What's the difference between uptake and adsorption of gas into aerosols In the area of atmospheric chemistry, I have learned that the heterogeneous oxidation of SO2 is one of the important pathways for sulfate formation. The reactions of SO2 oxidation in mineral, soot particles have been confirmed. 

The adsorption or uptake of SO2 on the particle surface" is the initial process of the transformation. I have heard that adsorption is the surface-based process of gases or ions and create a film wiki reference.   

What's the difference between the adsorption and uptake processes?
Adsorption is adhesion of thin film of liquid or gas on solid substance and the host solid substance does not form chemical bond with deposited material. Uptake is entering of material into substance, end product of which is a solution. Uptake generally happens in liquid host substances but it is also possible for solid host substance to uptake the gas or liquid. 

In context of aerosols, the term adsorption is used when solid aerosol particles like dust, soot, ice, etc. are interacting with gases. The term uptake is used when liquid aerosol particle are interacting with gases. 

Reference
http://glossary.ametsoc.org/wiki/Adsorption