researchers are trying to unravel the mysteries of water with “unique characteristics in the world”

This CNRS researcher, who has worked in the geochemistry section for more than 20 years, took a Paris-Tarbes train on Thursday and then the car for an hour to get to the small chapel. The trip is worth the effort: there flows sulfurized spring water with exceptional characteristics, which according to…

This CNRS researcher, who has worked in the geochemistry section for more than 20 years, took a Paris-Tarbes train on Thursday and then the car for an hour to get to the small chapel. The trip is worth the effort: there flows sulphurized spring water with exceptional characteristics, which, according to our researcher, presents “chemical anomalies unique in the world”.

Now converted into a spa house, the place itself has a unique history: it is the last active survivor of the small spa establishments that dotted the foothills of the Pyrenees centuries ago.

The water in the chapel presents unique chemical “anomalies” in the world

The origin of the emergency baths dates back, according to legend, to the Gallo-Roman era. Cut stones found near the springs show that the waters were already used 2500 years BC.

Later, in 1750, Théophile de Bordeu, a native of the Vallée d’Ossau, already speaks in his letters of a small, fairly rudimentary establishment, but with miraculous springs where the inhabitants of the neighborhood came to treat all sorts of ailments. However, for quite a long time, this water with unknown characteristics and a particular smell gave the site the name of “witch” water. “It smells a bit like a rotten egg, what a stink! comments Peter.

The house of the baths was rebuilt in 1787, then enlarged in 1866, but no one has ever managed to discover the secret of its water.

Unexplained abnormalities

At the entrance to the spa house, you must take off your shoes and not make noise to respect the place of meditation and rest. Inside, people come to recharge their batteries in baths with revitalizing properties.

At the bottom of the thermal house, a chapel, about 10 m² welcomes the visitor, illuminated by a pretty light filtered by a stained glass window. Above all, it shelters the spring water which interests our researcher so much. A small hole, about thirty centimeters on a side, contains the water that pours into it. Who pours into it from where? “We don’t even know,” smiles Pierre Cartigny. “We know almost nothing about this source, it’s crazy. As the baths have existed for over two centuries, there is no written record of their origin. »

The water has sulfur isotope anomalies. The source is “abnormal” because the hydrogen sulphide it contains (denoted H2S, which smells of rotten eggs) is enriched in sulfur 33 and the sulphates (denoted SO4) are depleted in sulfur 33.

The mechanism that produces these abnormalities is not understood. It could be of microbial origin (or not) and is all the more troubling since all the other sources in the region (which have all been resampled and reanalyzed) show no anomalies.

Almost nothing is known about this source

Pierre Cartigny remembers 2018, when Guillaume Barré, then a young researcher at Total, had to resample many sources to verify their values. He goes to this chapel in Béarn and realizes a sulfur isotope anomaly in this water. Upon Guillaume’s return to the laboratory, Pierre remembers his reaction: “I told him that he must have made a mistake in his samples, because these anomalies are extremely rare,” he smiles today. But subsequent samples tracked the same anomalies, and researchers began to pay attention.

After the period of health crisis, research is therefore carried out within the CNRS. Every month, Pierre and his Pau colleague Anthony Ranchou-Peyruse go to the chapel and fill several liters of this unique water. Once back in Paris, she will undergo many experiments: “First, we filter it to obtain only the reagent and the powder thus created. Several other transformations are performed until we obtain a molecule that we know how to compare with other molecules and from which we can extract values. »