Mass_balance

Coupled gas-phase and aqueous-phase mass balance for cloud droplet chemistry. Tracks the time evolution of bulk gas-phase partial pressure and aqueous-phase concentration, including gas-to-aqueous mass transfer and aqueous-phase chemical reaction (Seinfeld & Pandis 2006, Ch. 12, Eqs. 12.122-12.123). Migrated from Aerosol.jl src/aqueous_transport.jl:112.