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| Titel |
Geochemical tracing of As pollution in the Orbiel Valley (southern France): 87Sr/86Sr as a tracer of the anthropogenic arsenic in surface and groundwater. |
| VerfasserIn |
Mahmoud Khaska, Corinne Le Gal La Salle, Joël Lancelot, Patrick Verdoux, René Boutin |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250097658
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| Publikation (Nr.) |
 EGU/EGU2014-13260.pdf |
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| Zusammenfassung |
| The environmental impacts of arsenic mining activities and their effects on ecosystem and
human health are observed in many stream waters and groundwater. The aim of
this study is to identify the origin of As content in a mining environment using Sr
isotopes.
At the Salsigne gold mine, before the closure in 2004, high arsenic content has been observed
in surface water and groundwater in the Orbiel valley. At the site, immobilization of As, in As
rich leachate, is carried out by adding CaO. High contrast in 87Sr/86Sr between Arsenic rich
minerals associated with Variscan metamorphic rocks (0.714888-0.718835), together with
rich As waste water (0.713463-715477), and the CaO (0.707593) allows as to trace the origin
of anthropogenic As.
In 2012, Orbiel stream waters were sampled monthly upstream and downstream from the
ancient ore processing site and once after an important rainy event (117mm). The upstream
valley samples showed low and relatively constant As content with natural regional
background of 3.6 and 5.6 μg/L.
The rainy event induced only a slight increase in the As content up to 6.3 μg/L. High
87Sr/86Sr ratios suggested an influence of radiogenic Sr issued from the Variscan
metamorphic basement. Downstream from the area, the As content was at least10 time as
high. In the wet season, stream water As content clearly increased to 13.9-24 μg/L, reaching
120.5 μg/L during the rainy event. Associated 87Sr/86Sr ratio showed to be less radiogenic
(0.712276-0.714002). The anti correlation observed between As and 87Sr/86Sr suggest
that As issued from a natural origin is characterised by a high 87Sr/86Sr compared
to As derived from the CaO treatement used on site and characterized by a low
87Sr/86Sr ratio. During the dry season, increase in As content was observed reaching
110 μg/L. These highlights the contribution of alluvial groundwater to base flow,
probably associated with As reach leachate from the site. Contribution from the alluvial
aquifer is confirmed by results from redox potential (Eh) measurements in both
surface and groundwater. Hence, 87Sr/86Sr appears as an excellent tracer of the origin
of pollution associated with CaO treatment widely used in many water treatment
processes. |
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