Heterogeneous nucleation of a common atmospheric aerosol: Ammonium sulfate

Abstract

Abstract. Natural and anthropogenic aerosols have a direct impact on the earth's radiative balance. Many of the common atmospheric aerosols contain hygroscopic salts and therefore their physical state and composition are sensitive to the relative humidity. The phase of the aerosol particle will dramatically affect the relative rates of atmospheric reactions, and radiative properties such as scattering and optical activity. In order to understand these atmospheric processes and provide accurate input for global modeling, it is imperative that these phase transitions be well defined. It is thought that the degree of metastability is influenced by the presence of foreign particulate matter. These solid impurities are predicted to reduce the barrier of nucleation by providing a surface upon which heterogeneous nucleation can be catalyzed. We report the results of CaCO3 and BaSOn solid impurities on the efflorescence of (NHn)2SOa-H20 micro-droplets. The results show that both solid impurities act as catalysts for heterogeneous nucleation by causing a decrease in the degree of metastability at the efflorescence point. BaSOn does not prove to be significantly more efficient than CaCO3 in spite of having the same crystalline structure and similar lattice parameters as in (NH4)2SO4.

Emissions of volatile organic compounds originating from UK livestock agriculture

“…Dairy cows were calculated to be the greatest ruminant contributors to the atmospheric flux of DMS. This may explain some of the unknown DMS of terrestrial origin that was previously thought to be small, but still important, because DMS is oxidised to sulphuric acid, which initiates cloud formation via particle nucleation 20…”

Single-particle levitation system for automated study of homogeneous solute nucleation

“…1 Electrostatic levitation has therefore found many applications in aerosol and materials research, including investigations of aqueous solution thermodynamics and crystal nucleation kinetics. [1][2][3][4][5][6][7][8][9][10][11][12] Several researchers have recently employed electrostatic levitation to quantitatively investigate crystal nucleation kinetics in a variety of chemical systems. Nucleation is a stochastic process; when a supersaturated or supercooled state is created, nucleation occurs after a delay or incubation time.…”

Clear-air lidar dark band

“…exhibits difference values for the deliquescence and efflorescence relative humidity (Sjogren et al, 2007); this hysteresis behaviour ultimately determines a less efficient evaporation process (Seinfeld and Pandis, 2006). More specifically, when RH decreases, the solution droplet starts reducing in size through the evaporation of the previously taken up water at the efflorescence point, which is found at a much lower RH value than the deliquescence point (Oatis et al, 1998).…”