Text S1. Specific Application of Thermodynamic State Equations
in a Reduced Nitrogen Compound (RNC)-Sulfuric Acid-Nitric Acid chemical
system
The Extended-Aerosol Inorganics Model (E-AIM) considers the partitions
of a particular chemical in four phases: gas (g), solid (s, including
its salts), aqueous solution (aq) and hydrophobic organic solution (org)
at any given relative humidity and temperature in a fixed total volume
of 1 m3 and at a fixed total pressure of 101,325 Pa.
The E-AIM model (http://www.aim.env.uea.ac.uk/aim/aim.php) allows the
users to specify the initial concentration of the chemical (as moles in
1 m3), as well as instructions regarding the
properties and activity (discussed in details in following sections) of
the chemical.
All possible states for water (g, aq and s) are considered by the E-AIM.
However, in this study, low temperatures at which the water may start to
freeze were avoided. The autoprotolysis of water and both hydrolysis
equilibria of the inorganic diacid H2SO4are also considered to include H+,
HSO4− and OH−concentrations in the calculations. The protonation of ammonia and the
formation of ammonium nitrate and sulfate solids are considered in our
simulations to represent the partition of ammonia in aqueous solution
and solid phases as accurately as possible. Since
NH4+,
SO42− and
NO3− are the primarily inorganic ions
of consideration, E-AIM Model II was used throughout our study.
Thermodynamic data on ammonia and its nitrate and sulfate salts have
been extensively studied and their thermodynamic properties and
constants are relatively well established.1 Therefore,
default inputs (including the methods to estimate activities) in the
existing E-AIM Model II on ammonia, sulfuric acid and nitric acid are
used without further modification. Wang et al.2identified that ammonia and nitric acid in the ammonia-sulfuric
acid-nitric acid ternary system could only condense at or below 278 K,
but above 263 K, suggesting that our simulation results on the
ammonia-sulfuric acid-nitric acid ternary system should have an
uncertainty within the range of −3.8% to +1.7%.
In this study, for example, the following series of state equations are
possible for ethanolamine (MEA, with its conjugated acid labeled as
MEAH+):
\(\text{MEA\ }\left(g\right)\rightleftharpoons MEA\left(\text{aq}\right)\)Eq. S1
\(\text{MEA\ }\left(\text{aq}\right)+\ H^{+}(aq)\rightleftharpoons\text{MEAH}^{+}\left(\text{aq}\right)\)Eq. S2
\(\text{MEAH}^{+}\left(\text{aq}\right)+\text{NO}_{3}^{-}(aq)\rightleftharpoons
MEA\bullet HNO_{3}\left(s\right)\)Eq. S3
\(MEA\bullet HNO_{3}\left(s\right)\rightleftharpoons MEA\left(g\right)+\ HNO_{3}\left(g\right)\)Eq. S4
\(2\text{MEAH}^{+}\left(\text{aq}\right)+\text{SO}_{4}^{2-}(aq)\rightleftharpoons 2MEA\bullet H_{2}SO_{4}\left(s\right)\)Eq. S5
\(2MEA\bullet H_{2}SO_{4}\left(s\right)\rightleftharpoons MEA\left(g\right)+\ H_{2}SO_{4}\left(g\right)\)Eq. S6
Each of the equation above involves an equilibrium constant Kthat is temperature dependent and may have been determined
experimentally or can be derived using other thermodynamic properties of
MEA.