Air Pollution Chapter 15, Part 1

W HAT IS THE NATURE OF THE ATMOSPHERE ? Section 15-1 PART 1 (thru p. 388)

The earth’s atmosphere is a dynamic system that includes 4 layers T-S-M-T (The Sky Makes Thunder) Know this (O 3 ) – global “sunscreen”

W HAT ARE THE MAJOR AIR POLLUTION PROBLEMS ? Section 15-2

Outdoor air pollutants Some primary air pollutants may react with one another or with other chemicals in the air to form secondary air pollutants. harm organisms, ecosystems, or human made materials, or to alter climate. Natural sources include dust blown by wind, pollutants from wildfires and volcanic eruptions, and volatile organic chemicals released by some plants. Most human inputs come from the burning of fossil fuels in power plants and industrial facilities (stationary sources) and in motor vehicles (mobile sources).

Major Air Pollutants Summary of most of these and others on next slides – review them online. Pollutants with (*) in next slides classified as Nat Amb Air Qual Std - NAAQS criterion pollutants. *Regulated by Clean Air Act * * * * * *

Major Air Pollutants Sulfur dioxide (SO 2 ) * and sulfuric acid: –About one-third of SO 2 in the troposphere occurs naturally through the sulfur cycle. –Two-thirds come from human sources, mostly combustion (S+ O 2 → SO 2 ) of sulfur-containing COAL and from oil refining and smelting of sulfide ores. –SO 2 in the atmosphere leads to INDUSTRIAL SMOG (gray smog) &can be converted to sulfuric acid (H 2 SO 4 ) and sulfate salts (SO 4 2- ) that return to earth as a component of acid deposition –SO2 emissions have seen a sharp decrease with better regulations in developed countries. – Cap & Trade in US *=Nat Amb Air Qual Std criterion pollutant

Major Air Pollutants Nitrogen oxides (NOx) and nitric acid: –Nitric oxide (NO) forms when nitrogen and oxygen gas in air react at the high-combustion temperatures in CAR engines and COAL-burning plants. NO can also form from lightening and certain soil bacteria. NO reacts with air to form NO 2 (nitrogen dioxide) * which reacts to form PHOTOCHEMICAL SMOG. NO 2 reacts with water vapor in the air to form nitric acid (HNO 3 ) and nitrate salts (NO 3 - ) which are components of acid deposition. N 2 O Nitrous Oxide = greenhouse gas from fertilizers, animal waste & fossil fuels

Major Air Pollutants Suspended particulate matter (SPM): –Solid and liquid particles suspended in the air. – 38% from humans –The most harmful forms of SPM* are fine particles (PM-10, with an average diameter < 10 micrometers) and ultrafine particles (PM- 2.5). –According to the EPA, SPM is responsible for about 60,000 premature deaths a year in the U.S.

Major Air Pollutants Carbon oxides: –Carbon monoxide* (CO) is a highly toxic gas that forms during the incomplete combustion of carbon-containing materials—esp. from CARS. –93% of carbon dioxide (CO 2 ) in the troposphere occurs as a result of the carbon cycle. –7% of CO 2 in the troposphere occurs as a result of human activities (mostly burning fossil fuels). It is not regulated as a pollutant under the U.S. Clean Air Act. But the EPA has recognized its accumulation as dangerous.

Major Air Pollutants Lead (Pb): –Lead can be emitted into the atmosphere as particulate matter (PM*) from paint, smelters, and manufacturing. –Accumulates in the body to cause nervous system damage, digestive problems, and cancer –Harms wildlife.

Major Air Pollutants Ozone (O 3 ) *: –Ozone a highly reactive gas that is a major component of photochemical smog. –It can Cause and aggravate respiratory illness. Can aggravate heart disease. Damage plants, rubber in tires, fabrics, and paints. (“good” when in stratosphere)

Major Air Pollutants Volatile organic compounds (VOCs): –Most are hydrocarbons emitted by the leaves of many plants and methane. React with NOx to form PHOTOCHEMICAL SMOG. –About two thirds of global methane emissions comes from human sources. –Other VOCs include industrial solvents such as trichlorethylene (TCE), benzene, and vinyl chloride. Long-term exposure to benzene can cause cancer, blood disorders, and immune system damage.

Major Air Pollutants Radon (Rn): –Radon a naturally occurring radioactive gas found in some types of soil and rock. –It can seep into homes and buildings sitting above such deposits.

Sources of Air Pollution

Smog Industrial smog (“grey”) is a mixture of sulfur dioxide, droplets of sulfuric acid, and a variety of suspended solid particles emitted mostly by burning coal, etc. –rarely a problem in most more-developed countries –China (Bejing below) uses lots of coal → 16 of the world’s 20 most polluted cities.

Smog Photochemical smog (“brown”) is a mixture of air pollutants formed by the reaction of nitrogen oxides and volatile organic hydrocarbons under the influence of sunlight. Mexico City (pictured) and Los Angeles are two of the many cities in sunny, warm, dry climates with many motor vehicles that suffer from photochemical smog.

Decreased outdoor air pollution –Heavy particles settle –Rain and snow help cleanse –Salty sea spray from the oceans washes out many pollutants over the oceans. –Winds sweep pollutants away to mix with cleaner air. –Some pollutants removed by chemical reactions.

Increased outdoor air pollution Factors can increase outdoor air pollution. –Urban buildings, hills, mountains slow wind speed and reduce dilution. Also lead to inversions (below). –High temperatures promote the chemical reactions leading to photoch. smog. –VOCs can be emitted from certain plants. –Grasshopper effect—air pollutants are transported by evaporation and winds to be deposited in earth’s polar areas.

Acid deposition is a serious regional air pollution problem From coal-burning power plants, ore smelters, and other industrial facilities:SO 2 and NO x → sulfuric acid, nitric acid vapor, and particles of acid-forming sulfate and nitrate salts. Descend to the earth’s surface in two forms (often far away if smokestacks): –Wet deposition consisting of acidic rain, snow, fog, and cloud vapor, and dry deposition resulting in a mixture called acid deposition, or acid rain. –Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts). Mixture of wet and dry is called acid deposition— sometimes called acid rain.

Fig. 15-5, p. 381 Wind Transformation to sulfuric acid (H 2 SO 4 ) and nitric acid (HNO 3 ) Windborne ammonia gas and some soil particles partially neutralize acids and form dry sulfate and nitrate salts Wet acid deposition (droplets of H 2 SO 4 and HNO 3 dissolved in rain and snow) Nitric oxide (NO) Sulfur dioxide (SO 2 ) and NO Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts) Acid fog Lakes in deep soil high in limestone are buffered Lakes in shallow soil low in limestone become acidic Acid deposition consists of rain (acid rain), snow, dust, or gas with a pH lower than 5.6. Acid deposition

Current and potential regions where acid deposition is a problem

Acid deposition has a number of harmful effects Damages statues and buildings contributes to disease leaches toxic metals (such as lead and mercury) from soils and rocks into lakes used as sources of drinking water. Toxic metals can accumulate: 45 U.S. states have issued warnings telling people to avoid eating fish caught from waters that are contaminated with toxic mercury. Harms aquatic ecosystems Indirectly kills trees -- leaching essential plant nutrients releasing toxic metals.

Indoor air pollution Major problem where burning of biomass, coal, etc. used for cooking and heat Urban people in MDCs (more devel. countries) and LDCs spend 70–98% of their time indoors/vehicles - 2-5x more pollutants indoors - 18x more pollutants in cars The four most dangerous indoor air pollutants in MDCs are: –tobacco smoke –Formaldehyde from building and household products –radioactive radon-222 gas from underground rock deposits –very small (ultrafine) particles

Numerous indoor air pollutants are found in most modern homes

The distribution of premature deaths from air pollution in the United States At least 2.4 million people worldwide die prematurely each year from the effects of air pollution. 150,000 to 350,000 people in the U.S. + cancer, asthma

Physiological protection Sneezing and coughing help

H OW SHOULD WE DEAL WITH AIR POLLUTION ? Section 15-3

Laws and regulations The U.S. Congress passed the Clean Air Acts in 1970, 1977, and SUCCESS! –The federal government established air pollution regulations for key pollutants that are enforced by states and major cities. –For CO, NO2, SO2, Pb, O3, PM Combined emissions of six major pollutants decreased by ~54% between 1980 and CAA included cap and trade program for SOx.

Reduce pollution More cap and trade programs

Reduce pollution

Prevention