New Insight into Acid Rain Chemistry

A multidisciplinary team led by Dr. A. J. Colussi, comprising of graduate student Himanshu Mishra, and Professor Michael Hoffmann along with Dr. Robert J. Nielsen and Professor William A. Goddard III from the Materials and Process Simulation Center, has shown that the dissociation of nitric acid on thin layers of water, such as those in contact with air or biological membranes, is dramatically different from the similar process inside water. They have found that the molecules of nitric acid do not dissociate when they collide with water unless its surface contains at least 1 anion per million water. This work explains how minute concentrations of anions might subtly participate in acid rain chemistry, the cycling of nitrogen oxide pollutants on urban haze, and in the charging of protein surfaces that drive enzyme activities. [The PNAS Article]