1. Metals analysis in tailings of Zaida abandoned mine,
Premier Workshop National sur la richesse des bassins sédimentaires:
Metals analysis in tailings of Zaida abandoned mine,
High Moulouya, Morocco
Meriem Laghlimi1, Bouamar Baghdad2, Hassan El Hadi1, Rachid Moussadek3 et Meryem Taoufik1
1- Université Hassan II Mohammédia, Faculté des Sciences Ben M’Sik/ Laboratoire de Géologie appliquée, Géomatique et Environnement, Casabalnaca, Maroc
2- Institut Agronomique et Vétérinaire Hassan II, Département des Ressources Naturelles et Environnement, Madinat El Irfane, Rabat, Maroc
3-Institut National de la Recherche Agronomique, BP 6356, Rabat, Maroc
Courriel :
Résumé
Matériels et Méthodes
The basin of Moulouya Oued is a region where mining industry has been developed early in the 20th century. As a consequence, residues generated from past mining activities over the years have been dumped as piles of tailings. Zaida is one of the most affected region in this basin because of lead mine exploitation for long time. The aim of this study is to determine the amount of trace elements and the contamination of the mineral sands.
Analysis of collected samples has been achieved using the ICP-AES analysis method. The samples, in form of powders, were enclosed in Teflon sheets.
The results show that the distribution of the studied metals (Pb, Zn, Cu, Cd, Cr and Ni) in the basin is dependent on location with a very significant contamination by Pb, Zn, Cu, Cd, Cr, and Ni close to the lead mine sites.
This study developed on tailings dumps and their surroundings, indicates the degree of contamination of the sands from the mining industry. The distribution of MTE highlighted the main contaminated areas.
Keywords : Environmental pollution, Moulouya Oued, Soils, Zaida mine, Trace elements.
Forty two soil samples were collected from a depth of about 0-20 cm. The soils were sampled using a plastic shovel and placed in clean plastic bags and stored at room temperature. The location of the sampled points is shown in Figure 1.
Analysis of physico-chemical parameters (pH, electrical conductivity, total calcium, phosphorus, potassium and organic matter) were conducted at the National Institute for Agricultural Research in Rabat.
Total heavy metal concentration (Pb, Co, Zn, Cu, Cd, Cr and Ni) was determined by ICP-AES (Inductive Coupled Plasma - Atomic Emission Spectroscopy). Samples were analyzed at the National Centre for scientific and technical studies of nuclear energy (CNESTEN) and the National Centre for Scientific and Technical Research in Rabat, Morocco.
Résultats
Table 1: Physico-chemical characteristics of soils in Zaida mine pH CE
μS/cm.
CACO3-
total% MO % P
mg/kg K+
Minimum
7,00
0,10
0,55
0,30
2,14
146,00
Average
8,16
0,31
39,04
1,26
19,37
299,62
Maximum
8,60
1,43
77,95
2,66
197,10
732,04
Zone d’étude
Table 2. Average, minimum and maximum contents (mg / kg) of heavy metals in soil samples Cd Co Cr Cu Ni Zn Pb
Minimum
0,03
0.38
0.01
0.11
0,13
0,36
Average
0,99
5,42
47,35
15,31
13,12
48,50
94,49
Maximum
3,00
20,40
777,20
77,2
48,90
206
830,95
[1]
0,35 - 30 90 35
[2]
5-80
20-300
2-200
[3]
0,05 -0,45
2 à 23
10 à 90
2 à 20
2 à 60
10 à 100
9 à 50
[4]
0,2 - 1 10 50
[1] Normes (Bowen, 1979) 
[2] Fleming et Parle, 1977 ; Alloway, 1990)
[3] Baize (1979) Sols ordinaires
[4] Alloway (1990)
All soil samples presented an alkaline ph, which ranged between 7 and 8.6;
Soils are poor in organic mater with a maximum value of 2,7%;
Heavy metal content of the Investigated soils are relatively high compared to uncontaminated soil standards ;
The heavy metal distribution is influenced by two factors: the distance from the tailings dam and the wind dispersion of sand particles;
Heavy metal contents decrease with increasing distance between the sampled points of tailings residue;
High levels of heavy metals were founded in the North East and South West direction, which correspond to the two predominant wind directions in this area.
Figure 1 Distribution of sampled points
Conclusion
Assessment of heavy metal soil contamination around tailings of Zaida abandoned mine showed that soils located near the tailings dam and those in the two main predominate directions of the winds in the regions have relatively high levels compared to the values of uncontaminated soil from the literature.
References
Alloway, B.J.,1990. Heavy metals in soils. 2nd Edition. Blackie and Son Ltd, Glasgow,
Baize, D. ,1997. Teneurs totales en éléments traces métalliques dans les sols (France). Références et stratégies d’interprétation, INRA Editions, Paris, 1997.
Bowen H.J.M. (1979). Environmental Chemistry of elements.Academic Press, New York, pp
Fleming, G. and Parle, P.,1977. Heavy metals in soils, herbage and vegetables from an industrialised area west of Dublin city. Irish Journal of Agricultural Research 16,
Zaida Mine