Advertisement

If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.

ENJOY UNLIMITED ACCES TO C&EN

Environment

Water Helps Form Ammonium Bisulfate Salt In Air

Atmospheric chemistry: Reaction may be important for aerosol formation leading to weather, climate, and health effects

by Jyllian Kemsley
February 8, 2016 | A version of this story appeared in Volume 94, Issue 6

[+]Enlarge
In a proposed mechanism for atmospheric NH4HSO4 formation, one H2O (red) breaks apart to give OH to SO3 and H+ to another H2O (green). The H2O that receives the H+ transfers one of its original H+ ions to NH3 to form NH4+.
Drawing of arrangement of ammonia, sulfur trioxide, and three water molecules.
In a proposed mechanism for atmospheric NH4HSO4 formation, one H2O (red) breaks apart to give OH to SO3 and H+ to another H2O (green). The H2O that receives the H+ transfers one of its original H+ ions to NH3 to form NH4+.

Sulfate salts in the atmosphere play a critical role in nucleating and enlarging aerosol particles, which can seed precipitation, reflect or absorb solar radiation, and harm health. But the mechanisms behind the formation of salts such as ammonium sulfate have yet to be fully detailed. Computational work now indicates that ammonium bisulfate can form from the pollutants ammonia and sulfur trioxide, mediated by water (J. Am. Chem. Soc. 2016, DOI: 10.1021/jacs.5b13048). NH3 is emitted by agricultural operations and SO3 by fossil-fuel burning. A team at the University of Nebraska, Lincoln, led by Joseph S. Francisco and Xiao Cheng Zeng found that water molecules from a water trimer or droplet form a looplike network connecting NH3 and SO3 molecules. The network facilitates water-mediated proton transfer in which one water breaks apart, giving OH to SO3 to form HSO4 and an H+ to another water. The water that receives the H+ transfers one of its original H+ ions to NH3 to form NH4+. The reaction has a low barrier and consequently may play a significant role in the formation of aerosol particles.

Article:

This article has been sent to the following recipient:

0 /1 FREE ARTICLES LEFT THIS MONTH Remaining
Chemistry matters. Join us to get the news you need.