Air and Air Pollution Notes

Air and Air Pollution

Learning Objectives

  • Review the layers of the atmosphere.

Atmosphere

  • Greek origin: "atmos" (vapor/steam), "sphaira" (ball/globe).
  • Modern Latin: "atmosphaera".
  • Gaseous envelope surrounding the Earth.
  • The total mass of the atmosphere is about 5.3 \times 10^{18} kg.
  • Water is excluded due to its variable concentration.

Layers of Atmosphere

  • Troposphere: Closest to Earth's surface (7-18 km). Most active region for weather. Contains ~80% of air mass and most water vapor. Temperature decreases with altitude. Thinnest layer (10 km).
  • Stratosphere: 19-50 km. Air temperature increases with altitude due to exothermic reactions from UV radiation, producing ozone (O3). Ozone prevents harmful UV rays from reaching Earth's surface.
  • Mesosphere: 30-50 km. Low concentration of ozone and other gases. Temperature decreases with altitude.
  • Thermosphere (Ionosphere): 50-400 km. Temperature increases with altitude due to bombardment by energetic particles from the sun. Ionized particles reflect radio waves.
  • Exosphere: ~400 km. Outermost layer, separating atmosphere from space (~10,000 km thick). Contains spread-out hydrogen and helium. Very cold with no breathable air.

Atmospheric Pressure

  • Pressure at sea level = 1,000 millibars.

Aurora Borealis/Australis

  • Celestial light shows due to ejection of electrons and protons during solar flares.
  • These particles collide with molecules/atoms in the upper atmosphere, causing ionization and electronic excitation.
  • Aurora borealis - Northern Hemisphere
  • Aurora australis - Southern Hemisphere
  • e^- + p^+ + O \rightarrow O^* + e^- + N2 \rightarrow N2^* + p^+ + e^-
  • Excited molecules/ions return to ground state, emitting light.
  • Excited oxygen emits photons at 558 nm (green) and 630-636 nm (red).
  • Blue/violet colors from ionized nitrogen molecule transitions (391-470 nm).

Ecosystem Services of the Atmosphere

  • Protects Earth from most radiation (X-rays, cosmic rays, UV).
  • Ozone (O3) in the stratosphere prevents UV radiation from reaching Earth's surface.
  • Photodissociation of molecular oxygen: O_2 \rightarrow O + O (UV < 240 nm).
  • Reactive O combines with O2 to form ozone: O + O2 + M \rightarrow O3 + M (M = inert substance, N2).
  • Ozone absorbs UV light: O3 \rightarrow O + O2 (UV).
  • Naturally occurring greenhouse gases absorb some reradiated heat.
  • Keeps surface temperature within habitable range for life.
  • Trapping of heat near Earth's surface by gases, particularly CO_2.

Atmosphere and Living Organisms

  • Photosynthesis contributes O2, cellular respiration contributes CO2.
  • Plants use CO_2 to make food.

Air Pollution

Learning Objectives

  • Identify types, sources, and effects of air pollutants.

Definition

  • Presence of chemicals in the atmosphere at concentrations high enough to harm organisms, ecosystems, or human-made materials, or to alter climate.

Types of Air Pollutants

  • Primary: Chemicals emitted directly into the air from a source (natural/human) at harmful concentrations.
  • Secondary: Harmful substance formed when a primary pollutant reacts with substances normally found in the atmosphere or with other air pollutants.

Natural Sources

  • Wind-blown dust, pollutants from wildfires and volcanic eruptions, volatile organic chemicals from plants.
  • Spread out over the globe and removed by chemical cycles, precipitation, and gravity.
  • Some chemicals from volcanic eruptions or forest fires can temporarily reach harmful levels.

Human (Anthropogenic) Sources

  • Combustion of fossil fuels and industrial by-products.
  • Mobile sources: cars, buses, planes, trucks, and trains.
  • Stationary sources: power plants, oil refineries, industrial facilities, and factories.
  • Transportation (57%), industrial processes (12%), fuel combustion (21%), miscellaneous (10%).

Outdoor Pollution

  • Refers to exposures that occur outside of the built environment.

Ozone (O3)

  • Sharp odor detected around electric motors or welding equipment.
  • Found in troposphere and stratosphere.
  • In troposphere, it's a major part of smog.
  • In stratosphere, it's a protective layer against UV radiation (ozone layer).
  • Formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) combine chemically with oxygen in sunlight.

Carbon Monoxide (CO)

  • "The silent killer" – no color, taste, nor smell.
  • When inhaled, it interferes with hemoglobin's ability to carry oxygen.
  • Released when engines burn fossil fuels (automobile exhaust, charcoal fires, propane pumping stoves).

Carbon Dioxide (CO2)

  • Colorless, odorless, tasteless gas.
  • Greenhouse gas.
  • Major sources: 93% from natural carbon cycle; human activities (burning fossil fuels, clearing forests).

Nitrogen Oxides (NOx)

  • Binary compound of nitrogen and oxygen.
  • NO: nitric oxide
  • NO_2: nitrogen dioxide
  • N_2O: nitrous oxide
  • N_4O: nitrosylazide
  • Formed when N in fuel is burned or when N in air reacts with O at high temperature (vehicle engines, coal-fired power plants).
Nitrogen Monoxide (NO)
  • Common name: nitric oxide.
  • A colorless gas
Nitrogen Dioxide (NO2)
  • Reddish-brown gas from burning fossil fuels.
  • Strong smell at high levels.
  • Primary visible component of urban smog.
  • Can react to form ozone, acid rain, or particles.
  • Can combine with moist tissue in lungs to produce an acid.
Dinitrogen Monoxide (N2O)
  • Common name: nitrous oxide.
  • Greenhouse gas emitted from fertilizers, animal wastes, and burning fossil fuels.
  • Largest cause of ozone layer depletion.

Sulfur Oxides (SOx)

  • Binary compound of sulfur and oxygen.
  • SO: sulfur monoxide
  • SO_2: sulfur dioxide
  • SO_3: sulfur trioxide
  • S_2O: disulfur monoxide
  • S2O2: disulfur dioxide
  • Lower sulfur oxides (S7O2, S6O2)
  • Higher sulfur oxides (SO3, SO4)
Sulfur Dioxide (SO2)
  • Corrosive gas. "Rotten egg" smell at high levels.
  • Mostly from burning coal/petroleum in power plants; also from factories.
  • Reacts to form acid rain.
  • Can affect people with asthma/emphysema.
  • Irritates eyes, noses, and throats.
  • Can harm trees and crops, and damage buildings.
Sulfur Trioxide (SO3)
  • Secondary air pollutant formed when SO_2 reacts with oxygen.
  • Reacts with water to form sulfuric acid.

Particulate Matter (PM)

  • Solid or liquid matter suspended in the air. Particles must be < 0.1 mm wide.
  • Divided into coarse and fine particles.
  • Coarse particles: road dust, sea spray, construction.
  • Fine particles: burning fuels in power plants and automobiles.
  • Can enter the lungs - asthma attacks, respiratory problems, premature death.
  • Reduces visibility and corrodes metals.
PM10
  • Particles with an average diameter of 10 μm (1.0 \times 10^4 nm).
  • Length on the order of 4 \times 10^{-4} inches.
PM2.5
  • Subset of PM10 with average diameter ≤ 2.5 μm (2.5 \times 10^3 um).
  • Sources: 62% natural (dust, wildfires, sea salt); 38% human (coal-burning plants, motor vehicles, road constructions).

Lead

  • Blue-gray metal, very toxic.
  • From cars (leaded gasoline), power plants, and other industrial sources.
  • Lead paint and old pipes.
  • High amounts can be dangerous, especially for small children (lower IQ, kidney problems).
  • In adults, increased chances of heart attack and/or stroke.

Toxic Air Pollutants (TAPs) or Hazardous Air Pollutants (HAPs)

  • Come from chemical plants or are emitted when fossil fuels are burned.
  • Chlorine, formaldehyde, arsenic, asbestos, benzene, and dioxin.
  • Asbestos and formaldehyde can be found in building materials and can lead to indoor air problems.
  • Some can cause cancer, birth defects (teratogenic), skin & eye irritation, and breathing problems.
Asbestos
  • Can cause mesothelioma, lung cancer, laryngeal, and ovarian cancer.
  • Can also cause asbestosis (fibrosis of the lungs).
  • Was used for wall insulation, mixed with plastic, sealed into floors, and built into cars.
  • Resistant to heat and corrosion.
Dioxins
  • Persistent organic pollutants (POPs).
  • More than 90% of human exposure is through food (meat, dairy, fish, shellfish).
  • Found throughout the world and accumulate in the food chain.
  • Highly toxic and can cause reproductive/developmental problems, damage the immune system, interfere with hormones, and may cause cancer.
  • Burning of municipal, hospital waste, backyard burning, and automobile emissions contribute to release.

Stratospheric Ozone Depleters

  • Chemicals that can destroy ozone in the atmosphere.
  • Include chlorofluorocarbons (CFCs e.g. CFCl3, CF2Cl2, C2F3Cl3), hydrochlorofluorocarbons (HCFCs), halons, and other compounds containing Cl or Br.
  • CFCs are used in air conditioners & refrigerators as coolants, aerosol cans and fire extinguishers
  • Other ozone depleters are used as solvents in industry.

Volatile Organic Compounds (VOCs)

  • Diverse group of organic compounds emitted as gases from certain solids or liquids.
  • Concentration often higher indoors (>10x) than outdoors.
  • Variety of health effects, depending on the individual chemical.
  • Many are respiratory tract irritants and carcinogenic.
  • Most contribute to photochemical smog.
  • Sources: paints, paint strippers, wood preservatives, aerosol sprays, cleansers, disinfectants, moth repellents, air fresheners, stored fuel, automotive products, hobby supplies, dry-cleaned clothing, pesticide, building materials, furnishings, office equipment, graphics, and craft materials.
  • Health effects: eye, nose, and throat irritation; headaches, loss of coordination, and nausea; damage to kidney, liver, and central nervous system (CNS); some may cause cancer.

Pollens

  • Pollen from trees, weeds, and grass can cause allergies and hay fever.
  • Pollen pollution is expected to increase with global warming.

Molds

  • Mold is a problem affecting indoor air quality.
  • Some molds produce toxins that bring on allergies and asthma.
  • Molds occur in damp buildings or those with high humidity.

Industrial Smog

  • Air pollution in an urban area is referred to as smog or industrial smog.
  • Industrial smog is generally worse during the winter months.
  • Smog is composed of sulfur oxides and particulate matter.
  • Industrial smog is significant problem in developing countries due to the lack of pollution-control laws.

Photochemical Smog

  • A brownish-orange haze formed by chemical reactions involving sunlight, nitrogen oxide, and hydrocarbons.
  • Photochemical smog was first noted in Los Angeles in the 1940s - Worse in the summer months.
  • Ozone is a principal component of photochemical smog.
  • Results in eye irritation, aggravates respiratory illness, and harms plant tissue.
  • Sources include car exhaust, dry cleaners, and bakeries.
  • Photochemical reaction – any chemical reaction activated by light
  • Primary pollutants: NO, CO and unburned hydrocarbons
  • Secondary pollutants: NO2 and O3
  • N2 (g) + O2 (g) \rightarrow 2NO (g)
  • 2NO (g) + O2 (g) \rightarrow 2NO2 (g)
  • NO_2 (g) + h \nu \rightarrow NO(g) + O(g)
  • O(g) + O2(g) + M \rightarrow O3(g) + M
  • lachrymator – tear producer and causes breathing difficulties

Catalytic Converter

  • A unit that fits into the front part of exhaust system of a vehicle, close to the engine, to reduce the emission of gaseous pollutants, such as carbon monoxide (CO), nitrogen oxides (NOx) and hydrocarbons (HCs).

Acid Rain

  • Sulfur dioxide and nitric oxide emissions react with water vapor in the atmosphere to form acids that return to the surface as either dry or wet deposition.
  • Wet deposition - includes sulfuric acid and nitric acid in precipitation
  • Dry deposition – dry particles of sulfuric acid and nitric acid that settle out of the air
  • Acid rain usually has a pH between 4.2 and 4.4
  • Can corrode limestone and marble (CaCO_3)
  • 2CaCO3 (s) + 2SO2 (g) + O2 (g) \rightarrow 2CaSO4 (s) + CO_2 (g)
  • CaCO3 (s) + H2SO4 (aq) \rightarrow CaSO4 (s) + H2O (l) + CO2 (g)
  • Harmful effects: damages statues and buildings, contributes to human respiratory diseases, leach toxic metals from soils and rocks into lakes, harms aquatic ecosystems and affects forests.
  • liming – a process of adding quicklime (CaO) to lakes and soils to reduce their acidity

Ozone Depletion

  • Stratospheric Ozone Thinning is the accelerated destruction of ozone in the stratosphere by human-produced chlorine and bromine containing chemicals.
  • ozone hole – a region of exceptionally depleted ozone in the stratosphere over the Antarctic
  • CFCl3 \xrightarrow{UV} CFCl2 + Cl
  • CF2Cl2 \xrightarrow{UV} CF_2Cl + Cl
  • Cl + O3 \rightarrow ClO + O2
  • ClO + O \rightarrow Cl + O_2
  • O3 + O \rightarrow 2O2
  • ChloroFluorocarbons (CFCs):
  • CFC-12 (CF2Cl2) – used as coolant and refrigerant
  • CFC-11 (CFCl_3) – used to blow holes in soft plastics
  • CFC-13 (CF2Cl - CFCl2) – cleaning circuit boards
  • Harmful effects: exposure to UV radiation increases the risk of skin cancer and genetic mutations, linked to ocular cataracts and weakened immunity, damage ecosystems, crops, materials and finishes.

Montreal Protocol

  • A global agreement to protect the stratospheric ozone layer by phasing out the production and consumption of ozone-depleting substances (ODS). It was finalized in 1987 in Montreal, Canada.
  • The protocol sets limits on the production of chlorofluorocarbons (CFCs), halons and related substances that release chlorine or bromine to the ozone layer of the atmosphere.

Effects of Air Pollutants

  • Injures organisms, reduces visibility, corrodes materials, harms the respiratory tract, reduces crop productivity and involved in acid deposition, global warming, and stratospheric ozone depletion

Ozone (O3) Health Effects

  • Irritates eyes and respiratory tract, produces chest discomfort, Aggravates respiratory conditions such as asthma and chronic bronchitis and Can lead to sore throat, cough, breathing difficulty
  • Environmental Effects: Reduces air visibility, Stresses plants and reduces their vigor, chronic ozone exposure lowers crop yields, forest decline and greenhouse gas associated with global climate change.

Carbon Monoxide (CO) Health Effects

  • Reduces the amount of oxygen reaching the body’s organs and tissues, Acute exposure: dizziness, headache, decreased physical performance, vomiting, nausea and death and chronic exposure: stress on cardiovascular system, fatigue at low levels, heart attack and mental impairment due to high exposure levels (CO poisoning)
  • Environmental Effects: contributes to climate change and global warming.

Nitrogen Oxides(NOx) Health Effects

  • Acute exposure: lung irritation, chronic exposure: bronchitis, affect the senses and cause cough, shortness of breath, respiratory infections, and aggravate asthma
  • Environmental Effects: Damage to vegetation (including leaf damage, decreasing growth) involved in the production of photochemical smog, contribute to acid rain, are associated with global warming and ozone depletion and reduces visibility

Sulfur Oxides (SOx) Health Effects

  • Difficulty in breathing, inflammation of respiratory tract (acute exposure), aggravation of asthma (acute exposure) and Emphysema and bronchitis (chronic exposure)
  • Environmental Effects: Main contributor to acid rain, Harm Plants, crops, soils and aquatic life (decreased growth to plants)

Particular Matter (PM) Health Effects

  • Increased respiratory symptoms and heart disease, irregular heartbeat, reduced lung function, tightness of the chest.
  • Environmental Effects : Contributes to acid rain and poor visibility.

Lead (Pb) Health Effects

  • Damages the nervous system, IQ loss and high blood pressure.
  • Environmental Effects: Disturb body functions of phytoplankton and damages internal organs of animals ( break of food chain).

Respiratory System Protection From Air Pollutants:

  • Hair and Cilia that expels contaminated air
  • Effect of prolonged exposure to air pollutants and tobacco smoke leads to lung cancer, asthma attack, heart attack, and stroke.

Natural Factors That Help Reduce Outdoor Air Pollution

  • Settling of particles due to gravity and chemical reactions

Factors Increasing Air Pollution

  • Urban buildings slow wind speed
  • Hills and mountains reduce flow of air in valleys
  • High temperatures promote chemical reactions
  • Emissions of VOCs from certain trees and plants promote formation of photochemical smog

Grasshopper Effect

  • occurs when air pollutants are transported at high altitudes by evaporation and winds from tropical and temperate areas through the atmosphere to the earth’s polar areas. It explains why pilots have reported seeing dense layers of reddish-brown haze over the Arctic
  • Global distillation – the process whereby volatile chemicals evaporate from land as far away as the tropics and are carried by air currents to higher latitudes, where they condense and fall to the ground

Temperature Inversion

  • Under certain atmospheric conditions, however, a layer of warm air can temporarily lie atop a layer of cooler air nearer the ground, creating a temperature inversion. Traps air pollutants on the ground level and allows their concentrations to increase.

Urban Heat Islands

  • Heat from sunlight heated streets, rooftops, and parking lots, radiates into the atmosphere at night. They cause higher concentrations of particulate matter called dust domes and can affect local air currents and weather conditions.

Indoor Air Pollution

  • At least 2.4 million premature deaths per year world-wide and are mostly in Asia. This refers to the air quality within and around buildings and structures.
  • Indoor air pollution can lead to serious health problems, in developed countries, its mostly radon and cigarette smoke.
  • Health effects include respiratory aggravators and potential carcinogen

Fact About Indoor Air Pollution from EPA

  • Levels of 11 common pollutants generally are 2 to 5 times higher inside homes and buildings than they are outdoors, and as much as 100 times higher in some cases and pollution levels inside cars in traffic-clogged urban areas can be up to 18 times higher than outside levels.

Radon (Rn)

  • naturally occurring, colorless, tasteless, odorless, radioactive gas the comes out of the ground all around and below us and can get into any type of buildings, homes, offices, schools, and result in high indoor radon levels.

Solutions to Reduce Threats of Air Pollution

  • Technology exists to control all of the forms of air pollution discussed here
  • Philippine Clean Air Act of 1999 provides the policy framework for the country’s air quality management program

Emission Trading

  • Enables most polluting coal-burning power plants to buy and sell SO! pollution rights and is based largely on self-reporting of emissions

Ways to Reduce Outdoor Air Pollution

  • Burn low- sulfur coal
  • Remove sulfur from coal
  • shift to less polluting sources energy

Ways to Prevent Air Pollution

  • Use less polluting fuels

Ways to Reduce Indoor Air Pollution

  • Circulate a building's air through rooftop greenhouses
  • Prevent radon infiltration
What Can You Do?
  • Remove your shoes before entering your house to reduce inputs of dust, lead, and pesticides

Ways to Prevent Outdoor and Indoor Air Pollution

  • Improve energy efficiency
  • Reduce poverty
  • Transfer energy efficiency and prevention technologies to developing countries

Analyzing Air Pollutants: Air Quality Index (AQI)

  • An index determined by calculating the degree of pollution in the city or at the monitoring point and includes five main pollutants:
  • AQI unit: (ug/m3)
    • Particulate matter
    • Ground level ozone (O3)
    • Sulfur dioxide (SO2)
    • Carbon monoxide (CO)
    • Nitrogen dioxide (NO2)