and abstract, poster no. 15, 16, 17., Pg. AB-56-57, August 9-12, 1998.