Biogeochemical cycling of sulphur in karst and transfer into speleothem archives at Grotta di Ernesto, Italy

Peter M. Wynn, Andrea Borsato, Andy Baker, Silvia Frisia, Renza Miorandi, Ian J. Fairchild

    Research output: Contribution to journalArticlepeer-review

    24 Citations (Scopus)

    Abstract

    Trace amounts of sulphur in speleothems suggest that stalagmites may act as archives of sulphur deposition, thereby recording aspects of atmospheric variability in sulphur content. Accurate interpretation of this novel sulphur archive depends upon understanding how biogeochemical cycling in the soil and epikarst above the cave may modify the precursor atmospheric values of sulphur concentration and isotopic composition prior to incorporation into the speleothem record. Dual isotope analysis of δ34S-SO4 and δ18O-SO4 is used to trace biogeochemical transformations of atmospheric sulphur through the cave system at Grotta di Ernesto in the Italian Alps and builds towards a framework for interpretation of speleothem sulphur archives which depends on overlying ecosystem dynamics and karst hydrological properties. A three component model of atmospheric sulphate signal modification is proposed to be driven by (1). vegetation and soil cycling, (2). the degree of groundwater mixing in the karst aquifer; and (3). redox status. The relative influence of each process is specific to individual drip flow sites and associated stalagmites, rendering each sulphur archive a unique signal of environmental conditions. Under conditions found in the soil and epikarst above Grotta di Ernesto, the dual isotope signatures of sulphate sulphur and oxygen incorporated into speleothem carbonate, closely reflect past conditions of industrial sulphur loading to the atmosphere and the extent of signal modification through biogeochemical cycling and aquifer mixing.

    Original languageEnglish
    Pages (from-to)255-267
    Number of pages13
    JournalBiogeochemistry
    Volume114
    Issue number1-3
    DOIs
    Publication statusPublished - 2013

    Keywords

    • Biogeochemistry
    • Isotopes
    • Karst
    • Speleothem
    • Sulphur

    ASJC Scopus subject areas

    • Environmental Chemistry
    • Water Science and Technology
    • Earth-Surface Processes

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