High levels of ammonia do not raise fine particle pH sufficiently to yield nitrogen oxide-dominated sulfate production.

ABSTRACT: High levels of ammonia (NH₃) have been suggested to elevate ambient particle pH levels to near neutral acidity (pH = 7), a condition that promotes rapid SO₂ oxidation by NO₂ to form aerosol sulfate concentration consistent with "London fog" levels. This postulation is tested using aerosol data from representative sites around the world to conduct a thorough thermodynamic analysis of aerosol pH and its sensitivity to NH₃ levels. We find that particle pH, regardless of ammonia levels, is always acidic even for the unusually high NH₃ levels found in Beijing (pH = 4.5) and Xi'an (pH = 5), locations where sulfate production from NO _x is proposed. Therefore, major sulfate oxidation through a NO₂-mediated pathway is not

SUBMITTER: Guo H 

PROVIDER: S-EPMC5608889 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature