6.3 Photochemical Smog

Causes of increased urban air pollution in the troposphere

industrial emissions (of gases)

pop growth

• more ppl → more cars → more industry → more pollution

increase in affluence

• money to spend on more stuff (ex: more cars)

Air Pollution

Linked to health problems + premature death

BRICS

• have more deaths than rest of the world

OECD (org of economic cooperation)

• US, Canada, Mexico, most of Europe, Australia, New Zealand, CHile

OECD countries hv LESS deaths due to air pollution than BRICS + rest of world bc…

• more resources to control emissions

• better health care for treatment

• reliant on India, China for goods

• Chile: less pop, diff lifestyle

Measuring Air Pollutants

• ug/m³ in a 24 hr period or annual mean

• WHO standards are strictest, then EU, then US

• what’s measured

  • PM10, PM2.5 = particulate matter

  • O3, Nitrogen Dioxide (NO2), Sulfur Dioxide (SO2)

Fossil Fuel Combustion (primary cause of air pollution)

Releases CO2, H2O(g), SO2, NOx, PMs

• primary pollutants (direct output)

• sources = stationary (factory), mobile (car), natural (volcano)

Emitted as smoke + soot

CO + hydrocarbons when combustion is incomplete

Primary pollutant react to form secondary pollutants

• NOx + SO2 → acid rain react w/ water

• Ozone = NO2 + HCs react w/ sun

Impacts of air pollution

CO2 + H2O = GHGs, can increase global T

SO2 from coal + oil combustion

• respiratory + eye irritant

• cause of acid rain

• emissions concentrated in URBAN AREAS

  • higher rates of asthma

Nitrous Oxides (NOx)

from FF combustion

highest where automobile use is high (NOT ELECTRIC CARDS!! ONLY PETROL POWERED CARS)

creates a hazy yellow, brown gas

impacts

• respiratory irritant

• contributes to acid rain or ground lvl ozone

• precursor to photochemical smog and acid rain

Particulate Matter

FF combustion

smoke/soot

PM10 <= 10 um

• can increase CV disease (asthma)

PM2.5 <= 2.5 um

• can travel deep in the lungs

Photochemical Smog

Forms when sun catalyzes series of chem rxns b/t NOx + VOCs

• MAKES O3, PAN, aldehydes

• VOC = volatile organic compounds

  • carbon based

• NOx comes from industrial, power station, vehicle emissions

• VOCs from industrial + vehicle emissions + solvents (from forest fires)

Tropospheric Ozone

SECONDARY POLLUTANT

Influencing factors of photochemical smog

High emissions of FF → more pollution → more smog

• industrial emissions (high/low industry)

• population size (more ppl → more pollution)

• main transport in an area (petrol powered cars/buses VS electric/hybrid)

High sunlight (high O3 production)

• sunny days increase production

Calm winds (pollutant dispersion won’t happen)

Dry weather (rain can knock pollutants down)

Topography (valleys can trap pollutants)

• topography causes thermal bc its not easy for wind to blow smog out of a valley

Thermal inversion

Thermal Inversion

warm layers over cold air (cold, warm, cold) → traps pollutants closer to the ground

more likely to be inverted in the morning (6 AM)

more common in VALLEYS + dry sunny places with little wind

Impacts of Tropospheric Ozone

ground level ozone

• highly reactive

• economic loss

  • affecting human health (irritates eyes, respiratory illness)

  • damaging leaf cells of plants (reduced productivity)

  • damaging materials like plastic + rubber

when wind blows, pollution can clear in one place, but then it goes elsewhere

Policies @ many levels

International

• cooperation b/t nations to create agreements, covenants, treaties to regulate air pollution

National

• a single nation creates laws to regulate air pollution

Local

• small municipalities w/in a country that regulates air pollution

Pollution reduction policies

ALTER human behavior

• edu campaigns (why emissions are bad)

• economic strategies (incentives like rebates to buy electric cars, or reduce electricity use)

LEGISLATION

• laws that limit emissions of PM + NOx + SO2

MITIGATION/Restoration

• EXPENSIVE: clean up + restoring damaged areas

Human behavior strategies

Education campaigns

• inform abt pollution damage

• inform how to reduce emissions

Individual practices

• energy efficient appliances

• turn things off when not in use

• modify homes (better insulation)

• decrease consumption

• buy local

• walk, bike, public transport

• hybrid/electric vehicles

• decrease consumption of electricity (including fast fashion)

• carpool

Economic incentives to alter behavior

“pollution tax” (mostly industry)

subsidies for

• new tech

  • ex: solar panels

• to promote renewable energy

• public transport

Tech changes

requires time, money, research

catalytic converters → reduce pollutants

• part of car’s exhaust system

• mandatory since 1970s

• SMOG test

• reduce pollutants from FF combustion

• makes chemicals less harmful

increase efficiency of vehicles + appliances

alternative energy sources (solar, wind)

Legislation

Intl agreements

• Gothenburg Protocol: lessen ground level ozone, acidification, reduce emissions of other major pollutants

Legislation to set emissions targets, stronger standards

Building regulations (standards for energy efficiency)

Planning regulations

• bicycle paths

• where to put industry + power plants

• road lanes for public transportation (PT)

• vehicle free zones
  

Mitigation + Restoration

• “scrubbers” to filter emissions prior to discharge to remove primary pollution

  • on industrial smokestacks

• reforestation

  • plant trees/reestablish forests