Synchrotron radiation applications to past volcanism archived in speleothems: An overview Silvia Frisia a, ⁎, Andrea Borsato b , Jean Susini c a School of Environmental and Life Sciences, The University of Newcastle, Callaghan, New South Wales, Australia b Museo Tridentino di Scienze Naturali, via Calepina 14, 38100 Trento, Italy c European Synchrotron Radiation Facility, F-38043 Grenoble Cedex, France abstract article info Article history: Received 11 January 2007 Accepted 14 November 2007 Available online 28 November 2007 Keywords: synchrotron radiation speleothems sulphate past volcanism Precise dating and correlation of past key volcanic eruptions over a wide geographic area in archives of past climate variability is necessary to support a direct causality between volcanism and climate changes. Research has mostly focused on ice cores and varved sediments, which capture a record of volcanic eruptions in geochemistry and the presence of tephra and criptotephra. Precisely dated cave carbonate deposits, collectively known as speleothems are other valuable palaeoclimate archives, and encode information on past volcanism in their sulphate concentration variability. Due to the physical characteristic of speleothems, detection of sulphate concentration variability requires techniques capable of high spatial resolution, very low limit of detection (ppm to ppb) and low background noise. Synchrotron radiation-based (SR) micro X-ray fluorescence (μXRF) and X-ray absorption near-edge spectrometry prove to be one of the most effective techniques to detect short-lived pulses of sulphate concentration increase, which may be interpreted as being related to atmospheric load due to volcanic eruptions. Here, we provide an overview of existing work as well as a novel interpretation of a SR μXRF-based sulphate series in an annually laminated stalagmite with robust chronology. Sulphate concentration peaks in the years 1815–1816, 1844 and 1947, possibly coinciding with Tambora, Krakatau, and Hekla eruptions. It is concluded that sulphate concentration in speleothems expand the potential to correlate volcanic eruption events at a global scale. © 2007 Elsevier B.V. All rights reserved. 1. Introduction Sulphur dioxide ejected during explosive volcanic activity changes the loading level of stratospheric sulphate aerosol, back-scattering the incoming solar radiation and leading to a lowering of ground temperatures for a few years following the eruption (Zielinski, 2000; Watanabe et al., 2004). Significant short-term perturbations in climate have been ascribed to the effects of volcanic eruptions on the Earth's atmosphere (Briffa et al., 1998; Chenoweth, 2001; Bradley et al., 2003). Controversy, however, surrounds the impacts on climate and the environment of powerful volcanic eruptions because of the difficulty of precisely correlating key volcanic events between ice cores, marine and continental archives. Our knowledge of the timing and impacts of Pleistocene and Holocene major eruptions has been based, until recently, largely on high-latitude ice-core acidity peaks (Zielinski, 2000). Ice-core records, however, can be affected by time delay in the arrival of volcanic aerosols compared to the mid-latitudes. This was the case, for example, for Pinatubo sulphate aerosols (Watanabe et al., 2004). Dating of volcanic eruptions detected through acidity peaks in ice cores had also been problematic, with the exception of the last few hundred years (Southon, 2002). Since the discovery and identification of tephra and criptotephra in NGRIP ice-cores, precise absolute timescales have been obtained (Davies et al., 2007a). There is urgent need for similar precisely dated archives at mid and low latitudes to perform hemisphere to global scale correlations. Ice cores from mid-latitude are relatively rare, being restricted to small ice caps at elevations well above 2000 m a.s.l. (above sea level). In these high-elevation sites, the downward flux of aerosols results in an increasing decay trend compared to the mid- and low-altitude regions (Watanabe et al., 2004). The regional environmental and climate impacts of volcanism below the aerosol-laden, mid-altitude boundary layers at mid-latitude sites is, so far, poorly known. At mid- and low-latitude other archives are needed to complement high latitude ice records and provide new insights on volcanic sources and volcanism effects on the climate system. Tree rings offer precise and accurate dates for key volcanic events and can record their global climatic influence (Briffa et al., 1998). However, the assertion that growth anomalies are a well-dated proxy of climatically effective volcanism has been disputed due to the lack of a direct causal connection (Pearson et al., 2005). Dendrochemistry detects volcani- cally induced changes in environmental chemistry and can be applied Journal of Volcanology and Geothermal Research 177 (2008) 96–100 ⁎ Corresponding author. E-mail address: silvia.frisia@newcastle.edu.au (S. Frisia). 0377-0273/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jvolgeores.2007.11.010 Contents lists available at ScienceDirect Journal of Volcanology and Geothermal Research journal homepage: www.elsevier.com/locate/jvolgeores