Vol. 32 – 2006 - Ecologia Mediterranea

BOUAMAR BAGHDAD, MUSTAPHA NAIMI, ABDELHAK BOUABDLI, PHILIPPE SONNET, STANLEY LUTTS
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Introduction
The High Moulouya region is the most important
mining district in Morocco and has a long
history of mining which started early in the
20 th century. The High Moulouya region (Figure
1) forms the western margin of the eastern
meseta, which is made up of two Paleozoic
massifs whose setting caused the
formation of several major poly-metallic
deposits. The main ore mineral found in this
district are galena, blend, pyrite, limonite and
goethite (Emberger 1965).
The beginning of the 70s was marked by a
strong mining activity in Morocco. Lead was
among the most exploited metals with a production
over 170,000 tons of concentrated
ore, which represented about 3.5% of the lead
world production (Wadjinni 1998). In 1986,
Zaida mining center closed ten years after the
end of mining activities in the same time as
other main centers such as Mibladen and
Aouli. Presently, abandoned land mines are
evidenced by vast deteriorated and excavated
areas, piles of tailings, metallic residues and
ore washing waste. Not only the landscape
was affected, but also dumped mining
byproducts containing significant amounts of
Figure 1 – Geographic settings of the High Moulouya.
Figure 1 – Carte de situation.
heavy metals that can be easily dispersed,
washed and/or leached, creating an important
source of contamination downstream (Jung &
Thornton, 1996).
Very limited studies have addressed the issue
of contamination of the arid soils and the steppic
vegetation in the High Moulouya. Earlier
studies have focused almost exclusively on
water quality (Saidi et al. 2002; Bouabdli et
al. 2004, 2005; El Hachimi et al. 2005, 2006;
Baghdad et al. 2005, 2006).
The soil composition and its physicochemical
properties play a major environmental role as
it determines to a certain extent the metal levels
in plants. The relationship between the
concentration of MTE in soils and aboveground
vegetation was never investigated
before in this region. Vegetation in this area
consists in a typical semi-arid steppe with
patchy spatial distribution dominated by two
plant species: the perennial tussock grass
Stipa tenacissima L. and the dwarf shrub
Artemisia herba-alba Asso. Both plant
species are known to tolerate drought
throughout their cycle (Balaguer et al. 2002;
Salido et al. 2004) but data concerning heavy
metal resistance and accumulation are crucially
lacking.
The present work has been undertaken to
study the environmental impacts of mining
residues from the abandoned lead mine of
Zaida on soils and plants. This work was
intended to characterize the distribution of
lead, zinc and copper contaminants in soils
and vegetation after being leached from the
piles of tailings in order to assess aerial contamination
(by dust) and to understand the
mechanism of transfer of these MTE to the
soils and vegetation.
Materials and Methods
Ten samples (each containing at least 10 individual
plants) have been collected in the abandoned
lead mine of Zaida for each of the two
considered species (Figure 2): plants were
carefully removed from the soil in order to
maintain the root integrity. Root and shoot
systems were analysed separately. Roots were
gently washed in deionised water in order to
remove soil particle adhering to the roots.
Adjacent soil surface (0 to 10 cm) has been
sampled too. All soil and plant tissues have
been analysed to determine Pb, Cu and Zn
ecologia mediterranea – Vol. 32 – 2006