Acidic particles hygroscopic growth

The interaction between molecules in the gas phase and the surface of particles and droplets in the atmosphere is central to important phenomena such as ozone depletion in polar areas, hygroscopic growth of particles, aging, acid rain, particle growth and cloud droplet formation. 

Acid droplets absorb ammonia and become partially neutralized as they pass along the respiratory tract. Cocks and McElroy (1984) extended the work already discussed (Cocks and Fernando, 1982) on the hygroscopic growth of particles to model the growth and neutralization of acid aerosols. Before considering the results of the Cocks and McElroy (1984) study, two difficulties identified and dealt with by these authors should be examined ... 

For the results shown in Table 13, the model has included sufficient ammonia to bring about complete neutralization of the acid droplets in the air. As the initial relative humidity was high (99.5%), no hygroscopic growth of the particles occurred. Complete neutralization of 5 qin droplets would be expected in 3 s. The capacity of the ammonia present to neutralize all of the acid present should be contrasted with the extent of neutralization possible had the ammonia concentration been 50 pg m 3. 

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