Week 6 Flashcards
(44 cards)
What are aerosols?
A colloid of fine solid particles/liquid droplets in air/another gas originating from condensation of gases from the action of wind on the Earth’s surface
Methods of transformation for aerosols?
- Enrichment
- Gas to particle conversion (nucleation/condensation)
- Coagulation
Describe the process of coagulation
Particles with d<1um are in constant Brownian motion meaning they collide and stick together
Classification- size of aerosols
Aerosols range from nm (10^-9 m) to mm (10^-3m)
Mechanical generation of aerosol particles?
- Spore ejection by common moss
*Wind - blown soil dust - Cellular and protein particles
Why does sea salt concentrations in the atmosphere vary?
Due to wind speed, wind and wave action over ocean
Where does dust orginate?
Arid and semi arid regions
Lifetime of dust
Weeks
What does emission of fine and coarse dust aerosols depend on ?
Surface properties and wind speed
Examples of biological aerosols?
Seeds, pollen , spores, fungi, viruses, bacteria
How does marine organic material disperse into the atmosphere through aerosols?
Air bubbles are generated at the water surface through surface winds
Bubble bursts forming film droplets- carrying organic matter contained in the surfactant layer into the atmosphere
Drivers of biological aerosol particles?
- Anthropogenic activity
- Humidity/wetness
- Vegetation cover
- Wind
- Temperature
- Biological activity
Process that can change the composition of aerosols in air from composition of aerosols at origin
Enrichment
Enrichment factor EF[X] equation for element X in aerosols?
EF[X]= ([X]aerosol/[Ref]aerosol)/ ([X]source/[Ref]Source)
What may particles in the atmopsphere condensing lead to ?
- Condensing onto existing particles- increasing the mass but not the number of aerosols
- To from new particles
When would particles condense onto existing particles?
If the SA of the existing aerosols is high and the supersaturation of gases is low
What to new particles formed from gases in the atmosphere condensing form?
Aitken nucleus size aerosols
What are Aitken nucleus size aerosols?
Aitken nuclei are very small atmospheric aerosol particles, typically with diameters between 0.01 µm (10 nanometers) and 0.1 µm (100 nanometers)
Major chemical species involved in aerosol formaiton?
S, N and organic carbonaceous material
What is gas-particle equilibrium
Equilibrium partitioning is always at the gas particle interface
What is partitioning between gas and aerosol phase determined by?
Their free energies
Gas - particle equilibrium equation
k=[X(a)]/Px
Equilibrium constant= Concentration of X in particle phase/partial pressure of X
What does henrys law constant (K) increase with?
Decreasing temperature- K doubles every 10K temp decrease
Why is the particle equilibrium of non aqueous gases harder to quantify?
Uncertainty in composition of particle phase
