How many nm do solar radiation (UV) become dangerous?
Between 200 and 320 nm poses signficant health hazards if not effectievly blocked by stratospheric ozone.
How is ozone formed? And how can it be destoyed?
By reactions intiated by the splitting of O2.
By various catalytic cycles involving nitrogen, chlorine and bromine.
How did the ozone layer come about?
It was a byproduct of the evoloution of photosynthesis and the rise of atmoispheric oxygen.
What 3 disitnct spectral ranged do UV radiaiton between 200 - 400 nm split into? Which one is the most dangerous?
Longest: UVA (320-400nm)
Middle: UVB (290-320nm)
Shortest: UVC (200-290nm)
What does it mean if the UVA has a low ozone absorbtion coefficent?
And what is the result of it?
That the ozone does not absorb much UVA radiaiton.
Most UVA radation passes through the atmosphere and reaches Earth’s surface.
Which radation is the biggest concern for us?
UVB
if the UVB flux increases it can be detrimental for awuatic life, cause skin cancer and sunburn.
What is the reason for the stratoshpere exisitng?
The reason the stratosphere exists is because the absorption of solar UV radiation by ozone heats the air and causes the temperature to increase with altitude.
Two ways to measure the vertical distribution of ozone?
- Remote sensing from satellites
- In situ measurements from ozonesondes. (Balloon borne instruments)
What is the unit called that measures the ozone column?
Dobson unit
Where are ozone column depths typically highest and lowest?
Highest: mid-to-high latitudes
Lowest: Over the equator
Where does the greatest production of ozone occur?
In the tropics, where the solar UV flux is the highest.
Why is it easier to get sunburnt in Florida 25-30* than in NY 43*?
- Sun is higher in the sky at low latitudes.
- Ozone column depth is smaller in the low latitudes.
How many % ozone is in the troposhere? And what does it do there?
10%
Provides a source of oxidizing radicals that help cleanse the lower atmosphere of pollutants such as CO and SO2.
Hur formas ozon?
- Syrgas splittras av UV photon
- Får två fria syre-atomer
- Dessa fria syre atomer reagerar med varsin syrgas molekyl och bildar ozon.
O + O2 –> O3
Which UV radiation is required to protolyze O2 to ozone?
UV radiaiton with wavelength shorther than 240nm.
How can an ozone molecule be photolyzed/destroyed?
By the absorption of another photon.
O3 + photon –> O2 + O
O + O3 –> 2 O2
What is odd oxygen?
Odd oxygen include all pure oxygen-containing atoms or molecules that have a odd number of oxygen atoms. Exempel O och O3
Name 3 radicals in the catalytic cycle. What do they do?
Nitrogen, Bromine and Chlorine
They provide a faster way to destory odd oxygen.
Which of the 3 radicals have a antropogenic source?
Chlorine and Bromine
Where is the most striking evidence of ozone depletion?
In antartica there’s an ozone hole that forms each year during october.
What are the particles called that are involved in the formation of the ozone hole?
Polar stratoshperic clouds PSCs
What 2 ways do PSCs alter the chemistry of the lower stratosphere?
- Breaking the coupling between
the odd nitrogen and chlorine cycles and allowing free chlorine to wreak havoc on the
ozone layer. - by providing surfaces on which heterogeneous reactions can occur
Why does the Arctic stratosphere behave differently than the Antartic stratoshpere?
because the wintertime polar vortex is not as well developed or long-lasting in the Arctic.
What happens when the air sinks in the polar Vortex?
When air sinks in the vortex:
It removes odd nitrogen compounds from the polar stratosphere.
These nitrogen compounds normally help limit ozone destruction.
Because they are removed and not replaced, conditions become ideal for chemical reactions that destroy ozone.
