As the population and water needs of Hanoi mushroom, the capital city of Vietnam is slowly drawing poisonous arsenic into the aquifer that supplies its drinking water, say researchers from the U.S. and Vietnam. Water contaminated with arsenic has moved more than a mile
closer to the aquifer over the last 40 to 60 years, the researchers report in Nature, due to the city’s increasing water demand; municipal pumping in Hanoi doubled between 2000 and 2010. The good news, says lead researcher Alexander van Geen of Columbia University’s Lamont-Doherty Earth Observatory, is the contaminated groundwater “is not moving as fast as we had feared it might.” This will give Hanoi officials time, perhaps decades, to determine how to best deal with the problem. The study also determined why arsenic is leaching into the groundwater: As water containing arsenic mixes with high levels of organic carbon from the Red River and other surrounding aquifers, the chemistry changes and arsenic dissolves in the water.