Question 4Explain how information on changes in atmospheric ozone concentrations is obtained

Anita and Lily

Ozone (OOzone (O33))Pale blue and highly reactive gas with a

pungent odourAllotrope of oxygenTroposphere = 10%Stratosphere = 90%In the stratosphere it acts as a primary

UV radiation shield

•Vast majority of the atmospheric ozone occurs in the stratosphere

Photochemical SmogPhotochemical SmogN2(g) + O2(g) 2NO(g) due to the high

temperature in engines2NO(g) + O2(g) 2NO2(g) released from

car exhaust and oxidised in airNO2(g) + UVlight NO(g) + O (g)

forming oxygen radicalO (g) + O2(g) O3(g)

Causes for ‘ozone hole’Causes for ‘ozone hole’Thinning of the ozone layerCFCs- They remain in the troposphere for

decades and eventually find their way to the stratosphere

- CCl3F(g) + UVlight Cl● (g) + CCl2F● (g)

CCl2F● (g) + UVlight Cl● (g) + CClF● (g)

- Cl● (g) + O3(g) ClO● (g) + O2(g)

- ClO● (g) + O● (g) O2(g) + Cl● (g)

Halons- Produces bromine radicals which are

even more detrimental than Cl radicals- Br● (g) + O3(g) BrO● + O2(g)

• Carbon Tetrachloride- Solvents• Cl2 + u.v light 2Cl

- Can destroy ozone in the same way as Cl atoms from CFC’s

Effects of the ‘ozone hole’Effects of the ‘ozone hole’Cellular damage e.g. sunburn on

mammalian skinChanges in plant growthPlankton and the ecosystemTerrestrial plants, in particular

agricultural cropsSkin cancerDamage to the immune system (diseases)Respiratory problems

Ways to obtain changes in Ways to obtain changes in atmospheric ozone concentrations atmospheric ozone concentrations UV SpectrophotometersUV light from satelliteHigh-flying aircraft BalloonsLasers fired from ground