HR: 17:00h
AN: B44C-04    [Abstracts]
TI: Atmospheric Sulphur Archives in Tree Rings: a First Comparison With Speleothems
AU: * Fairchild, I J
EM: i.j.fairchild@bham.ac.uk
AF: University of Birmingham, School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom
AU: Wynn, P M
EM: p.m.wynn@bham.ac.uk
AF: University of Birmingham, School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom
AU: Baker, A
AF: University of Birmingham, School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom
AU: Hartland, A
AF: University of Birmingham, School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom
AU: Loader, N J
AF: University of Swansea, Department of Geography, Swansea University, Swansea, SA2 8PP, United Kingdom
AU: Lageard, J A
AF: Manchester Metropolitan University, Department of Environmental & Geographical Sciences, Manchester Metropolitan University, Manchester, M1 5GD, United Kingdom
AU: Thomas, P
AF: Keele University, School of Life Sciences, Keele University, Staffordshire, ST5 5BG, United Kingdom
AU: Frisia, S
AF: University of Newcastle, School of Environmental and Life Sciences, University of Newcastle, Callaghan, Newcastle, NSW 2308, Australia
AU: Susini, J
AF: ESRF, European Synchrotron Radiation Facility, Grenoble, F-38043, France
AB: The high atmospheric loading of sulphur pollutants during the 20th century is recorded in archives such as ice cores, archived soils, and some peats. In karstic settings, both trees and speleothems offer proxy records capable of encoding environmental information and our work demonstrates how sulphur is encoded in these archives. Recent work by others (Kawamura et al., 2005, Environmental Science and Technology) on two Japanese tree species has demonstrated that they preserve S concentration and isotopic archives broadly consistent with 20th century atmospheric variations. Frisia et al. (2005, Earth and Planetary Science Letters) first demonstrated the preservation of secular atmospheric sulphur records as carbonate-associated sulphate (CAS) in speleothem calcite, but at the forested alpine Ernesto site (NE Italy) it was noted that there was a lagged response in the speleothem compared with the atmosphere. Our new study of sulphur and oxygen isotopes in sulphate in atmospheric precipitation and cave dripwaters demonstrates that this lag is associated with the mineralization of sulphate in organic form followed by re-oxidation to sulphate leading to a resetting of the sulphate oxygen signal. The speleothems themselves show pronounced annual cycles in sulphate, despite the constant level of sulphate in dripwater. New experiments on sulphate incorporation in calcite precipitated at rates comparable to those in the cave system demonstrates that the main control is the pH of the system, which is modulated by seasonal variations in the PCO2 of the cave air. A study of S distribution and concentration within two tree species Picea abies and Abies alba from close to the Ernesto site has been made by a combination of synchrotron micro-XRF and NEXAFS and high mass-resolution ICP-MS analysis. Resin was removed from the tree samples before analysis since it is likely to be associated with element mobility. XRF mapping clearly demonstrates enhanced levels of S in the primary cell wall, where it is likely to be associated with proteins, and hence that it is likely to remain fixed over time, since this layer is overlain by a thicker secondary layer of carbohydrates (cellulose and lignins). Abies alba has the higher S concentrations (50-100 ppm in bulk wood) and these increase during the 20th century. Pronounced annual variations observed in synchrotron analyses largely reflect changes in wood density since bulk ICP-MS analyses show relatively little difference between early and late wood of the annual cycle. NEXAFS analyses demonstrate the occurrence of S in a mixture of oxidation states, primarily 0 to +1, +2, +5 and +6. We predict that S isotope analysis of the tree rings will preserve that of the soil S pool at the time of tree growth.
DE: 0419 Biomineralization
DE: 0486 Soils/pedology (1865)
DE: 0488 Sulfur cycling
DE: 4920 Dendrochronology
DE: 4958 Speleothems
SC: Biogeosciences [B]
MN: 2007 Fall Meeting