Seinfeld_pandis_ch7

Full cloud chemistry system with pH computed from the electroneutrality condition — Seinfeld & Pandis (2006), Ch. 7. The model composes AqueousEquilibria (quadratic charge-balance H⁺ from dissolved CO2, SO2, NH3, HNO3, H2O2, and O3 equilibria) with SulfateFormation (S(IV) oxidation kinetics via O3, H2O2, and Fe/Mn pathways). Unlike CloudChemistryFixedpH, which prescribes H⁺ from an external pH_input, this model self-consistently solves for the cloud-water pH from the trace-gas composition. Migrated from Aerosol.jl@c8c640bb src/cloud_chemistry.jl:73.

Simplified cloud chemistry system with pH as an externally prescribed input parameter — Seinfeld & Pandis (2006), Ch. 7. Instead of computing pH from the electroneutrality condition (as in the full CloudChemistry model), this variant takes pH_input as an input and derives H_plus = C_ref × 10^(-pH_input). This is useful for sensitivity studies that vary pH, for cases where unmeasured ions affect pH, or for quick calculations that bypass the full equilibrium solve. The model composes seven aqueous-equilibrium subsystems (WaterEquilibrium, CO2Equilibria, SO2Equilibria, NH3Equilibria, HNO3Equilibria, H2O2Equilibria, O3Equilibria) and the SulfateFormation oxidation kinetics module (O3, H2O2, and Fe/Mn-synergism pathways). All equilibria use van't Hoff temperature dependence from Table 7.4. Migrated from Aerosol.jl@c8c640bb src/cloud_chemistry.jl:269.

Combined aqueous-phase S(IV)->S(VI) oxidation kinetics — Seinfeld & Pandis (2006), Atmospheric Chemistry and Physics, 2nd ed., Chapter 7, Section 7.5, with the Section 7.4 rate conversions. The model composes five S(IV)-oxidation pathway subsystems — O3 (Eqs. 7.79-7.80), H2O2 (Eq. 7.84), Fe(III)-catalyzed (Eq. 7.92), Mn(II)-catalyzed (Eq. 7.101), and Fe/Mn synergism (Eq. 7.102) — wired to shared cloud-droplet inputs by coupling equations. The total oxidation rate R_total sums the O3, H2O2 and Fe/Mn-synergism rates (the femn_ox subsystem already carries Fe-only and Mn-only terms, so the standalone fe_ox/mn_ox rates are excluded to avoid double-counting). It also reports sulfate production S_VI_production = R_total and three Section 7.4 diagnostics: the rate in ppb/hr (Eq. 7.75) and %/hr (Eq. 7.76) and the SO2 lifetime tau_SO2 (Eq. 7.78). Migrated from Aerosol.jl SulfateFormation as a subsystem-composed model (ESS spec §4.7).

ModelingToolkit implementation of the aqueous-phase S(IV)→S(VI) oxidation rate catalyzed by dissolved Fe(III), from Seinfeld & Pandis (2006), Atmospheric Chemistry and Physics, 2nd ed., Chapter 7, Eq. 7.92. The component reports a single diagnostic, the Fe(III)-catalyzed oxidation rate R_Fe = k·[Fe(III)]·[S(IV)]/[H+], for the low-pH (pH 0-3.6) regime: the rate rises in proportion to the dissolved-iron catalyst and the total S(IV) substrate, and falls inversely with the hydrogen-ion concentration. Migrated from Aerosol.jl SulfateFormationFe. Purely algebraic: no differential states, one observed output and an empty equations array.

ModelingToolkit implementation of the S(IV) → S(VI) aqueous-phase oxidation rate catalysed by O2 with Fe(III)/Mn(II) synergism, from Seinfeld & Pandis (2006), Atmospheric Chemistry and Physics, 2nd ed., Chapter 7, Section 7.5.5, Eq. 7.102. The component reports the three additive contributions to the catalysed oxidation rate of dissolved S(IV) — a Mn(II)-only term (k_Mn·[Mn(II)]·[S(IV)]), an Fe(III)-only term (k_Fe·[Fe(III)]·[S(IV)]), and a synergistic term (k_FeMn·[Mn(II)]·[Fe(III)]·[S(IV)]) that is greatly enhanced when both transition metals are present — together with their sum R_FeMn. Migrated from Aerosol.jl SulfateFormationFeMn. Purely algebraic: no differential states; the four rate outputs are algebraic states defined by four equations.

Aqueous-phase S(IV)→S(VI) oxidation rate by hydrogen peroxide — Seinfeld & Pandis (2006), Atmospheric Chemistry and Physics, 2nd ed., Chapter 7, Section 7.5.2, Eq. 7.84. Hydrogen peroxide is the dominant oxidant converting dissolved sulfur(IV) (SO2·H2O, HSO3-, SO3^2-) to sulfate in cloud and fog droplets at low pH, where the competing O3 oxidation pathway is slow. The rate law R_H2O2 = k·[H+]·[H2O2]·[HSO3-]/(1+K_eq·[H+]) is first-order in aqueous H2O2 and in bisulfite, rises with acidity, and saturates toward k·[H2O2]·[HSO3-]/K_eq at very high [H+]. Because the equilibrium bisulfite concentration itself scales as 1/[H+], the overall H2O2 oxidation rate (when [HSO3-] is tied to gas-phase SO2) is famously almost pH-independent across cloud-water pH 2-6 — but within this standalone component [HSO3-] is an independent input, so the rate computed here does scale with [H+]. Migrated from Aerosol.jl SulfateFormationH2O2.

Mn(II)-catalyzed aqueous-phase S(IV) oxidation rate (sulfate formation) — Seinfeld & Pandis (2006), Atmospheric Chemistry and Physics, 2nd ed., Chapter 7, Section 7.5.4, Eq. 7.101. In cloud and fog droplets, dissolved S(IV) (SO2·H2O, HSO3⁻, SO3²⁻) is oxidized to S(VI) (sulfate) by dissolved O2, a reaction strongly accelerated by transition-metal catalysts. This component implements the manganese(II)-catalyzed pathway in the low-S(IV) (< 1 µM) regime, where the rate law R_Mn = k0·[Mn(II)]·[S(IV)] is first-order in both the Mn(II) catalyst and the total dissolved S(IV). (In the high-S(IV) regime, > 100 µM, the rate instead becomes zero-order in S(IV) and second-order in Mn — a separate regime not implemented here.) The Mn(II) pathway, together with the O3, H2O2, and Fe(III) pathways and the Fe/Mn synergistic term, controls how fast SO2 is converted to sulfate aerosol within clouds — a dominant route for atmospheric sulfate production. Migrated from Aerosol.jl SulfateFormationMn.

Aqueous-phase S(IV)→S(VI) oxidation rate by dissolved ozone — Seinfeld & Pandis (2006), Atmospheric Chemistry and Physics, 2nd ed., Chapter 7, Section 7.5.1, Eqs. 7.79-7.80. Dissolved S(IV) (sulfur in the +4 oxidation state) partitions in cloud and fog droplets among three species — un-ionized SO₂·H₂O, bisulfite HSO₃⁻, and sulfite SO₃²⁻ — set by the S(IV) acid-dissociation equilibria. Each is oxidized to S(VI) (sulfate) by dissolved ozone through a parallel second-order channel, and the total oxidation rate is their sum: R_O3 = (k0·[SO₂·H₂O] + k1·[HSO₃⁻] + k2·[SO₃²⁻])·[O₃(aq)], first-order in each S(IV) species and first-order in dissolved O₃. The three rate constants climb steeply with the degree of ionization — k0 = 24, k1 = 370, k2 = 1.5×10⁶ m³ mol⁻¹ s⁻¹ — so the channel is strongly pH-dependent: at high droplet pH the sulfite term dominates and oxidation is fast, at low pH it is slow. The S(IV)+O₃ pathway is one of the principal in-cloud sulfate-production routes. Migrated from Aerosol.jl SulfateFormationO3.