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| Titel |
Processes and fluxes during the initial stage of acid sulfate soil formation |
| VerfasserIn |
J. Gröger, K. Hamer, H. D. Schulz  |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029534
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| Zusammenfassung |
| Acid sulfate soils occur over a wide range of climatic zones, mainly in coastal landscapes. In
these soils, the release of sulfuric acid by the oxidation of pyrite generates a very
acidic environment (e.g., DENT and PONS, 1995, PONS, 1973). Two major types
of acid sulfate soils can be distinguished: In actual acid sulfate soils, the initially
contained pyrite was at least partly oxidized. This resulted in a severe acidification
of the soil. Potential acid sulfate soils are generally unoxidized and contain large
amounts of pyrite. Upon oxidation, these soils will turn into actual acid sulfate soils.
By excavation or lowering of the groundwater table, potential acid sulfate soils
can be exposed to atmospheric oxygen. During oxidation the pH drops sharply
to values below pH 4. This acidification promotes the release of various metals,
e.g., alumina, iron and heavy metals. Additionally, large quantities of sulfate are
released.
In order to assess the effects of disturbances of potential acid sulfate soils, for example by
excavations during construction works, several large scale column experiments were
conducted with various types of potential acid sulfate soils from Northern Germany. In these
experiments, the oxidation and initial profile development of pyritic fen peats and thionic
fluvisols were studied over a period of 14 months. The study focused on leaching and the
translocation of various metals in the soil profile. To study mobilization processes, element
fluxes and the progress of acidification, soil water and leachate were analyzed for total
element concentrations. Furthermore, several redox-sensitive parameters, e.g., Fe2+ and
sulfide, were measured and changes to the initial solid phase composition were analyzed.
Chemical equilibria calculations of the soil water were used to gain insights into precipitation
processes of secondary products of pyrite oxidation and leaching products. The results
of this study will support the assessment of risks deriving from acid sulfate soils.
Furthermore, these experiments can serve as a model for the initial stage of naturally
occurring acid sulfate soil formation. Thus, the results will provide a base for the
interpretation of element distribution in the solid phase of natural acid sulfate soil
profiles.
References
DENT, D. L. and PONS, L. J. (1995) A world perspective on acid sulphate soils. Geoderma
67, 263-276.
PONS, L. J. (1973) Outline of genesis, characteristics, classification and improvement of
acid sulphate soils. In Acid Sulphate Soils - Proceedings of the International Symposium on
Acid Sulphate Soils - I Introductory Papers and Bibliography (ed. H. Dost). pp.
3-27 |
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