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Water uptake and equilibrium sizes of aerosol particles at high relative humidities: Their dependence on the composition of the water-soluble material

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Abstract

Equilibrium water uptake and the sizes of atmospheric aerosol particles have for the first time been determined for high relative humidities, i.e., for humidities above 95 percent, as a function of the particles chemical composition. For that purpose a new treatment of the osmotic coefficient has been developed and experimentally confirmed. It is shown that the equilibrium water uptake and the equilibrium sizes of atmospheric aerosol particles at large relative humidities are significantly dependent on their chemical composition.

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Abbreviations

A :

proportionality factor

a w :

activity of water in a solution

c p v :

specific heat of water vapour at constant pressure

c w :

specific heat of liquid water

f :

relative humidity

l w :

specific heat of evaporation of water

M i :

molar mass of solute speciesi

M s :

mean molar mass of all the solute species in a solution

M w :

molar mass of water

m 0 :

mass of an aerosol particle in dry state

m i :

mass of solute speciesi

m s :

mass of solute

m w :

mass of water taken up by an aerosol particle in equilibrium state

m :

total molality=number of mols of solute species in 1000 g of water

m i :

molality of solute speciesi

m k :

total molality of a pure electrolytek

O(m 2):

remaining terms being of the second and of higher powers ofm

p + :

standard pressure

p′ :

total pressure of the gas phase

p″ :

pressure within a droplet

p 1,p 2,p 3 :

coefficients in the expansion of φM

p 1i, p2i, p3i :

specific parameters of ioni

p s :

saturation vapour pressure

p′ w :

water vapour pressure

R w :

individual gas constant of water

r :

radius of a droplet

r 0 :

equivalent volume radius of an aerosol particle in dry state

T :

temperature

T 0 :

standard temperature

T 1 :

temperature of the pure water drop in the osmometer

v w :

specific volume of pure water

z i :

valence of ioni

αi :

relativenumber concentration of ioni in a solution

γ:

correction term due to the adsorption of ions at liquid-solid interfaces

γ:

activity coefficient of solute speciesi in a solution, related to molalities

ΔI :

bridge current

ΔT :

temperature difference between solution and pure water drop in the osmometer

η:

exponential mass increase coefficient

μ w :

specific chemical potential of water vapour

μ w :

specific chemical potential of water

μ′ 0 w :

specific chemical potential of pure water vapour

μ″ 0 w :

specific chemical potential of pure water

ρ0 :

density of an aerosol particle in dry state

ρw :

density of pure water

σ:

surface tension of a droplet

σ0 :

surface tension of pure water, i.e., at infinite dilution of the solute

ϕ:

osmotic coefficient

ϕk :

osmotic coefficient of a solution of a pure electrolytek

ϕk :

osmotic coefficient of a solution of a mixed solute

ϕM :

fugacity coefficient of water vapour

ω:

s i=1 αi z 2 i

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This work is part of a Ph.D. thesis carried out at the Meteorological Institute of the Johannes Gutenberg-Universität, Mainz.

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Thudium, J. Water uptake and equilibrium sizes of aerosol particles at high relative humidities: Their dependence on the composition of the water-soluble material. PAGEOPH 116, 130–148 (1978). https://doi.org/10.1007/BF00878988

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Key words

  • Condensation nuclei
  • Aerosol particles
  • -water uptake of
  • -growth of