Source: International Atomic Energy Agency – IAEA
“We determined that a 300-meter wide strip of the ground underneath the settlement contains contaminated or potentially contaminated groundwater, while the affluent from the garbage disposal site does not reach the rest of the water under ground in the area,” said Joël Rajaobelison, an isotope hydrologist and Director General of the National Institute of Nuclear Science and Technology (INSTN Madagascar), which has received both equipment and training for its staff from the IAEA, through its technical cooperation programme, to use isotopic techniques for water analysis. “It is therefore safe to use.”
This is important for the villagers not only in the short term but for the coming years: they have petitioned the government to get electricity and running water, and while the construction of electricity poles has begun, there are no immediate plans for piped water reaching the village, Ranorosa said.
While the concentration of isotopes of hydrogen and oxygen – the two elements that make up water – in any water is extremely low, surface water tends to be relatively richer in isotopes 2H – known also as deuterium – and 18O. The sensitive equipment that Rajaobelison’s team uses, and which was donated by the IAEA through its technical cooperation programme, is able to detect the difference and therefore any infiltration of surface water. “If it contains surface water, the groundwater may easily get polluted from the affluent even if it is clean now,” he explained.
Deuterium and 18O are stable isotopes, the kind that do not decay and emit radiation, so they cannot be used to trace the direction and speed of water flow – crucial information in order to be able to identify potentially polluted areas. Enter 3H – known as tritium – which is even rarer and was mostly introduced into the atmosphere as a harmless byproduct of nuclear weapons tests in the 1950s and 60s. Through rain it entered surface water and the water cycle. When found in groundwater, it indicates that the reservoir has been recharged in the last 60 years. The small amounts of radiation tritium molecules emit when decaying is used to trace the direction and speed of water. “Therefore we can tell whether any body of water is coming from the landfill site or flowing towards it,” Rajaobelison said.
When last year his office was alerted to the problem of Ambaniala by a private citizen, who heard about the use of isotopic techniques through a national outreach campaign, his staff knew right away that INSTN can help. “For us it is a simple, routine analysis performed over a number of weeks, Rajaobelison said. “For them it is a life saver.”