APES Unit 7: mid-unit test Flashcards
NO2
Broken down by sunlight into NO+O (free O+O2+O3)
VOCs
bind with NO and form photochemical oxidants.
carbon based compounds that volatize easily and participate in photochemical reactions
sources: gasoline, formaldehyde, cleaning fluids, oil based paints, even coniferous trees.
O3
Forms when NO2 is broken by sunlight and free O binds to O2.
This can cause respiratory irritation in the troposphere and damage plant stomata.
How Photochemical smog is made
sunlight drives O3 formation by breaking down NO2 into NO + O then free O atoms inds with O2.
Warmth - hotter atmosphere temperatures speeds O3 formation, evaporation, and thus smog formation.
Normal O3 formation
Sunlight breaks NO2 into NO +O
O bonds with O2 to form O3
At night, O3 reacts with NO to form NO2 and O2 once again, O3 levels drop overnight.
O3 formation typically peaks in afternoon when sunlight is most direct and NO2 emissions from morning traffic have peaked.
Morning commute leads to high NO2 levels from car exhaust.
Photochemical Smog Formation
Sunlight breaks NO2 into NO + O
O bonds with O2 to form O3
Without NO to react with O3 builds up instead of returning to O2 and NO2 overnight
VOCs bond with NO to form photochemical oxidants
O3 combines with photochemical oxidants to form photochemical smog
Factors that increase smog formation
more sunlight = more O3
warmer temperature, speeds evaporation of VOCs and reaction rates that lead to O3
High VOCs emissions
increased vehicle traffic
Why do Urban Areas have more smog?
More Traffic - more NO2
Hotter temps due to low albedo of blacktop
more VOCs due to gas stations and factories
more electricity demand, more NOx emissions from nearby power plants
Impacts of Smog
Environmental - reduces sunlight; limiting photosynthesis. O3 damages plant stomata and irritates animal respiratory tracts.
Humans - Respiratory irritation; worsens asthma, bronchitis, COPD, irritates eyes
Economic - Increased health care cost to treat asthma, bronchitis, COPD. lost productivity due to suck workers missing work or dying. decreased agriculture yields due to less sunlight reaching crops and damage to plant stomata.
Reducing Photochemical smog
Decreasing the number of vehicles on the road.
increase electricity production from renewable sources
Natural Gas power plants
Urban Heat Island Effect
Urban areas tend to have higher surface and air temperatures than surrounding suburban and rural areas due to lower albedo and less evapotranspiration.
Normal
Troposphere is warmer at the earths surface and cools as altitude rises and because warm air rises air convection carries air pollutants away from earths surface and distributes then higher into the atmosphere.
Temperature Inversion
A cool air mass becomes trapped near earths surface due to warm front moving in or due to hit urban surfaces cooling overnight while IR radiation absorbed during the day is still being released.
Effects of Thermal Inversion
Air pollutants trapped closer to earth
-respiratory irritation
-decreased tourism revenue
-decreased photosynthetic rate
Natural Sources of Air Pollutants
Lightning Strikes
Forest Fires
Plants
Volcanoes
