B4.2 - Troposphere

What is an aerosol

tiny solid or liquid particles suspended in air

Natural sources of aerosols

sea spray (sea salt)
Dust storms (mineral dust)
volcanoes (sulfates)

Anthropogenic sources of aerosols

fossil fuel combustion (sulfates, nitrates)
incomplete combustion (soot)
industrial processes (metals and complex particles)

what is a primary aerosol

emitted directly from the source

what is a secondary aerosol

formed in the atmosphere

what controls aerosol residence time

particle size (larger ones affected by gravity)

removal processes (wet/dry deposition)

atmospheric conditions (vertical mixing, cloud formation)

what is wet deposition

Removal through precitipation processes like clouds, rain, and snow

what is dry deposition

removal through the Earth’s oceanic and terrestrial surfaces (water, soild and vegetation) in the absence of precipitation

what kind of cycles should be considered in the troposphere

null cycles (not catalytic cycles)

what is the only species H₂O will react with

O (¹D)

What species are present in the day

HOx, NOx (polluted), O3

What species are present at night

NO3 (polluted), O3

What will RO2 react with

NO (forms NO2 + RO)

what will RO react with

O2 (forms HO2 + carbonyl or smth)

What will CO react with

HO2 (forms H which reacts with O2 to form another HO2)

importance of VOCs, HOx and NOx in the production of ozone in the troposphere

• NOx/O3 forms a null cycle (NO + O3 → NO2 + O2) when VOC = low (region B)

• need HOx to break null cycle and use NO2

• CO + HO + O2 → HO2 + CO2

• need photolysis of NO2 to form O

• when [NOx] is low, rate of HO2 + NO → NO2 + OH is small

are atmospheric reactions main kinetic or thermodynamically driven

kinetic

where will O3 likely attack if you have a hindered and non-hindered alkene

non-hindered (kinetic driven)

why draw the squiggles in ozonolysis mechanism

shows different ways the ozonide can break, dar 2 in different colours to show the 2 potential FIRST GENERATION products

Crigee intermediate

Ozonolysis product, the RO2 one

in increasing rate coefficient, list the species that can oxidise NMVOCs

O3, NO3, OH, Cl
Only OH and Cl interact with 1 C species