Ancient Roman aqueducts could reveal information about the climate thousands of years ago.
Mineral deposits that coat the aqueducts are being examined in order to study what the climate was like in the days of the Roman Empire. These layers consist mostly of calcium carbonate, the same material found in eggshells, pearls and the shells of snails. Trapped within this material are clues about the environment at the time the aqueducts were in use.
"What we hope to do is to obtain information about paleoenvironmental conditions during Roman times and see if it's different from nowadays," Cees Passchier from the Johannes Gutenberg University in Germany said.
Rome was known for the construction of aqueducts around its vast territory. This allows modern researchers an opportunity to examine what the climate was like at that time around the Mediterranean, as well as northern Africa.
Limestone cave springs were utilized as water sources for many of the aqueducts. This water was rich in dissolved substances such as calcium carbonate, which leeched from cave walls, and carbon dioxide, trapped in the liquid while it was in the spring. When this water reached the open air aqueduct, the carbon dioxide was released to the air, lowering the acidity of the liquid. This drove carbon carbonate out of the water, forming deposits known as sinter, in a process similar to hard water deposits forming in modern plumbing systems. Around 40 percent of Roman aqueducts are coated in layers of sinter.
Researchers examined the abundance of an isotope called oxygen-18, which contains two more neutrons than its more prevalent cousin, oxygen-16. The additional mass of these extra neutrons causes oxygen-18 to precipitate out of water at a greater rate than the more common variety of atoms. These coatings built up year after year, similar to the growth of tree rings. Layers which formed in winter are darker, containing higher concentrations of oxygen-18 than the lighter regions, which formed during summer months. However, higher temperatures are not the only conditions that helped form the different layers.
"These distinct layers can mean many things, such as a drought period, very wet period, or even human activity like a cleaning process of the subject aqueduct," Gül Sürmelihindi of Johannes Gutenberg University stated in a press release.
By examining a combination of radioactive dating and tree rings, and comparing this data to the known history of the climate, researchers could date calcium carbonate layers in aqueducts with an accuracy of just five years.
By the time the Roman Republic fell and the Empire began over 2,000 years ago, more than a million people were supplied with water from the extensive aqueduct network. By studying the ancient climate, researchers may learn previously-unknown information about the history of one of the greatest civilizations in history.
Photo: Michael E. Lee | Flickr