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Ocean acidification, mammal respiration, and aerosol formation all depend on chemistry that occurs at air-water interfaces. In new research, scientists from the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have discovered which pathway carbon dioxide (CO2) molecules follow on their way from the atmosphere into water – and it's not the one that they expected.
The oceans absorb roughly 30% of all anthropogenic CO2 emissions. In water, the CO2 forms carbonic acid, changing the marine environment in ways that are harmful to some sea life. In our bodies, air that crosses the wet membranes lining our nasal tracts influences the pH of our blood. But just how the local chemistry changes depends on how the dissolved CO2 separates into two different ions with different charges – doubly charged carbonate and singly charged bicarbonate – near the liquid surface. Berkeley Lab researchers now show an enhanced concentration of carbonate at air-water interfaces, where they expected to find more bicarbonate.
"The carbon cycle of Earth as well as the respiration cycle of mammals explicitly involves the dissolution of CO2 at the water surface and its transformation into bicarbonate and carbonate ions. Understanding reactions at the air–water interface will further illuminate these vitally important processes," said Jin Qian, a researcher who contributed the theoretical part of the work reported in the Journal of the American Chemical Society. Qian is a staff scientist in the Chemical Sciences Division at Berkeley Lab.