Atmospheric Processes: Air Pollutants Flashcards
The Atmosphere
o Made up of gases: nitrogen, oxygen, argon, neon, helium, hydrogen, xenon
o Ability of the atmosphere to disperse pollutants depends on:
• Average wind speed and direction
• Temperature profile
• Precipitation etc.
o Stability of atmosphere relates to temperature profile
• Stable equilibrium:
• Rock inside a hole: if moved, it will return to original position
• Unstable equilibrium
• Rock on top of a hill: if moved, it will escape
o Greenhouse gases are present in the troposphere
Atmospheric Stability
o Adiabatic rate < environment lapse rate:
• Air parcel lifted into atmosphere is colder & heavier than air around it and hence, returns to surface
o Adiabatic rate > environmental lapse rate:
• Air parcel lifted into atmosphere is warmer and lighter that air around it and hence, air parcel would accelerate away from surface
o Fog: stable
• Colder and more dense at bottom, warmer and less dense at top
o Clouds: unstable
• Colder and more dense at top, warmer and less dense on bottom
Atmospheric Inversions
o Inversion layer: stable
o Mixing layer: smoke will not rise above into the stable layer, and hence, pollutants cannot escape
Influence of Wind
o Windy night: hot & cold mixed together
o Calm night: pollution is higher as hot & cold are separated
Subsidence Inversions
o Compression of falling air causes heating
o High pressure = clear weather
Global trends in air pollution
o Large cities
• Strict regulations, low pollution
o Developing countries
• Levels are high and will most likely increase with further development
Air Quality Index
Concentration expressed as percentage of relevant standard:
Index= (pollutant concentration)/standard × 100
> 100: pollutant has exceeded standards
< 100: pollutant is within standards
Primary Air Pollutants
o Carbon monoxide (CO)
• Colourless, odourless, tasteless
• Produced by incomplete combustion of hydrocarbons
• Can cause headaches, dizziness and death
o Nitrogen oxide (NO) and nitrogen dioxide (NO2)
• NO is harmless, NO2 is a respiratory irritant
• NO2 reacts in atmosphere to produce smog and nitric acid
o Volatile organic compounds (VOCs)
• Easily vaporised hydrocarbons
• Form photochemical smog
• Some are carcinogenic (can cause cancer)
o Particulate matter (PM)
• Main components: sulphate, nitrates, ammonia, sodium chloride, carbon (soot), mineral dust, water
• Standards based on PM10
o Sulphur dioxide (SO2)
• Mainly comes from electricity generation and metal manufacturing
o Lead
• Mainly comes from roads and metal manufacturing/mining
o Photochemical smog
• Formed by VOCs + nitrogen oxides + sunlight
• Contains chemicals: ozone, formaldehyde, peroxyacetyl nitrate
• Effects: eye/nose/throat irritation, respiratory constriction, headache
o Carbon dioxide
o Methane
Secondary Pollutant
o Ozone (O3)
• Good ozone: in our protective ozone layer (in stratosphere) – protects planet from the sun
• Bad ozone: in the troposphere – strong photochemical smog potential
