Environmental Engineering - Atmosphere and Air Pollution Notes

Atmosphere

  • The atmosphere is very thin compared to the size of the Earth.
  • It has a surface but no clear top, gradually thinning with altitude.

Layers of the Atmosphere

  • Troposphere:
    • Experiences convection, leading to weather.
    • Temperature decreases with increasing altitude.
  • Stratosphere:
    • Temperature increases with increasing altitude.
  • Mesosphere:
    • Temperature decreases with increasing altitude.
    • No ozone layer present.
    • Low air density.
  • Thermosphere:
    • Temperature increases with increasing altitude.
    • Location of the International Space Station (ISS) and space shuttle.
    • Experiences extreme temperatures but low heat due to low air density.
    • Aurora occurs here.
  • Exosphere

Vertical Temperature Profile

  • Shows temperature variations across different altitudes.
  • Includes boundaries like the tropopause, stratopause, and mesopause.
  • Thermopause boundary

Atmospheric Composition (by Volume)

  • Nitrogen: 78.09 \%
  • Oxygen: 20.94 \%
  • Argon: 0.93 \%
  • Carbon Dioxide: 0.0318 \%
  • Neon: 0.0018 \%
  • Helium: 0.00052 \%
  • Krypton: 0.0001 \%
  • Xenon: 0.000008 \%
  • Nitrous Oxide: 0.000025 \%
  • Hydrogen: 0.00005 \%
  • Methane: 0.00015 \%
  • Nitrogen Dioxide: 0.0000001 \%
  • Ozone: 0.000002 \%
  • Sulfur Dioxide: 0.00000002 \%
  • Carbon Monoxide: 0.00001 \%
  • Ammonia: 0.000001 \%

Other Atmospheric Details

  • Meteors are observed in certain layers.
  • The ozone layer blocks UV rays.

Air Circulation and Weather

  • Convection process:
    • Air molecules absorb heat from the Earth.
    • Air expands and rises.
    • Releases heat at the top.
    • Cools and is pulled back to the ground by gravity.
    • This process primarily occurs in the troposphere.
  • Weather patterns in the Philippines:
    • Northeast monsoon (Amihan).
    • Southwest monsoon (Habagat).
    • Intertropical convergence zone where trade winds intersect.
  • "Leap-frogging" deposition at high altitudes.

Air Pollution

  • Defined as any alteration of physical, chemical, and biological properties of the atmosphere that can be harmful (RA 8749).

Sources of Air Pollution

  • Man-Made:
    • Motor vehicles.
    • Industry.
    • Power plants.
    • Agricultural sprays.
    • Solid waste disposal.
  • Natural:
    • Plant and tree pollens.
    • Bacteria and spores.
    • Gases and dust from fires.
    • Fogs.
    • Ozone & nitrogen dioxide from lightning.
    • Volcanic ash and gases.
  • Stationary Sources:
    • Buildings or immobile structures emitting pollutants (RA 8749).
    • Point sources (e.g., industrial plants).
    • Area sources (e.g., construction sites).
  • Mobile Sources:
    • Vehicles using combustion of fuel for conveyance (RA 8749).
  • Biogenic sources: plants and animals

Air Pollutants

  • Any substance in the atmosphere, other than natural components, that is detrimental to health or the environment.

Types of Pollutants

  • Primary Pollutants:
    • Emitted directly into the atmosphere (e.g., sulfur dioxide, nitrogen dioxide).
  • Secondary Pollutants:
    • Formed by atmospheric reactions (e.g., photochemical smog).

Major Air Pollutants

Particulate Matter (PM)

  • Primary source: combustion.
  • Smaller size is more dangerous.
  • TSP (Total Suspended Particulate) measures particulate matter concentration.
  • Primary Particles: originate from construction, agriculture, fires, smokestacks
  • Secondary Particles: from power plants, industrial activities and vehicles.
  • Dusts:
    • Solid particles entrained by process gases.
    • Direct products of mechanical operations.
  • Fumes:
    • Solid particle formed by condensation of vapors (size: 0.03 to 0.3 micrometer).
  • Mists:
    • Entrained liquid particles formed by condensation or chemical reaction (size: 0.5 to 3.0 micrometer).
  • Smoke:
    • Solid particles from incomplete combustion (size: 0.05 to 1 micrometer).
  • Sprays:
    • Liquid particles from atomization of a parent liquid.

Nitrogen Oxides (NOx)

  • Precursors to smog and acid rain.
  • Formed when fuel is burned at high temperatures.
  • Major sources: transportation and stationary fuel combustion.
  • Nitrogen Monoxide (NO):
    • Produced when air is heated to high temperatures.
  • Nitrogen Dioxide (NO2):
    • Brownish, reactive gas in urban atmospheres.
    • Can irritate lungs and lower resistance to respiratory infections.
    • Formed by the oxidation of nitric oxide (NO).

Sulfur Oxides (SOx)

  • Sulfur Dioxide (SO2):
    • Colorless, toxic gas irritating to the respiratory system.
    • Affects breathing and aggravates respiratory and cardiovascular diseases.
    • Contributes to acid deposition, damaging ecosystems and buildings.
    • Combines with water vapor to form sulfuric acid and sulfates.
    • Released from burning coal and oil.
    • Ambient SO2 from stationary sources like coal combustion, steel mills, and refineries.
    • Industry is a major contributor (90\%, transport is 9\%, open burning is 1\%.

Carbon Oxides

  • Carbon Monoxide (CO):
    • Colorless, odorless, poisonous gas from incomplete burning of carbon in fuels.
    • Reduces oxygen delivery in the bloodstream.
    • Threatens those with cardiovascular disease.
    • Impairs visual perception, dexterity, and learning ability.
    • Mostly from transportation sources.
  • Carbon Dioxide (CO2):

Hydrocarbons

  • Organic compounds containing only hydrogen and carbon (e.g., methane).
  • Unburned fumes from gas tanks and vehicle exhausts.
  • Related to photochemical smog and greenhouse gases.

Ozone (O3)

  • Stratospheric Ozone:
    • Screens out UV radiation.
    • Destroyed by man-made pollutants (e.g., CFCs).
  • Ground Level (Tropospheric) Ozone:
    • Man-made pollutant in the lower atmosphere.
    • Secondary air pollutant and component of photochemical smog.
    • Photochemical oxidant and major component of smog.
    • Formed through reactions of VOCs and NOx in sunlight.
    • Damages lung tissue and reduces lung function.

Lead (Pb)

  • Exposure through inhalation and ingestion.
  • Excessive exposure causes seizures, mental retardation, and behavioral disorders.
  • Low doses cause central nervous system damage.
  • May contribute to high blood pressure and heart disease.
  • Sources: lead gasoline additives, smelters, and battery plants.

Table of Air Pollutants

  • Particulate Matter: Variable Composition. Primary pollutant. Solid particles.
  • Lead: Pb. Primary pollutant. Solid particles.
  • Sulfuric Acid: H2SO4. Secondary pollutant. Liquid droplets.
  • Nitrogen Dioxide: NO_2. Primary pollutant. Reddish-brown gas.
  • Sulfur Dioxide: SO_2. Primary pollutant. Colorless gas with strong odor.
  • Carbon Monoxide: CO. Primary pollutant. Colorless, odorless gas.
  • Carbon Dioxide: CO_2. Primary pollutant. Colorless, odorless gas.
  • Methane:CH_4.Primary pollutant. Colorless, odorless gas.
  • Benzene:C6H6.Primary pollutant. Liquid with sweet smell.
  • Ozone:O_3.Secondary pollutant. Pale blue gas with acrid odor.
  • Chlorine:Cl_2.Primary pollutant. Yellow-green gas.

Criteria Air Pollutants

  • Affect human health and the environment.
  • EPA uses six criteria pollutants as indicators of air quality:

Nitrogen Dioxide (NO2)

  • Brownish gas that irritates the respiratory system and originates from combustion.

Ozone (O3)

  • Primary constituent of urban smog, formed by the reaction of VOCs and NOx in sunlight.

Carbon Monoxide (CO)

  • Reduces the blood's ability to carry oxygen and is a product of incomplete combustion.

Lead (Pb)

  • Affects the learning abilities of children and is toxic to the liver, kidney, and blood-forming organs.

Particulate Matter (PM10 and PM2.5)

  • Causes respiratory disorders.

Sulfur Dioxide (SO2)

  • Precursor to acid rain, along with NOx, and is formed when fuel containing sulfur is burned.

National Ambient Air Quality Guidelines

  • Established to protect the environment by defining maximum concentration limits for pollutants.

Ambient Air Quality Guideline Values

  • Concentrations of air pollutants over specified periods, serving as goals for health and public welfare protection.
  • Used as a basis for preventing, controlling, or abating health impacts from air pollution.
  • Maximum limits are represented by 98th percentile values.

Ambient Air Quality

  • The general amount of pollution present in a broad area, reflecting the atmosphere's average purity.

Ambient Air Quality Monitoring

  • Measurement of a representative air sample to indicate pollutant concentrations in the atmosphere.

Methods for Sampling and Measurement

  • TSP High Volume-Gravimetric
  • PM10-High Volume with 10 micron particle size inlet; Gravimetric
  • Sulfur Dioxide Gas Bubbler and Pararosaniline Method (West and Gaeke Method), or Flame Photometric Detector
  • Nitrogen Dioxide Gas Bubbler Griess-Saltzman, or Chemiluminescence Method
  • Ozone-Neutral Buffer Potassium Iodide (NBKI), or Chemiluminescence Method
  • Carbon Monoxide-Non-dispersive Infra-red Spectrophotometry (NDIR)
  • Lead High Volume and Atomic Absorption Spectrophotometry

Philippine National Ambient Air Quality Guideline Values vs. World Health Organization (WHO) Guidelines

Criteria Pollutants

  • Particulate matter (PM10)
  • Sulfur dioxide
  • Carbon monoxide
  • Nitrogen dioxide
  • Ozone
  • lead

Non-criteria pollutants

  • Toluene
  • Xylene
  • Benzene
  • Measures meteorological data, including:
    • Wind direction
    • Wind speed
    • Vertical wind speed
    • Temperature
    • Relative humidity
    • Net radiation
    • Barometric pressure
    • Solar radiation
    • UV radiation

Airsheds

  • Areas sharing common weather conditions and air pollution sources.
  • Interim Airsheds:
    • Metro Manila Airshed
    • Davao Airshed
    • Metro Cebu Airshed
    • Cagayan de Oro City, Geothermal Airshed
    • Naga City Airshed
    • BLIST Airshed (Baguio, La Trinidad, Itogon, Sablan, Tuba)
    • Agusan Del Norte Airshed
    • Zamboanga City Airshed

Air Quality Index (AQI)

  • Index for reporting daily air quality and its health effects.
  • Six levels of health concern:
    • "Good": Air quality is satisfactory.
    • "Moderate" (Fair): Air quality is acceptable but may pose a moderate health concern for sensitive individuals.
    • "Unhealthy for Sensitive Groups": At-risk individuals may experience health effects.
    • "Unhealthy": Everyone may experience adverse health effects.
    • "Very Unhealthy": Triggers a health alert due to more serious health effects.
    • "Hazardous": Triggers health warnings of emergency conditions.
  • Factors considered for AQI:
    • Suspended particulates
    • Sulfur dioxide
    • Photochemical oxidants or ozone
    • Carbon monoxide
    • Nitrogen dioxide

Smog

  • Different smog types:
    • Classical smog/London smog: from burning coal or industrial smog
    • Photochemical smog/Los Angeles smog: from cars and transportation emitting nitrogen oxide
  • Photochemical Smog:
    • Occurs when nitrogen oxides and VOCs react to sunlight, creating a brown haze.
    • Primary pollutants: nitrogen oxides and VOCs from vehicles. Happens in the morning
    • Secondary pollutants: ozone and peroxyacetyl nitrate (PAN).

Smog Formation

  • Morning rush-hour traffic produces nitrogen monoxide (NO):
    • N2 + O2 \rightarrow 2NO
  • NO reacts with oxygen to form nitrogen dioxide (NO2):
    • 2NO + O2 \rightarrow 2NO2
  • NO2 reacts with UV light to form atomic oxygen (O):
    • NO_2 \rightarrow NO + O
  • Atomic oxygen combines with molecular oxygen to form ozone (O3):
    • O2 + O \rightarrow O3

Thermal Inversion

  • Condition where warm air is trapped between two layers of cold air, trapping pollutants.
  • Cool air cannot mix with warm air and pollutants accumulate.

Global Warming

  • Increase in Earth's temperature due to the greenhouse effect of gases.
  • Greenhouse Effect:
    • Warming caused by greenhouse gases, trapping heat.

Climate Change

  • Variation in global or regional climates over time.
  • Attributed to human activity altering the global atmosphere and adding to natural climate variability (UNFCCC definition).

Greenhouse Gases

  • Gases that induce global warming (e.g., carbon dioxide, oxides of nitrogen, chlorofluorocarbons).
  • Carbon Dioxide (CO2):
    • From burning fossil fuels, solid waste, and certain chemical reactions.
  • Methane (CH4):
    • From production and transport of fossil fuels, livestock, and decay of organic waste.
  • Nitrous Oxide (N2O):
    • From agricultural and industrial activities and combustion of fuels.
  • Fluorinated Gases:
    • Synthetic gases from industrial processes.
    • Hydrofluorocarbons
    • Sulfur hexafluoride
    • Perfluorocarbons
    • Nitrogen trifluoride

Kyoto Protocol

  • Protocol to the UNFCCC aimed at fighting global warming.
  • Adopted on December 11, 1997, in Kyoto, Japan, and entered into force on February 16, 2005.
  • First major international agreement towards GHGE reduction.
  • Industrialized countries agreed to reduce emissions of six greenhouse gases to 5.2\% below 1990 levels between 2008-2012.
  • Mechanisms to reduce costs of meeting targets:
    • International Emissions Trading.

Ozone Layer Depletion

  • Ozone is a molecule consisting of three oxygen atoms (O3).
  • Ozone Layer:
    • Located in the stratosphere (20-40 km from Earth's surface).
    • Shields the Earth from harmful UV radiation.
  • 1985: Significant thinning of the ozone layer over Antarctica discovered during the Southern Hemisphere spring.
  • Ozone depletion is also occurring in Arctic regions.
  • Ozone absorbs UV light, splitting into oxygen molecules and atoms:
    • O_2 + O
  • Oxygen molecules split by UV light to form oxygen atoms:
    • O_2 \rightarrow 2O
  • Recombination forms ozone again:
    • O + O + O_2

Ozone Depleting Substances

  • Substances that deplete the ozone layer.
  • Class I:
    • Chlorofluorocarbons (CFCs):
      • Commonly known as "freon."
      • Chlorine reacts with ozone:
        • Cl + O3 \rightarrow ClO + O2
        • ClO + O \rightarrow Cl + O_2
    • Halons
    • Carbon tetrachloride
    • Methyl chloroform
    • Methyl bromide
  • Class II:
    • Hydrochlorofluorocarbons (HCFCs)

Effects of Ozone Depletion

  • Thinning of the ozone layer due to ODS leading to the loss of the blocking effect against UV radiation
  • Allows entry of greater concentrations of UV-B (increased risk of skin cancer, cataracts, suppressed immune system, and damage to plant and aquatic life).

Montreal Protocol (1987)

  • Landmark international accord to address ozone layer damage by synthetic chemicals.
  • Philippines signed on September 14, 1988.

Acid Deposition

  • Accumulation of potential acid-forming particles on a surface.
  • Natural causes: volcanoes, lightning, etc.
  • Man-made causes: burning fossil fuels and use of internal combustion engines.
  • Results when sulfur dioxide (SO2) and oxides of nitrogen (NOx) are converted to sulfuric and nitric acid, respectively, with the reaction of water and oxidizing agents, and return to the surface as either dry or wet deposition.
  • Conversion to acids:
    • sulfuric acid (H2SO4)
    • nitric acid (HNO_3)
    • nitrous acid (HNO_2)

Effects of Acid Deposition

  • Damage to ecosystems causing declining aquatic life and forest decline.
  • Damage to properties (buildings and monuments).

Acid Rain

  • Form of precipitation resulting from acid-forming reactions.
  • Contains high levels of sulfuric or nitric acids.
  • Unpolluted rainwater is slightly acidic due to dissolved carbon dioxide:
    • CO2 + H2O \Rightarrow H2CO3

Indoor Air Pollution

  • Pollutants can be 2-5 times greater than outdoors (according to USEPA).
  • Main concerns:
    • Radon
    • Cigarette smoke
    • Carbon monoxide
    • Nitrogen dioxide
    • Formaldehyde
    • Airborne pesticide residues
    • Lead
    • Asbestos
    • Fungi and bacteria
    • Etc…

Air Pollution Around the World

  • Nine out of 10 people worldwide breathe polluted air (WHO).
  • An "alarming" 7 million people die each year from air pollution.
  • Most pollution-related deaths occur in low- and middle-income countries (Asia and Africa).
  • World's top 5 most polluted megacities based on the number of particles of pollution per cubic meter:
    • Delhi
    • Cairo
    • Dhaka
    • Mumbai
    • Beijing