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| Titel |
Heavy metal pollution of soils and sediments at the historical smelting site of the Rudawy Janowickie Mountains (Lower Silesia, Poland). |
| VerfasserIn |
Jakub Kierczak, Catherine Néel, Anna Pietranik |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039522
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| Zusammenfassung |
| Multidisciplinary studies of historical slags are mostly focused on exploring how metallurgy
evolved through human history. Another purpose for studying historical slags are potentially
harmful interactions between slags, surrounding soils, sediments and waters. Metallurgical
slags generally concentrate potentially toxic elements (PTE) such as arsenic, copper and lead.
These elements may be mobilized and transferred into immediate surroundings. The main
aim of our work is to identify factors controlling migration of metals at the historical smelting
site of the Rudawy Janowickie Mountains. This study involves detailed analyzes of
historical slags (older than 300 years) containing PTE, as well as surrounding soils and
sediments.
The Rudawy Janowickie Mountains represented an important centre of copper mining
and smelting in Poland until 1925 with metallurgical activities being documented as
early as in the XIV century. The exploitation of Cu ores has left large amounts
of mine tailings and slags extending over ca. 35ha. The slags were deposited on
ground and no barriers between the slags and environment were set. Therefore, they
were continuously affected by variable factors, for example, changing weather
conditions.
Soils located in the study area are derived from granitic rocks. They are shallow (< 1
meter depth) and skeletic (containing > 50 wt. % of coarse fragments). Their pHw is acidic
and varies from 3.4 to 4.5 from the topsoil to the deeper horizons in which slags are
widespread. Mineral composition of soils and sediments is dominated by quartz, alkali
feldspar, plagioclase and biotite. However, some samples may contain additionally numerous
slag fragments.
At present, the slags occur within three types of environments: (1) at the surface, (2) in
soils and (3) in sediments from two streams: Janówka and Smelter Stream.
Studied slags were sampled in the vicinity of both streams from (1) surface, (2) soil
profiles and (3) streambeds. Furthermore, samples of soils and stream sediments were
collected at the same time in order to observe weathering features of slags in different
environments and to verify the influence of those wastes on properties of soils and
sediments.
Studied slags are isometric and well rounded (pebble-like), with size ranging from few to
dozens of centimetres. The average chemical composition of slags is 47 wt. %
Fe2O3, 40 wt. % SiO2, 8 wt. % Al2O3. Slags show elevated concentrations of Cu
(up to 13400 ppm), Zn (up to 3640 ppm), Pb (up to 270 ppm) and As (up to 130
ppm).
Dominant type of slag occurring in all environments is black and has massive
texture. It consists of silicate glass, fayalite, hercynite, bornite, pyrhotite, intermetallic
compounds of Fe and As, metallic Pb and Cu. Sulfides and metallic phases are
the most important PTE carriers. Second type of slag was found only on surface.
It is highly porous and often encloses small fragments of granitic rocks. Despite
weathered appearance, it has similar phase composition to the dominant type of slag.
The weathering products occur as aureoles and interstitial replacements within
the sulfides. Secondary phases in the aureoles are: brochantite, malachite and Fe
oxy-hydroxides.
PTE initially concentrated in primary phases such as sulfides can be mobilized by
weathering and be subsequently bounded in secondary phases (brochantite, malachite). The
stability of these phases depends on the surrounding conditions (e.g. here, secondary phases
are stable only in slags from surface). Presence of slags at the studied site is clearly
documented by geochemical analysis of stream sediments. The Cu concentration in
sediments from the area where no slags have been found is 8 ppm, while it exceeds 130 ppm
in the site where slags are widespread.
Our observations thus show that the studied slags release some potentially toxic elements
(especially Cu) during weathering and the slag texture appears to be an important factor
controlling metal migration.
The work was financed by Polish Ministry of Science and Higher Education grant no.
4269/PB/ING/09. |
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