7 Flashcards
troposphere
the lower regions 0-15km
the warmest (av about 15 C)
lower amounts of O3 but still some present
tropopause
the boundary between the troposphere and the stratosphere. the temp here is -56 C
stratosphere
between 15-50 km
contins chemical compouns responsible fro protecting life of earth from harmful UV rays
contains the highest concentration of O3 (in a parabola)
how does absorbtion by O2 or O3 reduce sunlight in the atmosphere
no so much sunlight, but the type of radiation received at the surface. Compound will absorb UV light. where the amount absorbed, means there is less able to be transmitted or satered into other directions
what is the potenital impact of the absence of stratospheric O3
where there is a lack of O3, there can be holes. in these holes, there is no compounds that are able to absorb the incoming radiation. this means that a broader range of UV light (which we don’t have ample protection to) is more likely to reach the surface. this can react with tropospheric compounds or induce harm to humans (DNA damage, cataracts (eye condition) or crop failure)
this will increase the UVc and UVb thatreaches the surface
hat are the 3 catylitc mechanisms for stratosphereic O3 depletion
OH
NO
and reactive halogens like Cl and Br
what are CFC
chlorofluorocarbons,which only contain C, F and Cl
they are non toxic, flammable or bioaccumalitve. but are highly volatile
they were commonly used in cooling system in the 1940
why do CFC induce stratospheric O3 depletion
they are a source of reactive ClO and No2 (from the reaction XO) which are active, short-lived species
in the stratosphere the compounds will mix to make ClNO3, a long-lived reservoir species that can hold the active species for prolonged periods of time, allowing them to accumulate in the stratosphere. (they can be replaced at any time so O3 is constantly degraded)
explain dobson units
the unit for expressing O3 abundance in a column
equal to 10^-5. of O3 at 273.15K and 1atm of pressure
equivalent to 2.69 x 10^ 16 molecules. cm^2
where the height of the column will express how much O3 is present at specific conditions
active vs inactive chlorin reservoir
why do O3 holes form at the N and S poles
due to an increase in halogen chemistry formed from the interaction of Hcl and ClNO3 on polar stratospheric clouds.
HCl + ClNO3 –> Cl2 and HNO3
Cl2 + UV–> 2Cl radicals that will break O3
what is the Montreal protocol and why is it important
voted to phase out CFCs and HCFCs and halons. they began preforming regular ozone assessments
they phased out hydrogen contend chlorinated and brominated compounds .
over time this was effective as the increase in atmospheric CFC plateaued and O3 hole began to repair itself
what are the main elecemtn in the atmos what are thier []
N2= 78%
O2= 21%
Ar= 9%.
why isnt H2O included in the list of atmospheric compounds
bc the [] is always changing
what are UVc rays
200-280nm
