EXAMPLES OF AIR POLLUTION PROBLEMS CHAPTER 2 EXAMPLES OF AIR POLLUTION PROBLEMS

EXAMPLES OF AIR POLLUTION PROBLEMS Classical urban Air Pollution Modern urban Air Pollution Acid rain Greenhouse effects Ozone depleption

Classical urban Air Pollution "smog" = smoke + fog (London, 1952) sulphur, soot, water vapour => acid aerosol

Modern urban Air Pollution Stagnant air Continuing emissions "summer" (photochemical) smog: NO, NO2, CxHy, UV-rad: ==> O3 (reactions worked out on blackboard) Winter (cold weather) smog: fine or ultra-fine particles ==> health effects Mixture is different in different cities Traffic important source Toxicological mechanism still unknown Health effects even at low concentrations (from 40 mg/m3?)

Acid Rain Dry and Wet deposition of (potentially) acidifying substances onto the earth's surface. * so: not just rain!

ACID RAIN FORMATION

Acid Rain Process

Acidifying compounds SO2 and NOx (direct)  H2SO4 and HNO3 NHx (indirect by nitrification): (NH4)2SO4 + 4O2  2HNO3- + H2SO4 + 2H2O

Effects of acid rain Plant injury (direct by SO2, NH3, (NO), NO2) Change in mineral balance in soils (=> heavy metals) Acidification of waters

Effects of acid rains

Deposition dry deposition (direct from air to surface): proportional to concentration important close to source (areas) wet deposition (by rain, snow, hail, etc.) rain cloud "washes" air mass origin of air mass important only when it rains occult deposition (direct from fog or clouds) only in areas with many fogs (mountainous areas)

Critical loads concept That amount of (total) deposition that an ecosystem can "handle" for a prolonged time

Geographic distribution of acid rain

Greenhouse effects Radiation balance of the earth (figure 2.2) Incoming solar radiation (short wave) Outgoing black-body radiation (long wave - infrared) (figure) Temperature of earth is equilibrium Natural greenhouse effect Change in any term changes temperature

Projected temperature change

Radiative forcing Any change in the balance Greenhouse gases: CO2, CH4, N2O, CFC's, (O3) Increasing concentrations (figures) => enhanced greenhouse effect

Factors of importance Concentration increase rate Atmospheric lifetime ==> Global warming potential (Table 2.2 and 2.3)

Ozone depletion Ozone layer (20 - 50 km height; figure) Absorbs UV-B (figure 2.3) Thickness of ozone layer 30 km but 3 mm pure O3 at 100 hPa! 3 O2  2 O3 (UV-B radiation needed) NO2  NO + O (UV-A radiation) Four groups of substances interfere (eq. 2.15 - 2.22)

Ozone hole due to heterogeneous reactions: in Antarctic winter Polar Stratospheric Clouds collect chlorine compounds set free in Spring (September) eq. 2.17

Health Effects

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