CHAPTER 2 - EXAMPLES OF AIR POLLUTION PROBLEMS

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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?)

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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