Atmospheric Pollutants: Comprehensive Lecture Notes

Course Introduction and Learning Outcomes

• Course Details: These lectures are part of GGES3005 & GGES6009 at the University of Southampton, delivered by Ian Williams, Professor of Applied Environmental Science in the Faculty of Engineering and Physical Sciences.

• Primary Objectives: By the end of this lecture series, students should be able to:

  • Classify various types of air pollutants.

  • Identify, explain, and evaluate the physical and chemical nature, sources, and emissions of atmospheric pollutants.

  • Assess the health and environmental effects of gaseous pollutants and particulate matter.

  • Identify key regulatory processes involved in emissions control and air quality management.

• Supplemental Material: The lectures are intended to supplement specific "chapters" and directed reading assignments.

Classification of Air Pollutants

• Physical State: Major air pollutants typically occur in two forms:

  • Gaseous forms.

  • Particulate matter.

• Primary vs. Secondary Pollutants:

  • Primary Pollutants: These are substances emitted directly into the atmosphere from a source.

  • Secondary Pollutants: These are not emitted directly but are produced via chemical reactions between primary pollutants and normal atmospheric compounds.

• Rationale for Classification:

  • Classification is essential to better understand air pollution dynamics.

  • It assists in devising effective pollution control strategies.

  • Primary Pollutants Dynamics: There is a proportional relationship between emissions and concentrations.

  • Secondary Pollutants Dynamics: There is a complex relationship between emissions and concentrations due to the chemical transformations involved.

Sources of Air Pollutants: Natural

• Natural Sources and Phenomena:

  • Volcanic Eruptions: Release significant quantities of gases and ash.

  • Sand and Dust Storms: Known as "Hwangsa" or "Haboob" (e.g., Ransom Canyon, Texas, 2009).

  • Lightning: Produces nitrogen oxides ($NO_x$).

  • Forest Fires: Large-scale combustion releasing smoke and gases (e.g., Greece forest fires, July 25, 2007).

  • Hydrogen Sulfide ($H_2S$): Released from geysers, hot springs, and biological decay in bogs and marshes.

  • Hydrocarbon Seeps: Natural seeps of hydrocarbons from the earth.

  • Ozone ($O_3$): Found in the lower atmosphere resulting from unstable meteorological conditions.

• The Pollen Calendar: Pollen is an often-overlooked natural pollutant affecting hay fever sufferers. Release periods vary by type:

  • Alder: Jan to April.

  • Hazel: Jan to April.

  • Yew: Feb to April.

  • Elm: Feb to April.

  • Willow: March to May.

  • Poplar: March to May.

  • Birch: April to June (Peak in April/May).

  • Ash: April to May.

  • Plane: May.

  • Oak: May to June.

  • Oil seed rape: May to July.

  • Pine: May to July.

  • Grass: May to Sept (Peak in June/July).

  • Plantain: May to Sept.

  • Lime: June to July.

  • Nettle: June to Sept.

  • Dock: June to Sept.

  • Mugwort: July to Sept.

Sources of Air Pollutants: Anthropogenic

• Combustion of Fossil Fuels: Includes power stations and motor vehicles.

• Industrial Processes: Such as coal mining and solvent use.

• Domestic and Industrial Activities: General emissions from heating and manufacturing.

• Gas Leakage: Leakage from the national distribution network.

• Landfill: Emission of various gases from waste decomposition.

Categories of Sources by Location and Mobility

• Stationary Sources: Relatively fixed locations.

  • Point Sources: Pollutants emitted from one or more controllable sites, such as a factory chimney.

  • Fugitive Sources: Pollutants generated from open areas exposed to wind processes, such as dust from a construction site or dirt road.

  • Area Sources: Well-defined areas containing several individual sources of air pollutants, such as a small community or industrial park.

• Mobile Sources: Pollutants emitted from sources that move from place to place.

  • Transportation: Automobiles, trucks, buses, aircraft, ships, and trains.

  • Recreational Vehicles: Snowmobiles, all-terrain vehicles (ATVs), and jet skis.

  • Small Engines and Tools: Lawnmowers, snowblowers, and diesel generators.

  • Heavy Equipment: Cranes and other large construction machinery.

General Effects and Variability of Air Pollution

• Environmental Impacts:

  • Visual Qualities: Creation of smog and haze.

  • Ecological Damage: Impacts on vegetation, animals, and soil health.

  • Water Quality: Degradation via acid precipitation.

  • Structural Damage: Chemical reactions leading to the soiling and erosion of natural and artificial structures.

  • Human Health: Direct impacts on physiology and mortality.

  • Quality of Life: Reduction of recreational opportunities due to poor air quality.

• Regional and Temporal Variability:

  • In Los Angeles, pollution is primarily from mobile sources.

  • In Ohio and the Great Lakes, pollution is largely from point sources.

  • Seasonality: Summer smog is exacerbated by sunshine; particulate matter is a greater problem in dry months; wildfire and tree-clearing seasons vary.

• Global Transport ("Haze From Afar"):

  • Air quality concerns are not limited to urban centers.

  • Pollution on the North Slope of the Arctic possibly originates from Eastern Europe (EE) and Eurasia.

  • The Jet Stream, blowing West to East approximately $5\text{--}7\,miles$ above the surface, transports these pollutants globally.

Influences of Meteorology and Topography

• Key Determining Factors: Topography and meteorology determine the rate at which pollutants are transported away or converted into harmless compounds.

  • They determine if pollution is a mere nuisance or a major health hazard.

  • Primary effects include damage to green plants and aggravation of chronic diseases, usually via low-level exposure over long periods.

• Atmospheric Inversion: A deviation from the normal thermal lapse rate where air temperature decreases with altitude.

  • Definition: A layer where temperature is steady or increases with altitude (warmer air over cooler air).

  • Limited circulation linked with inversion layers leads to major pollution events.

  • Radiation Inversion: Occurs primarily in summer and autumn when the ground cools quickly at night.

  • Subsidence Inversion: Occurs when cloud cover is associated with stagnant air, preventing vertical mixing.

• Topographic Effects:

  • Cities in valleys or "topographic bowls" (e.g., Los Angeles, Mexico City, Cape Town) are more susceptible to smog.

  • Mountains and inversions act as barriers, preventing wind from transporting pollutants away.

Mathematical Potential for Urban Air Pollution

• Determining Factors:

  1. Rate of emission of pollutants per unit area.

  2. Downwind distance mass of air moves through an urban area.

  3. Average speed of the wind ($u$).

  4. Mixing height ($H$): The elevation to which pollutants can be mixed by naturally moving air in the lower atmosphere.

• Proportionality Laws:

  • Concentration is directly proportional to the emission rate and downwind travel distance.

  • Concentration is inversely proportional to wind speed and mixing height (Stronger wind and higher mixing layers result in lower pollution).

Hydroclimate Whiplash

• Definition: Volatility characterized by sudden, large, or frequent transitions between very dry and very wet conditions.

• Impact: This volatility caused UCLA researchers to predict 2025 Los Angeles wildfires days before their occurrence.

• Global Examples (2016–2023):

  • Pacific Southwest (2022-2023): Dry to wet transition; impacts include wildfire, flooding, landslides.

  • North-Central USA (2020-2021): Wet to dry; impacts include flooding, crop loss, hydropower loss.

  • Northern and Central Europe (2018-2019): Wet to dry; impacts include flooding, extreme heat, crop loss.

  • Iran, Pakistan, and Eastern Arabian Peninsula (2022): Dry to wet; impacts include flooding, landslides.

  • Southern China (2022): Wet to dry; impacts include crop and hydropower loss.

  • Central America (2019-2020): Dry to wet; impacts include human displacement and crop loss.

  • Southeast Australia (2019-2020): Dry to wet; impacts include wildfire and flooding.

• Standardized Precipitation Evapotranspiration Index (SPEI): Used to measure the magnitude of these transitions, ranging from $-4$ (brown/dry) to $4$ (green/wet).

Smog Dynamics and Types

• Terminology: The word "smog" was first used in 1905 to describe a mixture of smoke and fog.

• Photochemical Smog (Los Angeles Type / "Brown Air"):

  • Reaction involves sunlight, nitrogen oxides ($NO_x$), and Volatile Organic Compounds (VOCs).

  • Directly related to automobile use and trapped by inversion layers.

• Sulfurous Smog (London Type / Industrial Smog):

  • Produced by burning coal or oil at large power plants.

• Concentration Trends:

  • $NO$ peaks in the early morning (rush hour).

  • $Ozone$ ($O_3$) peaks around noon/midday when solar radiation is highest.

  • $NO_2$ and Hydrocarbons ($HC$) show specific temporal variations correlated with traffic and solar cycles.

Health Effects and World Health Organization (WHO) Data

• Global Statistics:

  • China was cited as the world's deadliest country for outdoor air pollution by the WHO in 2016.

  • Almost the entire global population ($99\%$) lives in places exceeding WHO air quality guideline limits.

  • Air pollution causes $6.7\,million$ deaths annually.

  • Air pollution kills approximately $13\,people$ every minute.

• Indoor Air Pollution:

  • Causes over $3\,million$ deaths each year.

  • Attributable deaths include: Ischaemic heart disease ($32\%$), Stroke ($23\%$), Lower respiratory infection ($21\%$), Chronic obstructive pulmonary disease ($19\%$), and Lung cancer ($6\%$).

  • Solid Fuels: $1/4$ of the world's population cooks with solid fuels (wood, charcoal, crop waste, kerosene), significantly contributing to indoor risks.

• Synergy in Air Pollution:

  • Synergy: The interaction of two or more substances to produce a combined effect greater than the sum of their separate effects.

  • Example: Heat + Air Pollution + Pollen.

  • Example: Smoke + $SO_2$ in damp conditions (as seen in the London Smog disasters).

Concentration, Exposure, and Dose Definitions

• Concentration: The amount of a specific air pollutant per unit volume of air ($mg\,m^{-3}$ or $ppm$).

  • Physical characteristic of the environment at a specific time and place.

• Exposure: Contact between an airborne contaminant and a surface of the human body (outer like skin, or inner like respiratory tract epithelium).

  • Requires the simultaneous occurrence of the pollutant and the person at the same place and time.

  • Quantitatively described by the duration of contact and the concentration.

• Dose: The amount of pollutant that crosses one of the body's boundaries and reaches the target tissue.

• The Sedentary vs. Active Comparison:

  • Two people in a room with constant pollutant concentration have the same exposure.

  • An active person will have a higher dose because faster and deeper breathing delivers more pollutant to the lung tissues compared to a sedentary person.

Regulatory Framework and Criteria Pollutants

• US EPA and the Clean Air Act: The EPA sets National Ambient Air Quality Standards (NAAQS) for six common "criteria air pollutants":

  1. Ground-level Ozone ($O_3$)

  2. Carbon Monoxide ($CO$)

  3. Sulfur Dioxide ($SO_2$)

  4. Particulate Matter ($PM_{10}$, $PM_{2.5}$)

  5. Lead ($Pb$)

  6. Nitrogen Dioxide ($NO_2$)

• Major Regulated Pollutants Categories:

  • Sulfur Oxides: $SO_2$.

  • Nitrogen Oxides: $NO_x$.

  • Carbon Monoxide: $CO$.

  • Metals: Lead ($Pb$), Cadmium ($Cd$), Zinc ($Zn$).

  • Organic Compounds: Benzene ($C_6H_6$), Poly-aromatic hydrocarbons (PAH).

  • Photochemical Oxidants: Ozone ($O_3$), Peroxyacetyl nitrates (PAN).

  • Particulate Matter: $PM_{10}$, $PM_{2.5}$, $PM_1$, Black smoke (BS), Total suspended particulates (TSP).

Course Introduction and Learning Outcomes

• Course Details: These lectures are part of GGES3005 & GGES6009 at the University of Southampton, delivered by Ian Williams, Professor of Applied Environmental Science in the Faculty of Engineering and Physical Sciences.

• Primary Objectives: By the end of this lecture series, students should be able to:

  • Classify various types of air pollutants.

  • Identify, explain, and evaluate the physical and chemical nature, sources, and emissions of atmospheric pollutants.

  • Assess the health and environmental effects of gaseous pollutants and particulate matter.

  • Identify key regulatory processes involved in emissions control and air quality management.

• Supplemental Material: The lectures are intended to supplement specific "chapters" and directed reading assignments.

Classification of Air Pollutants

• Physical State: Major air pollutants typically occur in two forms:

  • Gaseous forms.

  • Particulate matter.

• Primary vs. Secondary Pollutants:

  • Primary Pollutants: These are substances emitted directly into the atmosphere from a source.

  • Secondary Pollutants: These are not emitted directly but are produced via chemical reactions between primary pollutants and normal atmospheric compounds.

• Rationale for Classification:

  • Classification is essential to better understand air pollution dynamics.

  • It assists in devising effective pollution control strategies.

• Primary Pollutants Dynamics: There is a proportional relationship between emissions and concentrations, often represented by: $C_p = k E$ Where:

  • $C_p$ = concentration of primary pollutants

  • $E$ = emissions of primary pollutants

  • $k$ = a proportionality constant depending on the dispersion conditions.

• Secondary Pollutants Dynamics: There is a complex relationship between emissions and concentrations due to the chemical transformations involved, often described by: $C<em>s = f(C</em>p, T, S)$ Where:

  • $C_s$ = concentration of secondary pollutants

  • $f$ = function representing the dependence on primary pollutant concentration ($C_p$), temperature ($T$), and other species ($S$).

General Effects and Variability of Air Pollution

• Environmental Impacts:

  • Visual Qualities: Creation of smog and haze.

  • Ecological Damage: Impacts on vegetation, animals, and soil health.

  • Water Quality: Degradation via acid precipitation, often quantified by:
    $pH = - ext{log}[ ext{H}^+]$

  • Human Health: Direct impacts on physiology and mortality.

Concentration, Exposure, and Dose Definitions

• Concentration: The amount of a specific air pollutant per unit volume of air ($mg \, m^{-3}$ or $ppm$).

• Dose: The amount of pollutant that crosses one of the body's boundaries and reaches the target tissue, expressed as: $D = C imes A$ Where:

  • $D$ = dose

  • $C$ = concentration of the pollutant

  • $A$ = volume of air inhaled (in $m^3$).

Regulatory Framework and Criteria Pollutants

US EPA and the Clean Air Act: The EPA sets National Ambient Air Quality Standards (NAAQS) for six common "criteria air pollutants":

1. Ground-level Ozone ($O_3$)

2. Carbon Monoxide ($CO$)

3. Sulfur Dioxide ($SO_2$)

4. Particulate Matter ($PM<em>{10}, PM</em>{2.5}$)

5. Lead ($Pb$)

6. Nitrogen Dioxide ($NO_2$)