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Environmental
Techniques used
A variety of isotope systems have been used to assess and/or better
understand processes which impact on the health and quality of the
environment. Isotopes provide important advantages over standard
chemical techniques in cases where quantitative solutions are required.
Example Applications
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Tracing Pollution in Water Using Isotopes
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Rocks of different ages
and compositions have different isotope compositions which may be used as
tracers of pollution in water. Numerous studies utilising this have been
performed in South Africa, Namibia and Madagascar, particularly to identify
pollution contributions from different sources. The graph shown exhibits the
Sr and Pb isotope composition of water from the city of Johannesburg, South Africa, which
has been polluted by gold mining operations which started in 1886. In this case, reworking of the
old mine tailings dumps to recover residual gold was done using water cannon
(introduced water) that rapidly dissolved lead-bearing pyrite in the
tailings. This produced very acidic water that eroded the foundations of
factory buildings down slope and flow. The mining-related pollution was quite distinct
from natural ground water in the area and it was possible to show that at
least 90% of the polluted water corroding adjacent factory foundations was
introduced by the mining operations.
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The photograph above on the left
illustrates the effects of seepage of acid mine drainage through an earth
embankment at the boundary of a factory in the Johannesburg area (part of the
study illustrated above) whereas the photograph on the right is of fractures from
surface into shallow underground coal workings which spontaneously caught
fire. The burning coal exacerbates the acid mine drainage problem in this
area. Here too, water which has interacted with the coal has a distinctive
isotope signature which is different from that in other areas.
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Assessing the Source of Water Flowing into Mine Workings
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View of the open pit mine at Navachab, Namibia.
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Cross-section of the mine pit, illustrating the various stratigraphic
units which could be sources of water entering the mine workings.
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Water flowing into the open pit workings of the Navachab
gold mine in Namibia could come from a number of stratigraphic units, several
of which are karstic carbonates. However, the Sr isotope composition of water
in the various units differs, permitting one to identify the origin of the water.
In this case, water is derived from the footwall schist.
This project was performed in collaboration with
Dr Nick Steven of RockWater Consulting
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| Bruce Eglington. Saskatchewan Isotope Laboratory, Saskatoon, Canada
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