Air Pollution

What are air pollutants?

• gases and aerosols we add to atmosphere

• best known is smog– industrial - smoke and fog– photochemical - emissions + sunlight

• US has worked to control most air pollutants for many years

Why do we care?

• visual quality of the environment• vegetation, animals, soil• water quality• natural and artificial structures• human health

Major Air Pollutants

• sulfur oxides (SOx)• nitrogen oxides (NOx)• carbon monoxide (CO)• ozone and other photochemical

oxidants• volatile organic compounds (VOCs)• suspended particulate matter• lead (Pb)• air toxics

Many adverse effects from these pollutants

• chronic

• acute

• carcinogenic

Atmospheric inversions

Great London Smog of 1952

1000s died, much of countryaffected

Primary and Secondary Pollutants

• primary pollutants– those emitted directly into the air– hydrocarbons, particulates, SOx, NOx

• secondary pollutants– produced through reactions between

primary pollutants and normal atmospheric compounds

– ozone

What are sources?

• combustion of fossil fuels (coal, gasoline, diesel)– always incomplete combustion– stationary versus mobile sources– what comes out stack are primary pollutants– direct products of combustion

• USEPA measures ambient concentrations– 1970 Clean Air Act - taller stacks to meet

ground level standards

Sudbury, Ontario

1250 feet tall

US Emissions for 2011

Trends in Growth vs. Emissions

US emissions

Ozone (O3)

• good versus bad ozone– ground versus stratosphere

• ground level major pollutant– billions of dollars in crop losses each

year– respiratory hazard for human health

effect• not easy to reduce

Ozone (O3)

• secondary pollutant– photochemical oxidant

• source is VOCs, NO2, and sunlight

• most cities don’t meet ozone standards

• difficult (expensive) to reduce car emissions further

Ozone Monitoring

Ozone in the Midwest

Ozone Impact on Crop Yields

Acid rain (acidic deposition)

• SOx H2SO4 (sulfuric acid)

• NOx HNO3 (nitric acid)

• long-range transport• pH < 5.6• both precipitation and dry deposition

Major Sources of SO2 Emitters

pH scale

Acid rain effects

Bondville, IL

Acadia National Park, Maine

Acid rain effects on aquatic organisms

Acid rain today

• still affecting forests and surface waters

• more of a nitrogen than sulfur problem

• certainly 1990 Clean Air Act helped

Air Pollution: Legislation and Standards

• Clean Air Act of 1970– amendments in 1977 and 1990

• Amendments of 1990– comprehensive regulations enacted by U.S

congress that address acid rain, toxic emissions, ozone depletion and automobile exhaust

– in 1990 more flexibility, market system allows polluters to choose most cost effective methods

• still can’t meet ozone standards

SO2 scrubber

SoyFace at the University of Illinois

SoyFace

• both ozone and CO2

• atmosphere of the future• examine effects on soybean• many scientists involved

Air pollution today

• we have made major improvements– lead, SOx, other gases

• ozone still biggest problem– billions in crop losses

• cars large sources, although each car is now much cleaner