F. Wisotzky

Publications (2)2.25 Total impact

• Article: Sequential extraction procedure in columns. Part 1: Development and description of a new method

  F. Wisotzky, N. Cremer
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  ABSTRACT: A sequential extraction procedure was carried out in columns using reagents that are known to be reliable from batch tests. The intention was to distinguish between different chemical forms of iron and heavy metals in samples from reduced porous aquifers, which demands anaerobic conditions for the extraction procedure and the determination of small amounts of reactive mineral phases in a quartz dominated sediment system. By means of the developed method, anaerobic conditions can be guaranteed in the columns, which could not be realized to full satisfaction in batch tests that were carried out in a glove box. In order to distinguish between the fractions that were water soluble, exchangeable, bound to carbonates and bound to hydroxides, different reagents were pumped through the sediments and sampled after passage of the columns. Sediment samples of 10kg each were investigated in this way. The extraction steps were known to be complete when analyses revealed that no further major and trace elements were leached out of the columns. This approach enabled well-adjusted amounts of reagents to be used. By means of the sequential extraction procedure in columns the composition of even small amounts of reactive mineral phases can be determined successfully, which contributes to a deeper understanding of the hydrogeochemical processes in aquifers. In batch tests this accuracy cannot be reached because of the surplus of the extraction solution in relation to the amount of sediment (higher solution-sediment ratio). Furthermore, larger samples are much more representative of the composition of the aquifers than smaller ones and the heterogeneity of the sediment does not limit the accuracy of the results as much as in batch tests. In addition, the technique of flushing sediment in a column is much more typical for the situation in an aquifer than suspending a few grams of a sample in the extracting reagents in batch extraction tests. In order to demonstrate the methodical improvements and field applications, the newly developed method was used to investigate the changing binding forms and mobility of iron and trace metals in samples from a lignite overburden dump, which are influenced by pyrite oxidation processes (acidification) followed by the addition of crushed limestone (neutralization) (see "Sequential extraction procedure in columns. Part2: Application of a new method").
  Environmental Geology 09/2003; 44(7):799-804. · 1.13 Impact Factor
• Article: Sequential extraction procedure in columns—part 2: application of a new method

  F. Wisotzky, N. Cremer
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  ABSTRACT: The binding forms of iron and trace elements (Ni, Co, As) in overburden dump sediments of the Rheinland lignite mining district in Germany were investigated by means of a newly developed sequential extraction procedure in columns (see part1: Development and description of a new method). The extraction tests aimed to prove the long-term immobilization of iron and heavy metals due to the addition of crushed limestone to the sediment in an effort to reduce the effects of pyrite oxidation reactions on the groundwater quality in lignite overburden dumps.Because of pyrite oxidation reactions the groundwater in the lignite overburden dumps will contain high concentrations of iron, heavy metals and sulfate at low pH values after the recovery of the groundwater level without taking measures against the acidification. In order to neutralize the acid and to limit the iron, sulfate and heavy metal mobility, crushed limestone is added to the sediment. The investigations aimed to determine the differences between the iron and trace metal binding forms in sediment samples with and without the addition of alkaline substances. The experimental set-up described in part1 could ensure anaerobic conditions as in the dumps and enabled the determination even of very small amounts of freshly precipitated mineral phases, which was necessary to identify the metal immobilizing processes under realistic conditions.In investigating the untreated overburden material, iron and heavy metals were mainly extracted from the water-soluble and exchangeable fraction, which means that they are highly mobile and will dissolve in the groundwater in high concentrations. The addition of crushed limestone causes the precipitation of iron carbonate and iron hydroxide mineral phases and the coprecipitation of the trace elements. Under the hydrochemical conditions that are present in the overburden dumps after the limestone addition, these phases are stable and act as an effective and long-term iron and trace element sink.
  Environmental Geology 01/2003; 44(7):805-810. · 1.13 Impact Factor