Environmental Science: Air Pollution & Management

Atmosphere

• The atmosphere is a critical system regulating Earth's climate and distributing heat.
• The atmosphere and oceans shape climate, weather and habitability.

Air Environment

• Earth's atmosphere consists of layers with varying temperatures.
• Troposphere: 8-12 km, heated from the Earth's surface, warmest at the bottom, colder with height.
• Stratosphere: heated from the top due to ozone layer absorbing UV radiation.
• Mesosphere: temperature reduces with height.
• Thermosphere: no defined upper limit, high temperature; N2 & O2 absorb solar radiation reaching 1200 °C at 500 km.

Clean Air Composition

• Clean, dry air composition includes 78% nitrogen, 21% oxygen.
• Other gases: argon (0.9%), water vapor (0-3%), carbon dioxide (0.035%), methane (0.00017%), hydrogen (0.00006%), nitrous oxide (0.000033%).
• Also includes carbon monoxide, ozone, ammonia, sulfur dioxide, nitrogen oxides, CFCs, peroxyacetylnitrate, and volatile organic compounds.

Roles of the Atmosphere

• Supplies oxygen for human biological needs: 12 kg/day at rest, 45 kg/day during light work, 69 kg/day during heavy work.
• Acts as a heat and water transport medium via the water cycle and heat transfer.
• Serves as waste disposal medium.
• Filters solar radiation: harmful UV absorbed by O3 & O2.
• Redistributes solar radiation with a natural greenhouse gas effect, maintaining a temperature of 14-15°C.

Factors Affecting Air Pollution

• Emission sources can be natural or man-made, control/management of emissions.
• Meteorological conditions: transport/diffusion affecting air pollution dilution with secondary air pollution.
• Topography affects pollutant dispersion and deposition.

Environmental Kuznets Curve (EKC)

• EKC illustrates the relationship between environmental degradation and income per capita.
• Strong vs weak rule of law enforcement affects the curve's turning point.

Definitions

• Air contaminants are materials other than the normal clean composition of air.
• Air pollutants cause damage and harmful effects.
• Air pollution is the presence of substances in outdoor/indoor air at concentrations and durations causing measurable adverse effects on humans, animals, vegetation, or materials.

Air Pollution Episodes

• High pollutant concentration coinciding with stagnant air in densely populated areas leading to increased illness/mortality from respiratory diseases.
• Examples: London sulfurous smog (SO2, Soot), Los Angeles photochemical smog (NOX, HC, O2), and Indonesian forest fire (fine PM).

Air Pollution Episodes: Examples

• London killer smog (Dec. 1952) is an impact of air pollution, study air pollution to predict episodes.
• Meuse Valley 1930: Pollutants trapped, produced estimated 8 ppm SO2, concentration reached 22,600 ug/m³, 63 deaths.
• Poza Rica de Hidalgo 1950: Hydrogen sulfide vented at an oil field, 22 killed, 320 hospitalized.

Types of Air Pollutants

• By generation source: nature or man-made.
• By aggregation state: gaseous like CO, NOx, SO2, VOC, or PM (solid/liquid suspended in the air).
• PM terminology: TSP, PM10, PM2.5, ultrafine, nanoparticles.

Air Pollutants cont.

• By nature: chemical, biological (pathogens, bacteria, virus, pollens), or physical (noise, EM waves, heat).
• By formation: primary (as emitted) or secondary (formed in atmosphere such as secondary particles and ground level ozone).
• By chemical composition: S-containing, N-containing, etc.
• By potential effects: toxic, hazardous, oxidants, GHGs, ozone depleting substances.
• By regulation: criteria pollutants, non-criteria pollutants.

Common Classification Of Air Pollutants

• Major Air Pollutants: Particulate Matter (PM), Sulphur dioxide (SO2), Nitrogen dioxide (NO2), Carbon monoxide (CO), Lead (Pb) and Ozone (O3)
• Hazardous Air Pollutants: VOCs, semi-VOCs (PAH, PCB, pesticides), heavy metals.

Major Atmospheric Pollutants

• Carbon monoxide (CO): reduces oxygen-carrying capacity of blood, contributes to ozone.
• Carbon dioxide (CO2): from burning fossil fuels, contributes to global warming.
• Nitrogen oxides (NOx): from road transport, contribute to smog and global warming.
• Sulfur dioxide (SO2): from burning fossil fuels, contributes to smog and acid rain.
• Ammonia (NH3): from agriculture, reacts with pollutants to form particulate matter.
• VOCs: from road transport/solvents, contributes to ground-level ozone and smog.
• Ozone (O3): formed from other pollutants, a major component of smog.
• POPs are volatile chemicals persisting in the environment, can have effects on health.
• Particulate matter (PM): causes haze and lung problems.
• Heavy metals: from burning fossil fuels and road transport, some are toxic.

General Classification of Gaseous Pollutants

• Primary air pollutants are directly emitted such as particulates, carbon monoxide and sulfur oxide.
• Secondary air pollutants are formed by chemical reactions; ozone and haze.

Particulate Matter (PM)

• Most important for health effects (mortality and morbidity).
• High levels in developing countries.
• Can be primary or secondary particles.
• Particle size affects health, dispersion, formation, light absorption, and climate.

Fine Particle (PM2.5)

• Particulate Matter with a diameter equal to or less than 2.5 µm is called "fine particle".
• Tiny particles in the air that reduce visibility and cause hazy conditions.

Modes of Ambient Particle Size Distribution

• Different modes in a typical atmospheric particle size distribution exist.
• Size can be equal to either coarse or fine particle, or also primary or secondary PM.

Black Carbon (BC) and Organic Carbon (OC)

• Classification of carbon particles into light-absorbing and refractory categories.

Other Pollutants

• Sulfur Oxides (SO2 and SO3): Major effects as acid precursor, respiratory problems, eye damage, etc.
• Nitrogen oxides (NOx): mixture of nitric oxide (NO) and nitrogen dioxide (NO2), contributes to smog.
• Tropospheric Ozone: formed from precursors, affects lungs, eyes, damages plants and building materials.
• Carbon Monoxide (CO): disrupts oxygen supply when entering the bloodstream, limiting oxygen in blood.

Combustion Sources

• Combustion is a main source of air pollution with varying contributions from power, industry, transport and buildings.

Combustion Air Pollutant Formation

• Burning carbonaceous matter with air results in complete combustion.
• Incomplete combustion emits PICs (CO, soot, HC).
• NOx is formed from nitrogen in air at high temperature.
• Burning non-carbonaceous matter results in air pollution emission.

Manmade Emission

• Emission sources vary by region/country.
• Power plants, transport, and industry are major contributors.

Sources of Pollutants

• Industrial facilities contribute significantly.
• Biomass open burning releases large amounts.
• Household emissions from cooking contribute as well.
• Mobile sources contribute a substantial amount in developing countries.
• Natural sources as well.

Man-made vs Natural Sources

• Man-made sources contributes less than natural sources but cause imbalance of nature.

Global Aerosol Emission Flux

• Natural sources make up the majority of aerosol emissions.
• Anthropogenic sources have a important effect in localized areas.

Measurement Units and Averaging Time

• PM is measured in weight/volume (µg/m³).
• Gases are measured in weight/volume (µg/m³) or volume/volume (ppm, ppb).
• Units are convertible based on temperature, pressure, and molecular weight.

Standard Temperature and Pressure

• STP: Pressure = 1 atmosphere = 760 mmHg, Temperature = 0°C = 273K.
• USEPA standard conditions for ambient air: Pressure = 760 mmHg, Temperature = 25°C = 298K.
• USEPA standard conditions for emission: Pressure = 760 mmHg, Temperature = 20°C = 293K.

General Formula for Unit Conversion

• C[mg/m³] = 10-3 × C[ppm] × MWpol × P/(RuT)
• At 0°C, 1 atm (STP): C[mg/m³] = C[ppm] × MWpol/22.41
• At 25°C, 1 atm (SC): C[mg/Nm³] = C[ppm] × MWpol/24.45

Correction of Gas Volume for Temp and Pressure

• Volume at actual temperature and pressure.
• Volume at reference temperature and pressure.

Temperature Units and Conversion

• Formulas exist for converting between Fahrenheit, Celsius, Kelvin and Rankine.
• Use dimensional analysis/factor-label method

Averaging Time

• Longer averaging/sampling time leads to lower average concentration.
• Time after release affects concentration, greater activity causes shorter time periods, stagnant air affects results.
• Specify "sampling time" of ambient air quality data

Averaging Time of Ambient Air Quality Standard

• Physical processes cause higher concentrations at shorter averaging periods.
• Instantaneous concentration assessments are difficult to measure.
• Exposure assessments are averaged over a period.
• Higher concentrations result from short exposure.
• Long exposures result in lower concentrations.
• Averaging Times: US and Thailand have different PM standards.

Asian and Global Air Pollution Status

• Urban population growth in less and more developed regions.
• Pollutants status and trends in developed and developing countries.
• Air Pollution in Asia: is worsening in urban areas, and has increasing emmisions.