Wolfgang Calmano

Chemical extraction of heavy metals in polluted river sediments in central Europe

Abstract A five-step sequential extraction technique was used to determine the chemical association of heavy metals (Zn, Cd, Pb, Cu) with major sedimentary phases (exchangeable cations, easily and moderately-reducible compounds, organic/sulfidic phases, residual components) in samples from polluted rivers in Central Europe (Middle Rhine River, Lower Rhine/Rotterdam Harbor, Weser Estuary, Neckar River). Data gained suggest that the surplus of metal contaminants introduced into the aquatic system from anthropogenic sources usually exists in relatively unstable chemical forms. The more important accumulative phases for trace metals are found in the easily-reducible fractions. Extraction with acidified hydroxylamine solution seems to yield the metal fractions which may predominantly participate in short-term geochemical and biochemical processes. Rates of mobilization were significantly higher for zinc and cadmium than for copper and lead.

EVALUATION OF A LEACHING PROCESS COUPLED WITH REGENERATION/RECYCLING OF THE EXTRACTANT FOR TREATMENT OF HEAVY METAL CONTAMINATED SOLIDS

A hydrometallurgical circuit process combining the leaching of metals with the electrolytic regeneration of the mass separating agent is an option to effectively treat heavy metal contaminated solids. This process aims towards a closed loop utilisation of the extractant by its regeneration and recycling, enabling the use of high cost extractants and the recovery of the heavy metals as well. The circuit process, in which each cycle consists of an extraction step followed by the electrolytic regeneration of the mass separating agent and a second extraction to finally recycle the separating agent and start a new cycle, was applied on a lead contaminated soil from an accumulator manufacturing facility and for the removal of copper from a municipal solid waste incinerator bottom ash. For the first case a 0.13 M citrate solution was used at a pH of 5; for the second 10% sulphuric acid (pH=0.5). The results showed that above 80% of lead and copper were removed from soil and ash, respectively, when the concentration of mass separating agent was controlled and kept constant. The extraction efficiency of metals from the solid materials was in the same range as the one obtained by two extraction steps using fresh extracting agent. However, due to losses of the mass separating agent the operation in a complete closed loop configuration was not possible. Nevertheless, a substantial reduction in separating agent consumption was achieved. The process proved to be suitable for treating highly contaminated materials, for which the operation parameters of extraction and regeneration are more favourable, also increasing the recovery of metals.

Chemical mobility and bioavailability of sediment-bound heavy metals influenced by salinity

The transfer of metals from contaminated sediments to algal cell walls (Scenedesmus quadricauda) and organisms from various trophic levels (euryhaline osmoconform hydroid Cordylophora caspia and algae Brachiomonas submarina) was studied with a multichamber device. The system consists of a central chamber which contained the mud suspension and six external chambers containing the different biological indicators. The solids in the central and external chambers are separated by 0.45 µm-diameter membranes which allow diffusion of the mobilized, dissolved metal compounds. Experiments were performed with dredged sediments at various salinities (0.5, 1.0, 1.5, and 2.0 percent, respectively) and the kinetic of re-adsorption was obtained by taking samples after different time intervals. High enrichment of Cd was found in the living alga Brachiomonas submarina, but on the other side only a weak influence of salinity on re-adsorption could be observed. Model experiments with ionic Cd showed a clear dependency on Cd-sorption on the algae, Cd-concentration in solution, and salinity. These results indicate that the transfer of metals mainly depends on the specific surface properties of the substrates and on the specific chemical form of the dissolved mobilized metal.

Detoxification of tributyltin contaminated sediments by an electrochemical process

Preliminary experiments have shown that dibutyl and tributyltin can be decomposed by the electrochemical treatment of sediment. Two different process pathways have been described and compared. A slurry electrolysis of the suspended sediment seemed to be more efficient than column leaching followed by electrolysis. Tributyltin was destroyed under oxidising as well as under reducing process conditions. The detoxification mechanism seemed to be stepwise removal of the butyl groups. A partial debutylation of tri- and dibutyltin could be achieved, although monobutyltin was not affected. This technique is promising, but further investigation is necessary to improve the experimental conditions and to characterise the real potential of these process pathways.

Reduction of tributyltin (TBT) and other organic pollutants of concern in contaminated sediments by means of an electrochemical oxidation

In contaminated sediments butyltin compounds and PAH can be diminished by means of an electrochemical treatment. The butyltin concentrations of the fine fraction (particle size <20 pm) of a mechanical separation unit were reduced from 350 pg/kg to < 10 μg/kg for tetrabutyltin (TeBT), from 2600 μg/kg to <30 μg/kg for tributyltin (TBT), 380 pg/kg to <100 pg/kg for dibutyltin (DBT), and from 570 pg/kg to <100 μg/kg for monobutyltin (MBT), respectively. Furthermore the sum of PAH concentrations for 16 PAH descended approximately 90% during a residence time in the electrolysis cell of 3 h, while in contrast PCB concentrations remained the same before and after the treatment. Apparently, the presence of PCB limited the application of this process, if the initial concentration exceeded guideline values for relocation. Further investigations have to be undertaken to clarify this point. Nevertheless the promising results obtained from a technical treatment unit have led to the construction of a pilot plant, which is installed in Bremen and operating since the beginning of 2002.

Comparison of five bioassay techniques for assessing sediment-bound contaminants

Biological response could not be predicted based on chemical concentration of the sediment contaminants. Bioassays integrate the response of test organisms to contaminants and nutrients. Comparative results of five acute bioassays indicated that Neubauer phytoassay was the most sensitive. The microbial biomass and algal growth tests indicated a response to the availability of contaminants and nutrients. These results suggest the usefulness of a diversity of bioassays in toxicity testing of sediment contamination.

Comment on the German Draft Legislation on Hydraulic Fracturing: The Need for an Accurate State of Knowledge and for Independent Scientific Research

The Need for an Accurate State of Knowledge and for Independent Scientific Research Martin Elsner,*,† Kathrin Schreglmann,† Wolfgang Calmano,‡ Axel Bergmann, Andrea Vieth-Hillebrand, Franziska D. H. Wilke, Klaus-Michael Wollin, Anett Georgi, Winfried Schmidt, Thilo Hofmann, Vesna Micic, Avner Vengosh, and Bernhard Mayer †Helmholtz Zentrum Munchen, Institute of Groundwater Ecology, Ingolstadter Landstrasse 1, 85764 Neuherberg, Germany ‡Hamburg University of Technology, Institute of Environmental Technology and Energy Economics, Harburger Schlossstrasse 36, 21079 Hamburg, Germany IWW Zentrum Wasser, Moritzstrasse 26, 45476 Mulheim an der Ruhr, Germany Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany Lower Saxony Governmental Institute of Public Health, Roesebeckstrasse 4-6, D 30449 Hannover, Germany Helmholtz Center for Environmental Research UFZ, Department of Environmental Engineering, Permoserstrasse 15, 04318 Leipzig, Germany Westfalische Hochschule, University of Applied Sciences, Neidenburger Strasse10, D-45877 Gelsenkirchen, Germany Department of Environmental Geosciences, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, North Carolina 27708, United States Department of Geoscience, University of Calgary, Calgary, Alberta Canada T2N 1N4

Cellulose Acetate Reverse Osmosis Membranes Made by Phase Inversion Method: Effects of a Shear Treatment Applied to the Casting Solution on the Membrane Structure and Performance

A mixture of equal parts of cellulose diacetate and cellulose triacetate was dissolved in dipropylene glycol and exposed to shear stresses of varying intensity on a three-roll calander. Asymmetric reverse osmosis membranes were prepared from these materials by the phase-inversion method. Reverse osmosis tests in a dead-end module provided membrane performance data. A structure analysis was performed by scanning electron microscopy and the microstructure of the membranes was investigated by differential scanning calorimetry and X-ray diffraction. It was observed that increasing shear times as well as shear rates reduced the salt rejection while the permeate flux was escalating. The size-exclusion chromatography analysis showed a strong decrease of M w and M z at a constant M n indicating the degradation of the higher molar mass macromolecules. Since the physical structure of the membranes was not affected and a change in polymorphism could not be related to the variations in the reverse osmosis performance the reduced salt rejection should be caused by this degradation process, supposedly through affecting the materials diffusion properties by changing the fractional free volume.

Direktbestimmung von Cd, Cu und Ni im Elbeästuar mit Hilfe der Zeeman-Atomabsorptionsspektroskopie und Matrixmodifikation

Es werden Verfahren zur Direktbestimmung von Cd, Cu und Ni im Elbeastuar vorgestellt, die auf Zeeman-Untergrundkorrektur und Matrixmodifikation beruhen.

Interactions of organic pollutants with soil constituents in aqueous and oil-contaminated systems

Different soil samples and synthetic goethite were reacted with γ-HCH, anthracene, 2,4-D and atrazine in a solid/water and a solid/oil system. The non-polar compounds γ-HCH and anthracene were only sorbed from aqueous solution, in particular by soil samples with a high content of organic carbon. When dissolved in oil these non-polar compounds were not sorbed by any of the soil samples investigated. For atrazine, little sorption was observed whereas for 2,4-D, sorption from the oil phase was much higher than from aqueous solution. This effect is probably connected to modifications of the electric double layer on the particle surfaces.