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| Titel |
Reconstructing the environmental impact of smelters using Pb isotope analyses of peat cores from bogs: Flin Flon, Manitoba and Harjavalta, Finland |
| VerfasserIn |
W. Shotyk |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250071615
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| Zusammenfassung |
| Located on the Manitoba – Saskatchewan border, the city of Flin Flon has been home to a
metallurgical complex since 1930, processing Cu and Zn ores from surrounding mines and
consisting of a concentrator, Zn plant, and Cu smelter. Peat cores were collected from two
sites, dated using 210Pb, and measured for a broad suite of potentially toxic trace metals. A
peat core collected from the bog at Kotyk Lake (30 km NE of FF) shows declines in
206Pb/207Pb from the natural “background” values of 1.25 at the base of the core, to a
minimum of 1.02. A peat core collected from the bog at Sask Lake (88 km NW of FF) shows
declines in 206Pb/207Pb from the natural “background” values of 1.35 at the base of the core
to a minimum of 1.05. But the isotopic evolution of Pb shows significantly declines
in 206Pb/207Pb beginning in the late 1800’s, presumably because of long-range
atmospheric transport from other sources. The 206Pb/207Pb values increase in both
cores starting in the 1960’s, and reach a recent maximum in the 1990’s, apparently
reflecting the growing use and eventually phase out of leaded gasoline use. Since
the 1990’s, the 206Pb/207Pb have continued their decline, apparently reflecting the
elimination of leaded gasoline and the growing relative importance of Pb from the
smelter. The temporal evolution in Pb enrichment factors follows the history of
the metallurgical complex, with the maximum EF values (calculated using Sc)
reaching maxima of ca. 100 x (Kotyk Lake) and 10 x (Sask Lake). The maximum
rates of atmospheric Pb accumulation are approximately 1200 and 120 μg/m2/yr,
respectively.
In Finland, peat cores were taken from three bogs: the Pyhäsuo mire in SW Finland, 6 km NE
from the Cu Ni smelter at Harjavalta (HAR); at the Viurusuo complex in eastern
Finland, 8 km SW of the Cu Ni mine in the town of Outokumpu (OUT); and at
Hietajärvi (HJ), in the Patvinsuo National Park of eastern Finland. The cores from HJ
and OUT document 3,000 years of anthropogenic Pb and provide a remarkably
similar evolution of Pb isotopes, reaching values as low as 206Pb/207Pb = 1.151
(AD 1982) and 1.148 (AD 1984), respectively. At HAR, the minimum values are
lower (206Pb/207Pb = 1.120) and earlier (AD 1954 -1967), presumably because of
emissions from the smelter. The Pb concentrations in the porewaters from HAR are
approximately an order of magnitude greater than the other sites, and the 206Pb/207Pb values
significantly lower (ca. 1.12 vs. 1.15), because of the combined effects of greater
Pb deposition and surface water acidification (pH 3.5 versus pH 4.0 in the other
bogs). |
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