Monika A. M. Kedziorek

Solubilization of lead and cadmium during the percolation of EDTA through a soil polluted by smelting activities

EDTA was percolated in laboratory columns through a soil polluted by heavy metals to investigate the efficiency of and processes involved in soil decontamination by chemical extraction. At high EDTA concentration (10−2 M), elution of Pb and Cd was very efficient for one pore volume, after which it decreased to almost zero due to depletion of available Pb and Cd and to competition with Ca and Fe slowly solubilized during the passage of the EDTA front. Clogging occurred after the end of the EDTA plateau. At lower EDTA concentrations (10−3 and 10−4 M), elution was less efficient, but extraction decreased little with the volume percolated; moreover no Ca above background values was dissolved. The optimum EDTA concentration for heavy metal extraction ranges between 10−2 and 10−3 M. The higher the concentration, the greater the extraction efficiency, but as the EDTA concentration is increased there is an optimum point at which clogging takes place and permeability decreases.

Acidification and solubilisation of heavy metals from single and dual-component model solids

Abstract The solubilisation of Ni, Cd and Pb from 3 model components of soils and sediments is investigated as a function of pH. In presence of increasing acidity, Ni, Cd and Pb are strongly solubilised from kaolinite and amorphous ferric hydroxide. Metal solubility tends to decrease, on the other hand, when humic acid is present. The quantity of metal solubilised from the dual-component, amorphous ferric hydroxide-humic acid system is smallest in the pH range 3.5 to 5.5. In the system kaolinite-humic acid, the solubility is highest at neutral pH. In these solid mixtures, metal solubility is always minimal (close to nil) in the pH range between the pHzpt of the humic acid and the pHzpt of the mineral solid. The solubilisation of heavy metals from soils and sediments is highly pH-dependent but does not always increase with decreasing pH. The solubility of Cd, Ni and Pb depends not only on pH but also on interactions between soil components.

Seasonal Cycles of Dissolved Cd, Mn and Zn in River Water Caused by Variations in pH Induced by Biological Activity

AbstractpH, dissolved oxygen, Zn, Cd and Mnwere measured once a month for 2.5 years in the LotRiver, France. The pH is controlled by biologicalactivity (photosynthesis and respiration). Dissolvedoxygen variations are due to a combination ofbiological activity and of the temperature dependenceof the oxygen solubility. pH is the master variablefor concentrations of aqueous Zn, Cd and Mn, thelowest concentrations being associated with thehighest pH values, which occur during the summer. pH-related processes rather than redox phenomenaexplain variations in dissolved Mn. Variations indissolved Zn and Cd are also controlled bypH-dependent reactions (possibly related to thedissolutive behavior of solid Mn).

Organic Matter as the Driving Force in the Solubilization of Fe and Mn During Riverbank Filtration

High-quality drinking water is a resource in high demand. Because of easy access and high productivity, alluvial aquifers can supply large quantities of drinking water. Water is pumped in the aquifer rather than directly in the river because it is generally assumed that filtration through the porous geological medium improves the quality of the water. Bank filtration either is the only treatment (usually in small communities) or serves as a pre-treatment (mostly in large urban areas) before the water is distributed to the consumer.

Modelling the mobility of pollutants away from waste disposal sites to the geosphere, a tool for optimal solid waste management

Abstract New regulations in the European Union regarding waste management will require a strong effort in modelling activities. Existing computer models which predict pollutant behaviour in geological environments are reviewed, and their potential use for the management of waste is discussed. The most promising of these are mechanistic models which account for pollutant behaviour in the context of a solution chemistry controlled by solid–water interactions. A major shortcoming of these computer codes is the lack of conceptual knowledge of the processes involved in interactions between wastes and water. Several needs are identified: better data bases (which must include the proper solubility-controlling variables), phenomenological understanding of pollutant behaviour in waste–leachate interactions, and model validation under realistic conditions.