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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Isotopic archives of sulphate in speleothems.
AU - Wynn, Peter M.
AU - Fairchild, Ian J.
AU - Baker, Andy
AU - Baldini, James U. L.
AU - McDermott, Frank
N1 - The final, definitive version of this article has been published in the Journal, Geochimica et Cosmochimica Acta 72 (10), 2008, © ELSEVIER.
PY - 2008/5/15
Y1 - 2008/5/15
N2 - The hemispheric impact of industrial emissions upon atmospheric sulphur loading is reflected in the sulphur depositional history recorded in cores from ice sheets. However, these do not reveal regional variations. Recently deposited speleothems are used here as archives of regional sulphur depositional history at two locations within the United Kingdom and Ireland. δ34S-so4 and δ18O-so4 present within speleothem carbonate are measured for the first time as part of a dual isotope approach to decode the speleothem sulphur record. The largely refractory nature of δ34S-so4 under oxidising conditions enables source provenance of atmospheric SO2, whereas the complex cycles of isotopic exchange and fractionation during incorporation of oxygen into sulphate molecules enable δ18O-so4 signatures to yield insights into ambient environmental conditions and biogeochemical cycling in the ecosystem above the cave. δ34S-so4 values extracted from speleothem carbonate formed within Browns Folly Mine, UK, range from +3.5 to +5.5‰ and δ18O-so4 +10.3 to +13.7‰. Both signatures lie within the range expected from sulphate deposition in industrial locations and reflect the transfer of sulphate into speleothem calcite with little fractionation. However, δ18O-so4 signatures at Crag Cave, western Ireland, are isotopically heavier than expected and approach isotopic equilibrium with δ18O-h2o under reducing conditions. Dual isotope analysis of δ34S-so4 and δ18O-so4 optimises the correct identification of sulphur sources and biogeochemical cycling prior to incorporation into the speleothem record. At carefully selected cave sites where drip water flowpaths into the cave remain oxic, speleothems hold the potential to retain records of atmospheric sulphur loading at the local and regional scale.
AB - The hemispheric impact of industrial emissions upon atmospheric sulphur loading is reflected in the sulphur depositional history recorded in cores from ice sheets. However, these do not reveal regional variations. Recently deposited speleothems are used here as archives of regional sulphur depositional history at two locations within the United Kingdom and Ireland. δ34S-so4 and δ18O-so4 present within speleothem carbonate are measured for the first time as part of a dual isotope approach to decode the speleothem sulphur record. The largely refractory nature of δ34S-so4 under oxidising conditions enables source provenance of atmospheric SO2, whereas the complex cycles of isotopic exchange and fractionation during incorporation of oxygen into sulphate molecules enable δ18O-so4 signatures to yield insights into ambient environmental conditions and biogeochemical cycling in the ecosystem above the cave. δ34S-so4 values extracted from speleothem carbonate formed within Browns Folly Mine, UK, range from +3.5 to +5.5‰ and δ18O-so4 +10.3 to +13.7‰. Both signatures lie within the range expected from sulphate deposition in industrial locations and reflect the transfer of sulphate into speleothem calcite with little fractionation. However, δ18O-so4 signatures at Crag Cave, western Ireland, are isotopically heavier than expected and approach isotopic equilibrium with δ18O-h2o under reducing conditions. Dual isotope analysis of δ34S-so4 and δ18O-so4 optimises the correct identification of sulphur sources and biogeochemical cycling prior to incorporation into the speleothem record. At carefully selected cave sites where drip water flowpaths into the cave remain oxic, speleothems hold the potential to retain records of atmospheric sulphur loading at the local and regional scale.
KW - Sulphur isotopes
KW - Sulphate-oxygen isotopes
KW - speleothems
KW - atmospheric sulphur
UR - http://www.scopus.com/inward/record.url?scp=43449108250&partnerID=8YFLogxK
U2 - 10.1016/j.gca.2008.03.002
DO - 10.1016/j.gca.2008.03.002
M3 - Journal article
VL - 72
SP - 2465
EP - 2477
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
SN - 0016-7037
IS - 10
ER -