Environmental Engineering Reference
In-Depth Information
instance, after the extraction of the concentrated mineral, the residues are
separated by the particles´ size in order to get stable tailing heaps with better
mechanic characteristics. In the country, there are only two sites for disposal
of hazardous wastes and there are few companies, legally recognized, for
managing hazardous residues. These facts made the management and disposal
of these residues very expensive. In addition, the huge volume of wastes
continuously produced, made it impossible to dispose of these residues under
conventional treatment. Rivero (1995) estimate a production of 337,500 tons
of tailing wastes every single day. 78 deposition sites, where the tailing is
exposed to the environmental condition, have been identified and some of
them have high Cd concentrations. Mining activities include the extraction of
Ag, Au, Cu, Zn, Pb and Fe. The extension of the soil surface polluted from
these sources is unknown, but in San Luis Potosi State Castro Larragoitia et al.
(1997) estimated a surface of 100 km
2
. In Guanajuato State, Carrillo-Chavez et
al. (2003) calculated 15 to 20 km
2
covered with low grade ore heaps and mine
waste materials.
Due to this situation, an alternative procedure to treat tailing heaps, which
have been deposited around the country is needed. The treatment should of
course be cheap and environmentally friendly. The mining companies are
clearly looking for inexpensive procedures to management their residues.
Among the promising techniques, phytoremediation has been proposed as
economically possible alternative, because, it requires low investment and the
expenses for maintenance are cheap. However, a selection of the plant species
able to grow under specific climatic and soil conditions ought to be done in
order to avoid the introduction of exotic or invasive plant species.
The aim of this research program has been to record and monitor tailing
heaps, in order to find accumulators and excluder plants species and the soil
microbes associated to their rhizosphere. In addition, to selecting the adapted
organisms to use them for improving soil revegetation.
M
INERAL
C
OMPOSITION AND
C
HARACTERISTICS
OF
T
AILINGS UNDER
S
TUDY
Some of the ore minerals extracted from the mining areas monitored are
showed in the Table 1. But, after the crunching, grinding and extraction of the
metals, the composition of the wastes is different from the original one.
Frequently, the residues deposited in each heap are a mixture of the wastes
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