Air Date: Week of July 8, 2011

The thin blue line between water is surprisingly hard to determine. But knowing how to make that distinction has big implications for environmental chemistry. Living on Earth’s Stephanie McPherson reports. (Photo: Ankakay)

Transcript

GELLERMAN: Coming up: Dethroning the lords of water and other environmental consequences of the war in Afghanistan, but first this note on emerging science from Stephanie McPherson.

[SOUND: WAVES AND SEAGULLS]

Waves rolling through the ocean look completely separate from the salty air above as they crash down and sink back into the depths. But researchers at the University of Southern California have discovered that the boundary between air and water is not so cut and dried.

[SCIENCE NOTE THEME MUSIC]

One quarter of the water molecules sloshing around at the surface are sitting across the border separating the liquid of the ocean from the gas of the atmosphere.

To test this, scientists used extremely distilled water and singled out the thinnest layer of molecules ever examined. They found that one of every four water molecules right at the air-water boundary was not all wet.

Of the two hydrogen atoms in one molecule of H2O, one hovered just over the water line, free of the usual bonds that kept its underwater partner a liquid. If the molecule were a person, said one of the researchers, it would look like a swimmer waving one arm up out of the water for help.

Many of the chemical reactions that happen at the water’s surface help to keep our atmosphere in balance. Probing the nuances of where water meets air gives environmental chemists more precise information to work with when calculating the rates of these reactions.

Next up, the team will check how salt- and particle-saturated bodies of water compare to their pure water results. That's this week's note on emerging science. I'm Stephanie McPherson.

[SCIENCE NOTE THEME]

 

Links

Nature Article: Hydrogen Bonding at the Water Surface Revealed by Isotopic Dilution Spectroscopy

Water’s Surface Not All Wet