Research Spotlights

By Georgia Barrington-Smith & Dr Rebecca Duncan

Anthropogenic-driven climate change has extended the duration of Australia’s annual fire seasons, wreaking havoc on agricultural crops, wildlife, and homes. The 2019-2020 bushfires, which scorched over seventeen million hectares and claimed the lives of over one billion animals, provide a stark example of this growing crisis.

Satellite observations can offer insights into past fire regimes, but such records are not extensive enough to capture the entire range of natural variability, or the feedback between climate, landcover, and human activities. Given that climate models forecast even more intense bushfire seasons in the future, it is critical that research continues to analyse historical data to track these changes. UNSW researcher Dr. Micheline Campbell, in collaboration with ANSTO, has examined the history of Australian bushfires etched in cave deposits (speleothems) to help strengthen our fire management strategies in the future.

The hidden history buried in speleothem caves

Speleothem caves contain stalagmites and stalactites – mineral formations created by groundwater that drips onto the cave floor. These mineral formations can be isotopically dated to determine past climatic conditions, including past bushfires.

Over thousands of years, as bushfires burned above, ash deposited over caves were embedded into speleothems by rainwater, preserving trace element layers of the ash. This process creates ‘paleofire signals’ that act as a chronological record of the environment above the cave, capturing yearly variations over millennia. Research by Dr. Micheline Campbell and her collaborators aims to reconstruct not just the timing, but also the severity of ancient fires by analysing these trace elements preserved in the speleothem archives.

Micheline’s historical hunt for fire information

Micheline and her colleagues began by collecting ash samples from recent bushfires in south-west and south-east Australia. At ANSTO’s Environment Research & Technology (ERT) laboratory, Micheline then performed uranium-series dating techniques on these samples to count their annual growth bands. By analysing this data, she showed that variations in ash metal concentrations were related to the burn severity of the associated bushfires.

Next, Micheline set out to determine whether the severity of burns indicated by ash data was similarly recorded in speleothems. To do this, she collected ‘mini cores’ from the actively-growing tips of stalagmites across different caves in Yanchep National Park, Western Australia – an area that has experienced a variety of bushfires to varying degrees.

Using the X-ray fluorescence microscopy beamline at ANSTO’s Australian Synchrotron, and laser ablation inductively-coupled plasma mass spectrometry at ANSTO’s ERT lab, the team created elemental maps of the samples. Their preliminary results revealed distinctive metal patterns derived from the ash following known fires.

By examining the ash composition and comparing it to stalagmites from areas with recorded fire events, Micheline and her collaborators discovered that the speleothems from Yanchep National Park in south-western Western Australia are likely to offer the sought-after high-resolution records of fire severity and frequency from our deep past.

Historical insights guiding future decisions

Micheline’s research underscores the importance of analysing historical records to enhance our understanding of future environmental changes. The paleo-information archived in speleothem caves can provide significant insights for improving land management strategies, thereby enabling more informed decision-making in response to climate change.

This work is part of an Australian Research Council Discovery Project led by Prof. Andy Baker (UNSW), Dr. Pauline Treble (ANSTO), and Dr. Liza McDonough (ANSTO). It builds on previous studies conducted by ANSTO Environmental Scientist Dr. Liza McDonough, who identified the possibility of reconstructing fire events from stalagmites.

AINSE are proud to spotlight Micheline for her fantastic work!

If you, just like Micheline, are keen to discover the answers to some of Australia’s toughest environmental challenges, visit ainse.edu.au/scholarships to see how AINSE can support you.

To read more research spotlights visit ainse.edu.au/research-spotlights. Additionally, keep an eye out for the second article in our April Awareness issue, where we will showcase the work of Sarah Cooley, an AINSE PGRA scholar, who is using historical records of fire-sensitive Pencil Pine to study the bushfire resilience of Australia.

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By Georgia Barrington-Smith & Dr Rebecca Duncan

For decades, conventional X-rays have been invaluable in clinical settings, enabling doctors and radiographers to gain critical insights into patients’ health. While traditional X-rays are still widely used, they are limited in the depth of information they can provide. New, advanced multimodal techniques, like phase-shift and dark-field imaging, can offer more detailed images, revealing not only bones and metal implants but also microstructures and surrounding soft tissue.

Unlike conventional X-ray imaging, which focuses on the absorption of X-rays by the sample (attenuation), phase-shift imaging captures changes in the phase of X-rays as they pass through the sample. In addition, dark-field imaging highlights small structures such as tiny pores, cracks, or granular textures, providing detailed information beyond the spatial resolution of traditional X-rays.

Enhancing X-ray imaging efficiency with multimodal techniques

Research into multimodal techniques has introduced one promising method: Speckle-Based X-ray Imaging (SBXI). With a simple experimental setup and ability to produce high-quality images with minimal data, SBXI uses a spatially-varied medium (such as sandpaper or textured materials) placed between the X-ray source and detector. This creates speckles—tiny variations in the intensity of the X-rays as they pass through the sample. These speckles act as markers, helping to track the X-ray wavefronts. By analysing how the speckles change as they pass through the sample, additional structural information can be recovered.

Although SBXI shows great potential, there are significant challenges hindering its development, such as the longer time required to construct high-quality images. Therefore, fast, efficient computer-based algorithms are crucial not only for reducing computational time, but also for minimising the radiation exposure to the patient during image reconstruction.

Samantha’s steps towards speckle-based X-rays

Samantha Alloo, an AINSE PGRA scholar, and her collaborators at ANSTO and the University of Canterbury have developed a fast, computationally efficient algorithm capable of reconstructing multimodal signals in just a few seconds. This new algorithm, called Multimodal Intrinsic Speckle-Tracking (MIST), provides on-demand multimodal imaging with low radiation exposure to the patient, or other delicate samples.

MIST uses the principle of energy conservation at small scales to track speckles and generate detailed images in Speckle-Based X-ray Imaging. The dark-field images it produces are especially useful when combined with other traditional X-ray imaging methods, such as Small-Angle X-ray Scattering (SAXS), as they can reveal information about sample structures beyond the limits of the imaging system’s spatial resolution. This capability has already proven valuable in applications including clinical mammography, biosecurity, and engineering crack detection.

Future directions for Samantha’s algorithm

Samantha and her team aim to further develop MIST to create a user-friendly SBXI setup at the MicroCT beamline at ANSTO’s Australian Synchrotron. This setup is designed to retrieve high-quality data comparable to, or even surpassing, well-established imaging techniques. The goal is to make these algorithms computationally efficient and general enough to be applied in a wide range of real-time synchrotron and laboratory experiments.

Samantha hopes to extend the MIST algorithm to work with materials whose properties vary depending on the direction that X-rays travel through the material. This will allow the reconstructed dark-field signal to reveal information about the sample’s microstructure orientation, making MIST suitable for a broader range of samples. This expanded approach will contribute to the overall goal of creating a more robust and user-friendly technique for clinical applications.

Finally, while utilising the MIST algorithm to conduct SBXI experiments, Samantha also hopes to develop a dark-field tensor tomography protocol. This protocol promises to deliver more detailed information about a sample’s internal structure by using SBXI techniques to capture its orientation in three-dimensional space.

AINSE are proud to spotlight Samantha Alloo for her groundbreaking work!

To explore more incredible research by our AINSE scholars, visit ainse.edu.au/research-spotlight.

We’re hanging up our stethoscopes and turning our attention to Bushfire Awareness in April, where we’ll spotlight two AINSE scholars doing crucial research on Australia’s bushfires and explore how science is driving better outcomes for our community.

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