Heavy metal contamination from mining sites in South Morocco: Monitoring metal content and toxicity of soil runoff and groundwater |
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Authors: | Hicham El Khalil Ouafae El Hamiani Gabriel Bitton Naaila Ouazzani Ali Boularbah |
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Affiliation: | (1) Faculté des Sciences et Techniques Guéliz, Département de Biologie, Laboratoire Aliments, Environnement et Santé, Université Cadi Ayyad, Boulevard Abdelkrim Khattabi, BP 549, 40 000 Marrakech, Morocco;(2) Department of Environmental Engineering Sciences, University of Florida, Gainesville, FL 32611, USA;(3) Faculté des Sciences Semlalia, Département de Biologie, Laboratoire d’Hydrobiologie, Ecotoxicologie et Assainissement, Université Cadi Ayyad, BP 2390, 40 000 Marrakech, Morocco |
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Abstract: | The aim of the present work is the assessment of metal toxicity in runoff, in their contaminated soils and in the groundwater sampled from two mining areas in the region of Marrakech using a microbial bioassay MetPLATE™. This bioassay is based on the specific inhibition of the β-galactosidase enzyme of a mutant strain of Escherichia coli, by the metallic pollutants. The stream waters from all sampling stations in the two mines were all very toxic and displayed percent enzyme inhibition exceeding 87% except SWA4 and SWB1 stations in mine C. Their high concentrations of copper (Cu) and zinc (Zn) confirm the acute toxicity shown by MetPLATE. The pH of stream waters from mine B and C varied between 2.1 and 6.2 and was probably responsible for metal mobilization, suggesting a problem of acid mine drainage in these mining areas. The bioassay MetPLATE™ was also applied to mine tailings and to soils contaminated by the acidic waters. The results show that the high toxicity of these soils and tailings was mainly due to the relatively concentration of soluble Zn and Cu. The use of MetPLATE™ in groundwater toxicity testing shows that, most of the samples exhibited low metal toxicity (2.7–45.5% inhibition) except GW3 of the mine B (95.3% inhibition during the wet season and 82.9% inhibition during the dry season). This high toxicity is attributed to the higher than usual concentrations of Cu (189 μg Cu l−1) and Zn (1505 μg Zn l−1). These results show the potential risk of the contamination of different ecosystems situated to the vicinity of these two metalliferous sites. The general trend observed was an increase in metal toxicity measured by the MetPLATE with increasing total and mobile metal concentrations in the studied matrices. Therefore, the MetPLATE bioassay is a reliable and fast bioassay to estimate the metals toxicity in the aquatic and solids samples. |
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Keywords: | Groundwater Heavy metals Metal toxicity testing MetPLATE™ Mining sites Soil runoff |
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