E-AIM Tutorial

Lesson 1: Properties of Single Salt Solutions


Atmospheric particles contain electrolytes, for example the salts NH4NO3 and NaCl and acids such as H2SO4 and HNO3, which are soluble in water. Their presence can lead to some or all of the particle existing as an aqueous solution, depending on the atmospheric conditions.

The amount of water in an aerosol particle depends on the nature of the electrolytes, the quantities present, and on the ambient relative humidity and temperature. The aerosol water determines the concentrations of the dissolved electrolytes and consequently the ion activities. These in turn control equilibria of volatile species such as NH3 and HNO3 with the surrounding atmosphere, and the formation of solid salts within the aerosol particle.

This lesson will help you to understand the relationship between the water content of a particle and relative humidity, and the influence on ion activities, for systems containing a single electrolyte at constant temperature. In part (a) of the lesson the output of the model, and the meaning of the various quantities presented, will be explained.


Before starting, ensure that this browser window occupies only the left half of your screen. You should leave enough space for another browser window where you can enter data into E-AIM and read the results. If your screen is too small for two windows, print out this tutorial and use this window to enter data and read E-AIM's results. In these lessons we assume that you will have two browser windows open.

Select this link to open a second browser window containing the data input page for "simple" calculations using Model III (http://www.aim.env.uea.ac.uk/aim/model3/model3a.php). Arrange the windows on your screen so that both are visible and the left window contains this text.

The Lesson

This consists of the four sets of calculations described in the links below, which should be done in the order listed.

   a.  Aqueous solutions at a fixed relative humidity
   b.  Increasing the amounts of electrolytes
   c.  Reducing the relative humidity
   d.  Properties over a range of relative humidities


You have completed Lesson 1, and learned:

Now proceed to Lesson 2, which examines how solid phases form in aqueous aerosols at different relative humidities.