Magnetic resonance imaging also sheds light on history without destroying fragile finds – ancient Roman harbour wooden structures analysed at the University of Oulu, Finland

Rare 3rd Century CE wooden structures found in Naples, Italy but made during the Roman Empire, have been investigated using nucleal magnetic resonance (NMR) techniques. These methods, commonly known in hospital magnetic resonance imaging (MRI) scans for producing detailed images of the human body, have been shown to be valuable in revealing secrets in archaeological discoveries.

The samples are from the wooden poles of an ancient pier forming part of a Roman harbour which were discovered during excavations for a metro line in Naples. The discoveries required the route of the metro line to be diverted and now runs beneath the archaeological site.

“It is rare that ancient organic wooden structures are found at all, as they usually degrade over time. The exceptional discovery was made possible by the [humidity of the] aquifer that has preserved the pier structures,” says Dr. Otto Mankinen, a post-doctoral researcher at the University of Oulu.

The NMR spectroscopy used does not damage the target material. Its non-invasive nature proves particularly important when examining archaeologically valuable samples or, for example, paintings prior to restoration. Other methods, such as X-ray or light microscopy, damage samples and they can sometimes require samples to be sliced. This would have proved a destructive and challenging process to deal with the fragile and spongy underwater remains of the wood. If lifted into the air, samples can decay.

In the study, the wood samples remained in similar conditions to those they had spent the intervening centuries. It aimed to find out how wood behaves and survives in water and to reconstruct the changes caused by decay. And to make a comprehensive analysis of the structure and changes in archaeological wood remains.

The study is one of the first to combine four different NMR techniques: relaxometry, micro-imaging, diffusometry and cryoporometry. Archaeological samples of spruce, chestnut and maple were compared with fresh wood material from the same species.

"The valuable samples were analysed at the University of Oulu, as one of our long-standing research topics has been the analysis of wood materials. The best way forward would be to take NMR equipment on-site to historic finds, which are often too fragile to move," said Mankinen. The new findings will also contribute to the development of mobile NMR instruments.

In recent years, NMR techniques have become faster and more sensitive, and the trend is also towards smaller and smaller instruments. Mobile NMR instruments are also less expensive.

There are high expectations and promising results for practical applications of NMR spectroscopy in several fields, such as environmental and atmospheric monitoring, battery materials, eco concrete, mine water and catalysts, and biochemistry, as shown in a doctoral thesis at the University of Oulu on December 2024.

The study ‘Comprehensive characterization of waterlogged archaeological wood by NMR relaxometry, diffusometry, micro-imaging and cryoporometry’ was carried out in collaboration with researchers from Sapienza University of Rome and published in October 2024 in Physical Chemistry Chemical Physics.

To read more visit: 10.1039/D4CP02697G 

-- EurekAlert.org