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