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Surface Chemistry & Environmental Quality
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Platinum Nanoparticulates in Diesel Fuel Emissions
The platinum (Pt) nanoparticle project is a new collaboration between
the University of Minnesota - Twin Cities (Brandy Toner) and the
University of Wisconsin - Madison (Martin Shafer and James Schauer) to examine Pt speciation in aerosols emitted from diesel burning engines. Platinum is added to diesel fuel as a soluble
organic compound along with another organo-metallic, such as Ce, to improve combustion. In the engine, the Pt compounds are reduced and form nano- to micrometer
scale, Pt-coated, Ce-carrier particles that exit the vehicle through the tailpipe. Platinum-amended fuels
(Pt-FBC) are currently approved in Europe for broad use, and in the US for many
specialty diesel vehicles. Martin Schafer and co-workers recently completed a study of Pt and Ce emissions from diesel engines
burning a Pt-FBC (Shafer et al., 2006). Schafer et al.
determined that in the "engine-out" emissions of water-soluble Pt represented nearly 3 % of total emissions and a
large fraction of the water soluble Pt (44 ± 8%) was present as nanometer-sized
particles. The current toxicology
paradigm is that for environmental Pt to exhibit significant human toxicity it
must be in specific water soluble forms. In
occupational exposure settings Pt-compounds can be powerful allergens and several studies suggest that the increase in
the incidence of asthma may, in part, be related to environmental Pt exposure. Although chemical speciation dictates the toxicity and reactivity of these
Pt-coated nano-particulate materials, to date, there is little definitive information on
Pt speciation in environmental particles since operational definitions and measurements for Pt toxicity have been the standard.
Through our collaboration, we will be conducting
spatially-resolved Pt
X-ray absorption spectroscopic (micro-XAS) measurements on Pt-FBC
emissions to: (1) determine Pt speciation within particulate
Pt-FBC
emissions, (2) track speciation changes due to reactions occurring in
the
environment, and (3) assess the toxicity of Pt-FBC particulate
emissions.
Shafer,
M.M., J.J. Schauer, W. Copan, J. Peter-Hoblyn, B. Sprague, and J. Valentine (2006).
Investigation of platinum and cerium from use of a fuel-based catalyst. SAE Journal – 2006-01-1517.
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Arsenic Sequestration by Industrial By-Products
The arsenic
sequestration project is a new collaboration between
the University of Minnesota - Twin Cities (Brandy Toner) and University
of Wisconsin - Madison (Craig Benson, Seung-Hak Lee, and Stacy Metz) to
examine the mechanism(s) of arsenic (As) removal from water by an
industrial by-product, iron foundry slag. Arsenic contamination
of drinking water, from natural and anthropogenic sources, is a common
environmental phenomenon that raises great concerns about human health.
The U.S. Environmental Protection Agency has assigned a 10
microgram per liter Maximum Contaminant Level for arsenic in drinking
water. Therefore, development of cost-effective technologies to
achieve this low concentration of As in water are in great demand (for
a review, see Choong et al., 2007). Stacy Metz and co-workers
have examined the removal of arsenate and arsenite from water by iron
foundry slag materials produced in Wisconsin. Iron foundary slags
contain oxides of Si, Al, Ca, Mg, and Fe, as well as pure Fe (Metz,
2007), and represent an opportunity to use an industrial waste product
for water remediation. Through our collaboration, we have begun
conducting synchrotron-radiation X-ray absorption spectroscopic studies
of the Fe and As speciation within reacted iron foundry slag materials
to determine the mechanism(s) of As sequestration by these materials.
Choong, T.S.Y, Chuah, T.G., Robiah, Y., Koay, G.F.L, and Azni, I.
(2007) Arsenic toxicity, health hazards and removal techniques from
water: an overview. Desalination 217:139-166.
Metz, S.E. (2007) Iron foundry slags as reactive materials for arsenic
removal from groundwater. M.S.Thesis in Geological Engineering.
University of Wisconsin - Madison.
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Atrazine Degradation by Manganese Oxide Minerals
*Under Construction*
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Treated Wastewater & Biosolids in Soils: Phosphorus Speciation, Transport, and Accumulation
The phosphorus (P) speciation project is a new collaboration in the Department of Soil, Water, and Climate between Paul Bloom and Brandy Toner. Paul Bloom has secured funding through an international collaboratory program, BARD
- Binational Agricultural Research and Development Fund, to
examine P speciation in wastewater (TWW) and biosolid (BS) treated
soil.
*There is currently funding for a postdoctoral researcher on this project.*
It is well-documented that P accumulates in soils after prolonged
irrigation with TWW or application of biosolids, however, there is
limited knowledge of P chemical forms in TWW and BS treated soils. The
different P forms can have a wide range of availability to plants and
mobility in surface runoff and down a soil profile, into shallow
groundwater and drainage. In the proposed research, we shall study the
fate of sewage-originated P (sewage-P, including TWW-P and BS-P) in
soils of Israel and Minnesota in micro (particle surface), meso
(microcosms, lysimeters), and whole field and profile depth scales,
focusing of the processes of retention, transformations, transport,
accumulation, and leaching. The study will make use of existing fields
in both countries with long known history of TWW or BS application. We
shall combine common methods of P extractions and fractionation with
advanced tools of SEM-EDXS, synchrotron X-ray micro X-ray
fluorescence (XRF) and micro X-ray absorption near edge structure
(XANES) spectroscopy to identify modes and
processes of P retention and accumulation. The knowledge gained in this
study will lead to maximizing the beneficial use of TWW and BS and
minimize adverse effects on the environment through P loss to surface
and ground waters. It is also believed that the procedures developed in
this project will have the potential to be used for other important P
systems (e.g., application of manures or various effluents) after
proper modification.
References:
Hettiarachchi, G.M., K.G. Scheckel, J.A. Ryan, S.R. Sutton, and M.
Newville. 2006. µ-XANES and µ-XRF investigations of metal
binding mechanisms in biosolids. J. Environ. Qual. 35: 342-35.
Pierzynski, G. M. Logan, T. J. Traina, S. J. Bigham, J. M. Phosphorus
chemistry and mineralogy in excessively fertilized soils: quantitative
analysis of phosphorus-rich particles. Soil Science Society of America
Journal. 1990. 54: 6, 1576-1583.
Sato, S., D. Solomon, C. Hyland, Q. Ketterings, and J. Lehmann. 2005.
Phosphorus speciation in manure and manure-amended soils using XANES
spectroscopy. Environ. Sci. Technol. 39:7485-749
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