Scientists had long assumed that the contamination process occurred deep underground, in buried sediments that release arsenic into aquifers 100 to 130 feet below the surface. But Fendorf and his colleagues had data suggesting otherwise. They suspected that the arsenic actually dissolved at a much higher depth, very close to the surface. "As the water starts to move down into the soil, it picks up arsenic. That was our hypothesis," he said. "We needed to follow the chemistry of the surface water as it moved down into the groundwater."
Fendorf and his colleagues began their fieldwork in the Brahmaputra River basin of Bangladesh. However, creating a hydrology model was a challenge, because the landscape was dotted with irrigation wells that alter the natural path of water. "When you draw out how the water might flow, it looks like spaghetti," Fendorf explained. "Before we even started we said there is no way this is going to be possible."
The researchers needed a less-developed site that was chemically, biologically and geologically similar to Bangladesh. The Mekong River in Cambodia offered a perfect alternative. Its headwaters are only 100 miles away from those of the Brahmaputra River. "All the chemistry up in the Himalayas is similar," Fendorf added. "The transport down the big river system is very similar as well."
More importantly, the Cambodia site was mostly undeveloped. "Cambodia had been under a 35-year civil war that had really repressed its development, so it was in essence Bangladesh 40 or 50 years ago," he said. "In some ways it would actually be setting the clock back and getting a snapshot back in time. By virtue of having this more simplistic system, w
|Contact: Mark Shwartz|