title: Temperature-Dependent Henry's Law Constants of Atmospheric Amines.
abstract: There has been growing interest in understanding atmospheric amines in the gas phase and their mass transfer to the aqueous phase because of their potential roles in cloud chemistry, secondary organic aerosol formation, and the fate of atmospheric organics. Temperature-dependent Henry's law constants (KH) of atmospheric amines, a key parameter in atmospheric chemical transport models to account for mass transfer, are mostly unavailable. In this work, we investigated gas-liquid equilibria of five prevalent atmospheric amines, namely 1-propylamine, di-n-propylamine, trimethylamine, allylamine, and 4-methylmorpholine using bubble column technique. We reported effective KH, intrinsic KH, and gas phase diffusion coefficients of these species over a range of temperatures relevant to the lower atmosphere for the first time. The measured KH at 298 K and enthalpy of solution for 1-propylamine, di-n-propylamine, trimethylamine, allylamine, and 4-methylmorpholine are 61.4 ± 4.9 mol L(-1) atm(-1) and -49.0 ± 4.8 kJ mol(-1); 14.5 ± 1.2 mol L(-1) atm(-1) and -72.5 ± 6.8 kJ mol(-1); 8.9 ± 0.7 mol L(-1) atm(-1) and -49.6 ± 4.7 kJ mol(-1); 103.5 ± 10.4 mol L(-1) atm(-1) and -42.7 ± 4.3 kJ mol(-1); and 952.2 ± 114.3 mol L(-1) atm(-1) and -82.7 ± 9.7 kJ mol(-1), respectively. In addition, we evaluated amines' characteristic times to achieve gas-liquid equilibrium for partitioning between gas and aqueous phases. Results show gas-liquid equilibrium can be rapidly established at natural cloud droplets surface, but the characteristic times may be extended substantially at lower temperatures and pHs. Moreover, our findings imply that atmospheric amines are more likely to exist in cloud droplets, and ambient temperature, water content, and pH of aerosols play important roles in their partitioning.
authors.affiliation: Department of Chemistry, University of Colorado Denver, Denver, Colorado 80217, United States.
authors.forename: Chunbo
authors.initials: C
authors.lastname: Leng
authors.affiliation: Department of Chemistry, University of Colorado Denver, Denver, Colorado 80217, United States.
authors.forename: J Duncan
authors.initials: JD
authors.lastname: Kish
authors.affiliation: Department of Chemistry, University of Colorado Denver, Denver, Colorado 80217, United States.
authors.forename: Jason E
authors.initials: JE
authors.lastname: Roberts
authors.affiliation: Department of Chemistry, University of Colorado Denver, Denver, Colorado 80217, United States.
authors.forename: Iman
authors.initials: I
authors.lastname: Dwebi
authors.affiliation: Department of Chemistry, University of Colorado Denver, Denver, Colorado 80217, United States.
authors.forename: Nara
authors.initials: N
authors.lastname: Chon
authors.affiliation: Department of Chemistry, University of Colorado Denver, Denver, Colorado 80217, United States.
authors.forename: Yong
authors.initials: Y
authors.lastname: Liu