The role of nitric acid in atmospheric new particle formation

Abstract

Nitric acid, an air pollutant with strong acidity and oxidizability, can be found in considerable quantities in the gas and aerosol phase. Understanding the role of nitric acid in atmospheric new particle formation is essential to study the complicated nucleation mechanism. Using density functional theory combined with the Atmospheric Clusters Dynamic Code (ACDC), the role of nitric acid in the formation of new particles has been investigated under different atmospheric conditions (different precursor concentrations and temperatures). The results show that nitric acid can form clusters with sulfuric acid and ammonia by hydrogen bond or even proton-transfer interactions. The concentrations of clusters involving nitric acid can be comparable with those of sulfuric acid-ammonia-based clusters, considering the thermodynamic stability combined with the realistic atmospheric concentrations of precursors. Within the atmospheric concentration range, nitric acid can enhance the formation rates of sulfuric acid-ammonia clusters, especially at low temperature, low sulfuric acid concentration and high ammonia concentration. In addition, the new particle formation mechanism indicates that nitric acid can contribute to the cluster formation and the role of nitric acid in the cluster formation pathway is as a "bridge" connecting the smaller and larger clusters.

Self-Catalytic Reaction of SO3 and NH3 To Produce Sulfamic Acid and Its Implication to Atmospheric Particle Formation

“…SFA molecule shows an ability to directly participate in the cluster formation, suggesting that SFA can be a “participator” in facilitating NPF. Contrary to other common acid species as reported in our recent works, ,, such organic acids, e.g., lactic acid and glyoxylic acid, and inorganic acids, e.g., nitric acid, can only be indirectly involved in the growth pathway, acting as a “transporter” (which initially participates and eventually evaporates). Note that, like SFA, another two species with sulfonic group, namely, methanesulfonic acid (MSA) and hydroxymethanesulfonic acid (HMSA), are also identified to directly participate in the cluster formation.…”

Rapid growth of new atmospheric particles by nitric acid and ammonia condensation

“…3c are too slow to compete in urban new-particle formation, this mechanism may provide an important source of new particles in the relatively clean and cold upper free troposphere, where ammonia can be convected from the continental boundary layer 29 and abundant nitric acid is produced by electrical storms 4 . Theoretical studies have also suggested that nitric acid may serve as a chaperone to facilitate sulfuric-acid–ammonia nucleation 30 . Larger (60–1,000 nm) particles consisting largely of ammonium nitrate, along with more than 1 ppbv of ammonia, have been observed by satellite in the upper troposphere during the Asian monsoon anticyclone 4 , and abundant 3–7-nm particles have been observed in situ in the tropical convective region at low temperature and condensation sink 5 .…”

Particle formation and surface processes on atmospheric aerosols: A review of applied quantum chemical calculations

“…[ 78 ] The artificial bee colony (ABC) algorithm has recently been employed extensively to study atmospherically relevant clusters. [ 79–84 ] Recently, a new systematic method of configurational sampling based on the Fibonacci sphere has been applied to atmospheric molecular clusters. [ 85,86 ] Once all the low‐energy isomers are identified by one of these configurational sampling methods, [ 87 ] the main parameter of interest to be computed using quantum chemistry is the equilibrium constant of formation under atmospherically relevant conditions dictated by the temperature, pressure, and RH.…”