Environmental Engineering Reference
In-Depth Information
(under empirical or experimental bases) may be followed. The main
difficulty, to implement this approach, is the selection of plants that can
establish and survive under mine wastes´ conditions. This chapter enlists
a group of plants, which have been able to establish in different Cd-
polluted mine residues, providing many options to use them with
remediation purposes. In addition, it considers the below-ground
microbial community relevant to plant establishment and growth under
these stressed conditions. It makes emphasis on the role played by soil
microorganisms with tolerance properties in the processes underlying
plant-based methods of remediation (phytoremediation) of heavy metal
contamination, including phytostabilization. It also shows that different
bacteria, with relevant characteristics for dealing with Cd, may be
isolated from the rhizosphere of these plants. Also, for instance, how
inoculation of
Echynocloa polystachya
with a
Pseudomonas
microbial
species increases Cd phytoaccumulation. The importance of the
extraradical mycelium of arbuscular mycorrhizal fungi and glomalin, a
glycoprotein produced by these fungi, in the sequestration of Cd is also
evidenced. In addition, the importance of these fungal structures in the
remediation of the mine residue and their participation in soil formation is
observed. In conclusion, it is suggested that in order to establish an
efficient low-cost remediation alternative, a combination of resources
might be used such as endemic plants and microorganisms, including
beneficial associations between them. In consequence, revegetated or
reestablished balanced ecosystems, which have been disturbed by mining
activities, may be obtained.
I
NTRODUCTION
Mining activities in Mexico have been carried out since early 1500
century (Le Riverend, 1989), when the Spanish people started ore minerals
extraction. Throughout centuries the residues have been accumulated in tailing
heaps (Carrillo-Chavez et al., 2003), it was not until recentrly that the
environmental regulation said that the hazards material should be isolated from
people. Nowadays, there are 15 states, (including more than 200
municipalities) in the all country, where the mining activity is one of the main
economical activities. During the last decade, the national environmental
ministry tried to encourage the application of regulations to control the
dispersion of these residues into the environment, and to use advanced
technology to manage the residues and disposal of them in safe conditions. For
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