Presentation by Julian Aherne, School of Environment, focusing on air pollution.
Course code: ERSC-1010H; Date: November 03, 2025.
Gaussian Plume Model
How to determine concentration of an air pollutant at a location downwind of an emissions point (stack) and within the plume.
Mathematical Model
The formula for concentration is given as:
C(x, y, z) = \frac{Q}{2\pi U H \sigmay \sigmaz} \exp \left( -\frac{1}{2} \frac{y}{\sigmay^2} \right) \exp \left( -\frac{1}{2} \frac{z - H}{\sigmaz^2} \right) + \exp \left( -\frac{1}{2} \frac{z + H}{\sigma_z^2} \right)
Variables:
$C(x, y, z)$: Pollutant concentration in $g/m^3$ as a function of downwind position $(x,y,z)$.
$Q$: Mass emission rate of pollutant in $g/s$.
$H$: Effective stack height in meters.
$
u$: Wind speed at ‘effective’ stack height in $m/s$.
$ auy$, $ auz$: Standard deviations in the $y$ and $z$ directions (m), indicating the spread of the pollutant.
Mass distribution in the cross-wind dimension $(y)$ and vertical dimension $(z)$ including effects of surface reflection.
Importance of Air Quality
99% of the global population breathes polluted air.
Air pollution is a transboundary issue; it knows no borders.
International Focus
International Day of Clean Air for Blue Skies: September 7, 2025, focused on the theme "Racing for Air. Every Breath Matters."
Air pollution is described as the biggest environmental health risk of our time.
Impact of Air Pollution
Exacerbates climate change.
Causes economic losses and reduces agricultural productivity.
Exposure to air pollution can lead to:
Stroke
Heart disease
Lung diseases
Cancer, etc.
FAQ section encourages users to download a clean air guide.
Understanding Air Pollution
Definition
Air pollution is defined as the contamination of the atmosphere (particularly the troposphere) by gaseous, liquid, and solid wastes, primarily from anthropogenic sources, at harmful concentrations that adversely affect:
Human health
Environment
Material degradation
Visibility reduction.
Statistics on Health Impact
Air pollution contributes to 1 in 9 deaths, with approximately 7 million deaths annually due to diseases related to air pollution.
Example mortality rates for various diseases:
Diabetes: 1.55 million deaths
Transportation accidents: 1.28 million
Tuberculosis: 1.18 million
HIV: 0.86 million
Breast cancer: 0.70 million
Malaria: 0.64 million
Prostate cancer: 0.49 million
The sum suggests around 6.70 million deaths linked to air pollution.
Specific Impact on Diseases
Air pollution is responsible for:
43% of deaths from chronic obstructive pulmonary disease (COPD)
24% of deaths from ischemic heart disease
29% of deaths from lung cancer
25% of deaths from stroke.
Life Expectancy
Reduction in life expectancy due to air pollution is profound:
Paris: 6 months decrease
Northern India: 10 years decrease.
Case Study: Ella Kissi-Debrah
Notable case in the UK where air pollution was directly listed as the cause of death for Ella Kissi-Debrah, highlighting the severe implications of air quality.
Measuring Air Pollution
Why Care About Air Pollution?
Understanding the impacts and methods of measuring air pollution is crucial for effective management and mitigation strategies.
Definitions and Measurement Techniques
Fine particles (PM2.5) can significantly penetrate the lower respiratory tract.
Human hair: 50-70 μm in diameter
PM2.5: Particles < 2.5 μm in diameter consisting of combustion particles and organic compounds.
PM10: Particles < 10 μm in diameter including dust and pollen.
Types of Pollutants
Primary pollutants: Formed and emitted directly from sources.
Secondary pollutants: Formed through chemical reactions in the atmosphere.
Monitoring Air Quality
Monitoring Networks
Governments and researchers rely on established networks to monitor concentrations of gases and particles, including wet deposition of pollutants.
Examples of monitoring networks include:
AEROCAN
Brewer/Ozonsonde
CAPMON
CORALNet
GAPS
IADN
NAPS
Multiple sites in Canada.
Techniques Employed
Active sampling: Requires power (e.g., to pump air).
Passive sampling: No power required for air collection; relies on diffusion or deposition.
Measurement of Wet Deposition
Wet deposition includes bulk, wet-only, and snow precipitation chemistry monitored through networks like the Canadian Air and Precipitation Monitoring Network (CAPMON).
Gold Standard Monitoring
Ambient concentration measurement of gases and particles considered as the 'gold standard' for air quality assessment.
Challenges in Monitoring
Despite the effectiveness of continuous samplers, practical issues prevent universal application.
Passive Atmospheric Samplers
Functionality
Passive samplers measure ambient gases in the atmosphere without requiring power, through diffusion.
Various designs and chemical reactions employed for specific gases like ammonia (NH3), ozone (O3), and nitrogen dioxide (NO2).
Impact of Air Pollution on Health and Environment
Bioindicators and Biomonitors
Bioindicators: Qualitatively assess biotic responses to air pollution, indicating potential poor air quality.
Biomonitors: Quantitatively assess pollutant concentration, such as through measurement in moss tissue.
Spider webs have emerged as widely used biomonitors compared to other biological indicators.
Goal of Air Monitoring
The ultimate aim of air monitoring is to protect both the environment and human health effectively.
Causes of Air Pollution
Examining case studies like Delhi, particularly during events like the Hindu festival Diwali, illuminates acute pollution events due to: