EARTHSS 23 Lecture 4: ESS23 Lecture 5,6,7
10 Mar 2017
School
Department
Course
Professor
Lecture 5
Schonbein: electrolysis of water at the U of Basel that Schonbein first began to notice a
distinctive smell, greek work ozein “to smell”
Radical: atoms, molecules with unpaired electrons, unstable in other words “very reactive”
Importance of Hydroxyl: remove trace gases from the atmosphere, net production of ozone, most
important oxidant (atmospheric cleanser), O3 and NO3 are also important oxidants
Dalton’s law of partial pressure: total air pressure equals the sum of partial pressures of
individual gases in the air
Background troposphere: inorganic gases (nitrogen compounds, CO, SO2), long-lived light
(small) organic gases, naturally-emitted short-lived heavy organic gases
Polluted air: inorganic gases, short-lived light and heavy organic gases
Lecture 6
Photostationary State Ozone, Photochemical Smog Formation
Ozone from Carbon Monoxide, Methane, Ethane, Formaldehyde
Methane is a volatile organic compound (VOCs) but not a reactive organic gases (ROGs)
ROG is subset of VOC, only methane is not a ROG
Octet Rule: a chemical rule of thumb that states that atoms of main group elements tend to
combine in such a way that they each have eight electrons in their valence shell
Lifetime of Chemical species towards specific oxidants
(the chemical lifetime of isoprene) = 1/kOH Isoprene[OH])
Daytime removal of NOx “Nitric Acid Formation”
Daytime Removal of Peroxyradicals “Peroxide Formation”
• Too much NOx may deplete OH in the atmosphere
• Too much ROGs (VOCs) may deplete HO2 in the atmosphere
Lecture 7
Light Attenuation (reduction) processes
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