Development of Methods for Quantification and Apportionment of Metal
Sources, 2000
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Research
Team |
| C. Banic
(MSC, Environment Canada), J. Campbell (U of Guelph), R. Carignan (U
de Montréal), A. Chatt (Dalhousie U), G.C. Edwards (U of Guelph), C.
Grégoire (NRCan, Geological Survey of Canada), M. Lamoureux (St.
Mary's U), P. Rasmussen (Health Canada), W. Schroeder (MSC,
Environment Canada)
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Summary |
Metals in the environment
can arise from both natural and anthropogenic sources. The overall
issue is to determine whether the metals that are posing public health
and environmental problems originate from natural or anthropogenic
sources, and thus identify the most appropriate risk management
strategy. The goal of the Sources research team is to determine what
proportion of observed metal loadings in various ecosystems are due to
atmospheric deposition from anthropogenic activities versus natural
sources by addressing the following research questions:
- What is the magnitude of metal
emissions from natural sources? What are the metal species present
in natural particulate fluxes?
- What are the most appropriate
criteria and methodologies for source apportionment, natural vs.
anthropogenic, of metal releases?
- What is the speciation of metals
deposited from the atmosphere? Is the speciation determined by
source characteristics or by transformations during transport?
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Role in Risk Assessment of Metals in the Environment |
| The
<Sources> research team is determining the partitioning of
observed metal loadings in various ecosystems between atmospheric
deposition from anthropogenic activities versus natural sources.
This is particularly important for ecological risk assessments
(ERA) pertaining to metals in the environment, which require exposure
characterisation.
The <Sources> research will aid in this important step in
ERA through a better understanding of the relative contributions of
natural and anthropogenic sources, through the development of criteria
for source apportionment, and through a more thorough understanding of
transformations of particulates as well as their final transport and
fate in the atmosphere.
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Scientific Background (from 1999 summary) |
| Metals in the environment can arise
from both natural and anthropogenic sources. The overall issue, is to determine whether
the metals that are posing public health and environmental problems originate from natural
or anthropogenic sources, and thus identify the most appropriate risk management strategy.
To address this issue properly, metal releases to the atmosphere must be reliably
quantified both for anthropogenic and natural sources. Additionally, to understand the
role and influence of natural versus anthropogenic metal sources from emission to
deposition, it is important to know the properties of the emissions that influence their
transport and transformation in the atmosphere, such as the distribution of metals as a
function of particle size and the metal species on the particles. There are large uncertainties associated with estimates of natural metal
emissions to the environment (Rasmussen, 1998). Without these natural sources inventories,
the relative contribution of anthropogenic sources cannot be adequately assessed for
regulatory and mitigation purposes. The uncertainties are largely due to technological
limitations and incomplete sources quantification, therefore on of the research program=s
objectives was to develop metal flux measurement methods and to apply them for measuring a
variety of natural sources.
Fine metal particles may be subject to long-range transport.
Therefore, it is imperative, from an ecological risk assessment point of view, to
determine sources of airborne particles and identify individual particles on the basis of
size fraction and their chemical composition, so as to have an improved understanding of
the sources and fates of metals in airborne particulates. The objectives of these studies
are to develop analytical techniques and to assemble criteria which can be used to
determine the source of deposited metals.
Metal emissions from anthropogenic or natural sources may be
transported to the aquatic environment, and can be manifested as enhanced metal
concentrations in lake sediments close to point sources. Such sediment profiles have been
interpreted as evidence for increased anthropogenic metal loading in the recent past
(Lindqvist et al. 1991). In the case of certain elements, however, surface enrichment may
result from natural processes (Carignan and Tessier 1985). The changes that occur after
burial, due to physical, chemicals and biological processes ("diagenesis"), are
important controls on sediment profiles. The sensitivity to sediment diagenesis varies
from metal to metal; therefore the objective was to exploit these characteristics to
determine source emissions.
The objectives of the individual projects are designed to
meet the long-term objectives of the projects which are:
(i) to determine what proportion of observed metal loadings in various ecosystems
is due to atmospheric deposition from anthropogenic activities versus natural sources, and
(ii) to provide high quality emission data, methods, and criteria that can be used
for the ecological risk assessment of metals.
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Practical
Background (from 1999 summary) |
| Over the time frame 1998-2004, we
propose to develop techniques for particulate metal flux measurements and to apply them to
measure natural fluxes from various natural settings (Edwards), to develop new analytical
techniques to determine metal species by particulate size (Lamoureux), and to study the
effect of diagenesis to determine whether remove lake sediment records can be used as
evidence of long-range transport from anthropogenic sources (Carignan). Various funding
options are being explored for the period 1999-2004 (e.g., applications to NSERC for
University-Industry funding in the <Research Network> or <Cooperative Research
and Development> areas). Since it was not expected to begin receiving funding from
these sources until 1999 at the earliest, the 1998-99 research program was implemented on
a budget of $108,000. |
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Overall Goals (from 1999 summary) |
| An overriding goal for the current
funding exercise was to maintain and foster interactions among those MITE researchers who
are involved in research on the sources of metals in the environment. The 1998-99
time-frame was thus seen as a transition year, during which these contacts were maintained
even while we worked on obtaining complementary funding from NSERC and other sources. Each
sub-project was designed to test certain key hypotheses and to yield short-term results
that will help us to refine the experimental approaches for the subsequent field work. |
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References (from 1999 summary) |
| Carignan, R. and A. Tessier, 1985, Science,
228: 1524-1526. Lindqvist, O., K. Johansson,
M. Aastrup, A. Andersson, L. Bringmark, G. Hovsenius, L. Hakanson, A.
Iverfeldt, M. Meili,
and B. Timm. 1991. Water Air Soil Pollut. 55:1-2.
Rasmussen, P.E. 1998. Environ. Geol. 33: 96-108.
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