The present work assesses the temporal distribution pattern and geochemical changes of rare earth elements and Yttrium, Scandium, Thorium, and Uranium delivery into the Oualidia lagoon. Two sediment cores were retriev...The present work assesses the temporal distribution pattern and geochemical changes of rare earth elements and Yttrium, Scandium, Thorium, and Uranium delivery into the Oualidia lagoon. Two sediment cores were retrieved from the Oualidia lagoon and analyzed using neutron activation analysis. The results indicated that heavy rare earth elements are slightly enriched the sediment cores over light rare earth elements. The highest values of REEs were recorded in the top layers of the cores and depleted with depth, suggesting a possible change in factors controlling their accumulation, including mechanical, chemical, and environmental parameters such as weathering intensity, grain size, and Fe-Mn oxides. The sediments display positive Ce anomalies, which are probably related to the submarine weathering process and detrital input. Noting also the variation of hydrodynamics conditions and confinement of the upstream part of the lagoon played a key role in changing the sediment origins.Thus, further investigation of REEs origin in the Oualidia lagoon sediment is required to identify their sources,provenances, and the factors controlling their spatial and vertical distributions. However, these results provide baseline data of occurring changes in REEs geochemical composition and constitute a typical study case to understand the link between sedimentary and geochemistry processes in a lagoonal ecosystem.展开更多
A local case study for the environmental impact of landfill leachate on groundwater quality along and across the Mediouna landfill is presented, based on physicochemical and statistical approaches. The landfill has be...A local case study for the environmental impact of landfill leachate on groundwater quality along and across the Mediouna landfill is presented, based on physicochemical and statistical approaches. The landfill has been operational since 1986 and it receives municipal solid wastes produced by the city of Casablanca, whose the daily waste output exceeds 4000 t. This waste is stockpiled in old sandstone quarries;the site has never been sealed before its opening. The aim of this study is to update the knowledge about groundwater quality around the landfill, to determine the factors controlling the extent of groundwater contamination and compare the results with those of 1989 and 2001. To evaluate groundwater pollution due to this landfill, piezometric level and geochemical analyses have been carried out on 19 wells. The physicochemical data of groundwater down-gradient of the landfill site is showing a deterioration of its quality, to the point that the wells have become unusable. The statistical treatment of physicochemical data by principal components analysis allowed the mapping of three areas downstream of the landfill. The first is hardly polluted, the second is moderately polluted and the third is characterized by mineralization through their waters and the almost absence of organic matter. The extent of groundwater contamination from an area with a radius of 200 m in 1989, to an area with a radius of about 1 km in 2001 to more 2 km as of today. This extension is controlled by the structural factor of faults, by the lithology of aquiferous and the intensity of water pumping;the wells equipped with pumps exert pressure against the advanced front of the pollution.展开更多
The Casablanca landfill is one among many uncontrolled dumping sites in Morocco with no bottom liner. About 4000 tons/day of solid wastes from mixed urban and industrial origins are placed directly on the fifteen old ...The Casablanca landfill is one among many uncontrolled dumping sites in Morocco with no bottom liner. About 4000 tons/day of solid wastes from mixed urban and industrial origins are placed directly on the fifteen old sandstone quarries. At the site of this landfill, the groundwaters circulate deeply (10 m) in the fractured aquiferous quartzites, the site has never been sealed before its opening. The aim of this study is the characterization the groundwater quality around the landfill, to delimit the contaminated zone and the factors controlling the extent of groundwater contamination. To evaluate groundwater pollution due to this landfill, piezometric level and geochemical analyses have been carried out on 19 wells. The results of geochemical analyses show an important qualitative degradation of the groundwater, especially in the parts situated in the down gradient area and in direct proximity to the landfill. In these polluted zones, we have observed the following values: higher than 11 mS/cm in electric conductivity, 1400 mg/L in bicarbonates, 275 mg/L in chemical oxygen demand, 2616 and 100 mg/L respectively in chlorides and sulfate, 269.5 mg/L in nitrates, 50 - 100 mg/L in cadmium, and 40 - 230 μg/L in chromium. These concentrations widely exceed the standard values for potable and irrigation water. Several determining factors in the evolution of groundwater contamination have been highlighted, such as: depth of the water table, permeability of unsaturated zone and lineaments, effective infiltration, absence of a system for leachate drainage. So, to reduce the pollution risks of the groundwater, it is necessary to set a system of collection, drainage and treatment of landfill leachates and to emplace an impermeable surface at the site of landfill, in order to limit the infiltration of leachate.展开更多
文摘The present work assesses the temporal distribution pattern and geochemical changes of rare earth elements and Yttrium, Scandium, Thorium, and Uranium delivery into the Oualidia lagoon. Two sediment cores were retrieved from the Oualidia lagoon and analyzed using neutron activation analysis. The results indicated that heavy rare earth elements are slightly enriched the sediment cores over light rare earth elements. The highest values of REEs were recorded in the top layers of the cores and depleted with depth, suggesting a possible change in factors controlling their accumulation, including mechanical, chemical, and environmental parameters such as weathering intensity, grain size, and Fe-Mn oxides. The sediments display positive Ce anomalies, which are probably related to the submarine weathering process and detrital input. Noting also the variation of hydrodynamics conditions and confinement of the upstream part of the lagoon played a key role in changing the sediment origins.Thus, further investigation of REEs origin in the Oualidia lagoon sediment is required to identify their sources,provenances, and the factors controlling their spatial and vertical distributions. However, these results provide baseline data of occurring changes in REEs geochemical composition and constitute a typical study case to understand the link between sedimentary and geochemistry processes in a lagoonal ecosystem.
文摘A local case study for the environmental impact of landfill leachate on groundwater quality along and across the Mediouna landfill is presented, based on physicochemical and statistical approaches. The landfill has been operational since 1986 and it receives municipal solid wastes produced by the city of Casablanca, whose the daily waste output exceeds 4000 t. This waste is stockpiled in old sandstone quarries;the site has never been sealed before its opening. The aim of this study is to update the knowledge about groundwater quality around the landfill, to determine the factors controlling the extent of groundwater contamination and compare the results with those of 1989 and 2001. To evaluate groundwater pollution due to this landfill, piezometric level and geochemical analyses have been carried out on 19 wells. The physicochemical data of groundwater down-gradient of the landfill site is showing a deterioration of its quality, to the point that the wells have become unusable. The statistical treatment of physicochemical data by principal components analysis allowed the mapping of three areas downstream of the landfill. The first is hardly polluted, the second is moderately polluted and the third is characterized by mineralization through their waters and the almost absence of organic matter. The extent of groundwater contamination from an area with a radius of 200 m in 1989, to an area with a radius of about 1 km in 2001 to more 2 km as of today. This extension is controlled by the structural factor of faults, by the lithology of aquiferous and the intensity of water pumping;the wells equipped with pumps exert pressure against the advanced front of the pollution.
文摘The Casablanca landfill is one among many uncontrolled dumping sites in Morocco with no bottom liner. About 4000 tons/day of solid wastes from mixed urban and industrial origins are placed directly on the fifteen old sandstone quarries. At the site of this landfill, the groundwaters circulate deeply (10 m) in the fractured aquiferous quartzites, the site has never been sealed before its opening. The aim of this study is the characterization the groundwater quality around the landfill, to delimit the contaminated zone and the factors controlling the extent of groundwater contamination. To evaluate groundwater pollution due to this landfill, piezometric level and geochemical analyses have been carried out on 19 wells. The results of geochemical analyses show an important qualitative degradation of the groundwater, especially in the parts situated in the down gradient area and in direct proximity to the landfill. In these polluted zones, we have observed the following values: higher than 11 mS/cm in electric conductivity, 1400 mg/L in bicarbonates, 275 mg/L in chemical oxygen demand, 2616 and 100 mg/L respectively in chlorides and sulfate, 269.5 mg/L in nitrates, 50 - 100 mg/L in cadmium, and 40 - 230 μg/L in chromium. These concentrations widely exceed the standard values for potable and irrigation water. Several determining factors in the evolution of groundwater contamination have been highlighted, such as: depth of the water table, permeability of unsaturated zone and lineaments, effective infiltration, absence of a system for leachate drainage. So, to reduce the pollution risks of the groundwater, it is necessary to set a system of collection, drainage and treatment of landfill leachates and to emplace an impermeable surface at the site of landfill, in order to limit the infiltration of leachate.
