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 -