A Caltech Library Service

Ammonia and nitric acid concentrations in equilibrium with atmospheric aerosols: Experiment vs theory

Hildemann, Lynn M. and Russell, Armistead G. and Cass, Glen R. (1984) Ammonia and nitric acid concentrations in equilibrium with atmospheric aerosols: Experiment vs theory. Atmospheric Environment Part A-General Topics, 18 (9). pp. 1737-1750. ISSN 0960-1686. doi:10.1016/0004-6981(84)90349-4.

PDF - Submitted Version
See Usage Policy.


Use this Persistent URL to link to this item:


The equilibrium between gaseous ammonia, nitric acid, and aerosol nitrate is discussed on the basis of a recent field experiment in southern California. Comparison is drawn between theoretical equilibrium calculations and simultaneous measurements of nitric acid, ammonia, ammonium ion, nitrate ion, sulfate ion, other ionic species, temperature and dewpoint. Particulate and gaseous pollutant concentrations at some inland sampling sites are readily explained if the aerosol is assumed to exist as an external mixture with all particulate nitrate and ammonium available to form pure NH_4NO_3. At other monitoring sites, especially near the coast, aerosol nitrate is found in the presence of NH_3 and HNO_3 concentrations that thermodynamic calculations show are too low to produce pure NH_4NO_3. This can be explained when the amount of aerosol nitrate that can be derived from reaction of nitric acid with sea salt and soil dust is taken into account. A calculation approach that accounts for the presence of mixed sulfate and nitrate salts improves the agreement between predicted and observed pollutant concentrations in the majority of cases studied. Uncertainties in these calculations arise from a number of sources including the thermodynamic quantities, and the effect of these uncertainties on the comparison between theory and experiment is discussed.

Item Type:Article
Related URLs:
URLURL TypeDescription
Additional Information:© 1984 Pergamon Press Ltd. This work was supported by the California Air Resources Board under Agreement No. A2-150-32, and by gifts to the Environmental Quality Laboratory.
Group:Environmental Quality Laboratory
Funding AgencyGrant Number
California Air Resources BoardA2-150-32
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Environmental Quality LaboratoryA-162
Issue or Number:9
Record Number:CaltechAUTHORS:20140923-083351037
Persistent URL:
Official Citation:Lynn M. Hildemann, Armistead G. Russell, Glen R. Cass, Ammonia and nitric acid concentrations in equilibrium with atmospheric aerosols: Experiment vs theory, Atmospheric Environment (1967), Volume 18, Issue 9, 1984, Pages 1737-1750, ISSN 0004-6981, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49921
Deposited On:23 Sep 2014 17:37
Last Modified:10 Nov 2021 18:49

Repository Staff Only: item control page