A sulfuric acid nucleation potential model for the atmosphere

Abstract

Abstract. Observations over the last decade have demonstrated that the atmosphere contains potentially hundreds of compounds that can react with sulfuric acid to nucleate stable aerosol particles. Consequently, modeling atmospheric nucleation requires detailed knowledge of nucleation reaction kinetics and spatially and temporally resolved measurements of numerous precursor compounds. This study introduces the Nucleation Potential Model (NPM), a novel nucleation model that dramatically simplifies the diverse reactions between sulfuric acid and any combination of precursor gases. The NPM predicts 1 nm nucleation rates from only two measurable gas concentrations, regardless of whether all precursor gases are known. The NPM describes sulfuric acid nucleating with a parameterized base compound at an effective base concentration, [Beff]. [Beff] captures the ability of a compound or mixture to form stable clusters with sulfuric acid and is estimated from measured 1 nm particle concentrations. The NPM is applied to experimental and field observations of sulfuric acid nucleation to demonstrate how [Beff] varies for different stabilizing compounds, mixtures, and sampling locations. Analysis of previous field observations shows distinct differences in [Beff] between locations that follow the emission sources and stabilizing compound concentrations for that region. Overall, the NPM allows researchers to easily model nucleation across diverse environments and estimate the concentration of non-sulfuric acid precursors using a condensation particle counter.

Sulfuric Acid Nucleation Potential Model Applied to Complex Reacting Systems in the Atmosphere

“…The nucleation time and mixing times were estimated using an Ansys computational fluid dynamic simulation of the centerline velocity of the laminar flow within the reactor. The nucleation reaction time was optimized to minimize particle concentrations >2 nm, as detailed in Johnson and Jen (2022).…”

“…The Nucleation Potential Model (NPM) was developed to describe how multi‐component chemical systems influence SA nucleation rates (Johnson & Jen, 2022). NPM is a semi‐empirical model that simplifies the numerous and often unknown nucleation reactions into a single acid‐base reaction pathway for forming a 1 nm particle (Johnson & Jen, 2022).…”

“…The Nucleation Potential Model (NPM) was developed to describe how multi‐component chemical systems influence SA nucleation rates (Johnson & Jen, 2022). NPM is a semi‐empirical model that simplifies the numerous and often unknown nucleation reactions into a single acid‐base reaction pathway for forming a 1 nm particle (Johnson & Jen, 2022). The main parameter of the model is the effective base concentration ([ B eff ]) which describes the concentration and potency of the nucleation precursors in a sample.…”

“…The main parameter of the model is the effective base concentration ([ B eff ]) which describes the concentration and potency of the nucleation precursors in a sample. NPM was recently applied in Johnson and Jen (2022) to describe the [ B eff ] of amines and ammonia along with mixtures of these compounds with higher [ B eff ] values enhancing SA nucleation rates more. [ B eff ] is determined with the concentration of 1‐nm particles formed after reacting a known amount of SA with sampled gas for a specific nucleation time.…”

Reducing chemical complexity in representation of new-particle formation: evaluation of simplification approaches

“…Multi-compound systems can also be reduced to quasi-unary systems by implicit treatment of compounds. [24][25][26][27][28] This corresponds to assuming that one or more compounds do not need to be explicitly included, but only affect the cluster properties, most importantly the cluster evaporation rates which generally strongly depend on the molecular composition. 29,30 This corresponds to representing, for example, all cluster compositions A 3 B X that consist of three molecules of compound A and any number of molecules of compound B, as a single cluster A 3 with effective properties that are affected by the presence of B.…”