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GEOG 221 (32)
Nancy Ross (14)
Lecture 4

GEOG 221 Lecture 4.4.docx

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GEOG 221
Nancy Ross

GEOG 221 Lecture 4.4  With more and more people living in cities, we have more smoh  Components of photochemical smog: o Internal-combustion gas engines operate at sufficiently high temperatures to generate NOx from N and O in air o Also produce CO and reactive hydrocarbons (RH) (=VOC’s)  Catalytic converters convert CO to CO2  A properly tuned engine reduces RH emissions o Also produce primary aerosol particulates  Photochemical smog o Primary pollutant from autos are NO and RH o These are converted in the presence of sunlight to the two most prevalent … o As the day goes on the atmosphere looks more polluted o Reduces the light levels  Requirements for smog o Source of primary pollutants  Transportation/industry emitting NOx and RH o Timing of emissions  Simultaneous release in morning  All primary pollutants have to be there to be converted to secondary pollutants o Distribution of sources  Concentration in urban centers or regions o Prevailing meteorology  Clear skies, warm temperatures with inversion (high pressure system)  Need sunlight  Near the ground, a lot of mixing; the depth of the mixing layer is the important thing; shallow mixing layer = lots of smog o Regional topography  Mountains or anything that blocks airflow; valleys o Geographical character  Vegetation emitting VOC’s; natural sources of particulates, etc. o Season  Secondary pollutant creation more efficient in summer; higher temperatures increase rates of formation o Urban demographics  Presence of old/poorly maintained vehicles; public will; tolerance of smog  A day in the life of smog o Time lag between emission of primary pollutants and creation of secondary pollutants o End of the day: pollutants deposited on the ground, settling out in the absence of energy required to produce pollutants (sun)  Pollution trends o Originally air quality legislation was concerned with pollution concentration reduction at ground level near point-source emission  taller stacks/chimneys o Results? Greater downwind dispersion!  Leads to transport over 100’s and 1000’s km  “Transboundary” air pollution  The Sudbury Superstack o Inco (now CRVD Inco) nickel smelter near Sudbury, ON o  Trends o Gradually legislation has forced a slow reduction in emissions  Reduction in deposition  Reduction in effects  o Clear Air Act in USA  SO2 are coming from localized, point emissions: easier to stop emissions  NOx harder to stop because the primary emission is caused by transportation o Canadian trends 1990-2010  57% reduction of emission of SOx: US-Canada emissions agreement; technological upgrades, pollution controls, plant closures, low-sulfur level  18% reduction of levels of NOX: cleaner auto tech and fuel, o Trends in Canadian air quality
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