Title: Sulphur variations in annually layered stalagmites using benchtop micro-XRF

Abstract

Variation of sulphur in annually laminated stalagmites can be used to infer the impact of past volcanic activities, anthropogenic pollution, and climate change due to increased bushfire activity. The synchrotron radiation micro-X-Ray fluorescence (SR-XRF) microprobe is a powerful tool to analyse and image sulphur recorded in stalagmites with micrometre resolution. However, access to SR-XRF beamlines can be limited, so researchers must select the most promising stalagmites for imaging. Benchtop micro-XRF is an effective tool for trace elemental analysis of speleothem samples and is a candidate for routine laboratory measurement of sulphur along stalagmite laminae and screening for SR-XRF. Here, this study describes a protocol using matrix-matched standards to measure annual variations of sulphur at trace to percent level along the laminae of two Western Australian stalagmites, one of which already having been analysed using SR-XRF. Parameters that affected quantitation include X-ray tube voltage and current, spot size of the X-ray beam and stalagmite surface roughness and porosity. The use of a 20 μm X-ray spot size provides sub-annual spatial resolution that can be completed in an overnight scan. The features in a 1000 point micro-XRF analysis of sulphur along a 20 mm transect show good consistency with SR-XRF microprobe data.more » Micro-XRF mapping was also performed to produce chemical images on the stalagmite and compared with Raman and X-ray diffraction (XRD) to confirm that the stalagmite is exclusively calcite, with no aragonite, and that the source of sulphur in the samples was gypsum and anhydrite. Regions of very high sulphur in the micro-XRF maps were found to be artefacts due to diffraction of the incident beam but these could be efficiently removed by using a multiple point statistics approach to produce a clean image suitable for analysis of the laminae. This work shows the potential of micro-XRF for routine analysis of sulphur in stalagmites, and to streamline sample characterisation before SR-XRF imaging.« less

Authors:

Wang, Huixin ^[1]; Treble, Pauline ^[2]; Baker, Andy ^[2]; Rich, Anne M. ^[1]; Bhattacharyya, Saroj ^[1]; Oriani, Fabio ^[3]; Akter, Rabeya ^[1]; Chinu, Khorshed ^[1]; Wainwright, Irene ^[1]; Marjo, Christopher E. ^[1]

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+ Show Author Affiliations

1. Univ. of New South Wales, Sydney, NSW (Australia)
2. Univ. of New South Wales, Sydney, NSW (Australia); Australian Nuclear Science and Technology Organisation (Australia)
3. Université de Lausanne (Switzerland)

Publication Date:

Mon Jan 17 00:00:00 EST 2022

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); USDOE

OSTI Identifier:

1981747

Alternate Identifier(s):

OSTI ID: 1868596

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Spectrochimica Acta. Part B, Atomic Spectroscopy

Additional Journal Information:

Journal Volume: 189; Journal Issue: C; Journal ID: ISSN 0584-8547

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Stalagmite; Synchrotron; micro-XRF; Sulphur; Raman; Multipoint statistics