Heavy metal contamination from mining sites in South Morocco: Monitoring metal content and toxicity of soil runoff and groundwater

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 beta-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 microg Cu l(-1)) and Zn (1505 microg 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.

Acid Mine Drainage at the Abandoned Kettara Mine (Morocco): 1. Environmental Characterization

“…2) and the water and soil are polluted. Ground water sampled from wells at the mine had high concentrations of SO 4 (1,300 mg/L); the metal content of the soil exceeded European standards (El Khalil et al 2007). …”

Bioinformatic and Expression Analyses of Genes Mediating Zinc Homeostasis inNostoc punctiforme

“…Considerably less information is available in relation to the longer-term effects of heavy metal treatment and the capacity of cyanobacteria to actively accumulate, retain and efflux heavy metals, since previous studies have focused on short exposures, commonly 1 h (24), 2 h (45), and 6 h (34). The present study shows that N. punctiforme can tolerate a maximum ZnCl 2 concentration of 22 M over a 14-day period and that cell numbers were significantly reduced in ZnCl 2 treatments of Ͼ22 M. This is not a high threshold compared to zinc concentrations in contaminated waters, which can exceed 500 mg liter Ϫ1 (2,13,46 65 Zn studies, where Zn 2ϩ influx increased over a period of 3 days and then stabilized. In contrast efflux from preloaded cells occurred more rapidly in the first 3 h and then remained unchanged for 6 days.…”

Perceptions du développement minier durable par les acteurs locaux, gouvernementaux et industriels au Maroc /

“…De grandes masses de rejets riches en sulfures, qui libèrent en s'oxydant des eaux acides fortement chargées en métaux, ont été disposées en surface sans aucun traitement, ce qui peut affecter gravement la santé du public (Boularbah et al, 2006a,b;El Khalil et al, 2008;Hakkou et al, 2008). À l'époque de l'exploitation de la mine de Kettara, ni les attentes de la communauté ni les normes de protection de l'environnement n'étaient aussi élevées qu'elles le sont aujourd'hui.…”