Heavy metal contamination from mining sites in South Morocco: 1. Use of a biotest to assess metal toxicity of tailings and soils.

Our work was conducted to investigate the heavy metal toxicity of tailings and soils collected from five metal mines located in the south of Morocco. We used the MetPAD biotest Kit which detects the toxicity specifically due to the heavy metals in environmental samples. This biotest initially developed to assess the toxicity of aquatic samples was adapted to the heterogeneous physico-chemical conditions of anthropogenic soils. Contrasted industrial soils were collected from four abandoned mines (A, B, C and E) and one mine (D) still active. The toxicity test was run concurrently with chemical analyses on the aqueous extracts of tailings materials and soils in order to assess the potential availability of heavy metals. Soil pH was variable, ranging from very acidic (pH 2.6) to alkaline values (pH 8.0-8.8). The tailings from polymetallic mines (B and D) contained very high concentrations of Zn (38,000-108,000 mg kg(-1)), Pb (20,412-30,100 mg kg(-1)), Cu (2,019-8,635 mg kg(-1)) and Cd (148-228 mg kg(-1)). Water-extractable metal concentrations (i.e., soil extracts) were much lower but were highly toxic as shown by the MetPAD test, except for soils from mines A, E and site C3 from mine C. The soil extracts from mine D were the most toxic amongst all the soils tested. On this site, the toxicity of soil water extracts was mainly due to high concentrations of Zn (785-1,753 mg l(-1)), Cu (1.8-82 mg l(-1)) and Cd (2.0-2.7 mg l(-1)). The general trend observed was an increase in metal toxicity measured by the biotest with increasing available metal contents in tailings materials and soils. Therefore, the MetPAD test can be used as a rapid and sensitive predictive tool to assess the heavy metal availability in soils highly contaminated by mining activities.

[1]  Impacts of Mine Drainage and Other Nonpoint Source Pollutants on Aquatic Biota in the Upper Powell River System, Virginia , 2003 .

[2]  S. M. Ullrich,et al.  Total and exchangeable concentrations of heavy metals in soils near Bytom, an area of Pb/Zn mining and smelting in Upper Silesia, Poland , 1999 .

[3]  M. He,et al.  Spatial and temporal patterns of acidity and heavy metals in predicting the potential for ecological impact on the Le An river polluted by acid mine drainage. , 1997, The Science of the total environment.

[4]  A. Kabata-Pendias.  Trace elements in soils and plants , 1984 .

[5]  G. Bitton,et al.  Evaluation of a microplate assay specific for heavy metal toxicity , 1994, Archives of environmental contamination and toxicology.

[6]  J. Morel,et al.  Heavy metal contamination from mining sites in South Morocco: 2. Assessment of metal accumulation and toxicity in plants. , 2006, Chemosphere.

[7]  M. Wong,et al.  Evaluation of major constraints to revegetation of lead/zinc mine tailings using bioassay techniques. , 2002, Chemosphere.

[8]  J. Morel,et al.  Measurement of in situ phytoextraction of zinc by spontaneous metallophytes growing on a former smelter site. , 2001, The Science of the total environment.

[9]  G. Ritchie,et al.  Calcium Chloride Extractable Cadmium as an Estimate of Cadmium Uptake by Subterranean Clover , 1991 .

[10]  Ivo Iavicoli,et al.  Evaluation of the environmental contamination at an abandoned mining site , 2002 .

[11]  J. Morel,et al.  A direct solid‐phase assay specific for heavy metal toxicity. I. methodology , 1996 .

[12]  J. Morel,et al.  Evolution en plein champ de la solubilité dans DTPA des métaux lourds du sol introduits par des épandages de boues urbaines chaulées , 1984 .

[13]  R. Sidle,et al.  Fate of Heavy Metals in an Abandoned Lead-Zinc Tailings Pond: II. Sediment , 1991 .

[14]  Wim Salomons,et al.  Environmental impact of metals derived from mining activities: Processes, predictions, prevention , 1995 .

[15]  I. Thornton,et al.  Hydrological and chemical factors controlling the concentrations of Fe, Cu, Zn and As in a river system contaminated by acid mine drainage , 1987 .

[16]  G. Bitton,et al.  MetPAD: A bioassay kit for the specific determination of heavy metal toxicity in sediments from hazardous waste sites , 1992 .

[17]  Nicholas F. Gray,et al.  Acid mine drainage composition and the implications for its impact on lotic systems , 1998 .

[18]  F. G. Bell,et al.  Environmental impacts associated with an abandoned mine in the Witbank Coalfield, South Africa , 2001 .

[19]  J. Morel,et al.  A direct solid‐phase assay specific for heavy‐metal toxicity. II. Assessment of heavy‐metal immobilization in soils and bioavailability to plants , 1996 .

[20]  A. P. Schwab,et al.  Bioavailability of zinc, cadmium, and lead in a metal-contaminated alluvial soil , 1993 .

[21]  W. Wenzel,et al.  Accumulation of heavy metals in plants grown on mineralised soils of the Austrian Alps , 1999 .

[22]  J. Morel,et al.  Assessment of metal accumulation in plants using MetPAD, a toxicity test specific for heavy metal toxicity , 2000 .

[23]  C. Williams,et al.  THE ACCUMULATION IN SOIL OF CADMIUM RESIDUES FROM PHOSPHATE FERTILIZERS AND THEIR EFFECT ON THE CADMIUM CONTENT OF PLANTS , 1976 .

[24]  M. Jung.  Heavy metal contamination of soils and waters in and around the Imcheon Au-Ag mine, Korea , 2001 .

[25]  D. Adriano.  Trace Elements in the Terrestrial Environment , 1986 .

[26]  J. Morel,et al.  Heavy metals in soils and plants of serpentine and industrial sites of Albania. , 1998, The Science of the total environment.

[27]  Ben Koopman,et al.  MetPADTM : a bioassay for rapid assessment of heavy metal toxicity in wastewater , 1992 .