Atmosphere and Air Pollution

• Dr. Sailesh Narayan Behera of the Civil Engineering Department is the instructor for the course.
• The module covers introduction to atmosphere and air pollution, four spheres of Earth and the overview of the Earth's atmosphere.
• The module also covers thickness of Earth's atmosphere, the vertical structure of atmosphere, temperature and pressure, and layers of atmosphere.
• Definition of air pollution, systems of air pollution, philosophy of air pollution control, classification of air pollutants and sources, air quality management and challenges are also covered.

Four Spheres of Earth

• The four spheres are atmosphere, hydrosphere, lithosphere, and biosphere.
• The atmosphere includes all the air in Earth's system, extending more than 10,000 km above the surface.
• The lithosphere contains the cold, hard, solid land of the planet's crust and semi-solid land underneath, in addition to the liquid land near the planet's center.
• The hydrosphere contains all solid, liquid, and gaseous water, ranging from 10 to 20 kilometers in thickness
• The biosphere includes all living organisms and all organic matter that has not yet decomposed.

Earth's Atmosphere

• Earth’s atmosphere contains gases, creates Earth's pressure, absorbs meteoroids and UV radiation.
• It warms the surface through heat retention, and reduces temperature extremes between day and night, facilitating life and liquid water.
• Relative to the size of the Earth, the atmosphere is extremely thin. 90% of its mass is below 16 km.
• Given Earth's diameter is 12,756 km, the atmosphere thickness is comparable to the skin on an apple.

Layers of the Atmosphere

• From closest to the Earth to the furthest away, the layers of atmosphere are named troposphere, stratosphere, mesosphere, thermosphere and exosphere.
• Troposphere is at 0 to 15 km altitude and hosts life and weather.
• Troposphere temperature decreases with altitude and absorbs long-wave radiation emitted from Earth.
• Top of the troposphere is known as the tropopause.
• Stratosphere resides at 15 to 50 km altitude.
• Stratosphere temperatures increase with altitude as ozone (O3) absorbs UV radiation.
• Top of the stratosphere is known as the stratopause.
• Mesosphere resides at 50 to 90 km altitude.
• Mesosphere temperature decreases with altitude.
• The lowest temperatures in the entire atmosphere are found at the mesopause during summer at high latitudes, 130 K (-226°F) can occur. Top of the mesosphere is known as the mesopause.
• Thermosphere resides at 90 to 500 km altitude.
• The temperature increases with altitude above 90 km, and is constant above 200 km.
• This heating is due to absorption of solar radiation (wavelengths are less than 0.2 microns) by molecular oxygen (O2). The highest temperatures in the atmosphere can be found in the thermosphere, 2000 K can occur.
• Temperature increases to 2000°C, and includes the Ionosphere which creates Auroras and is important for radio waves.
• Pressure for any area is defined by the weight (force) of a vertical column of air over the area.

Air Pollution

• Air pollution constitutes when "presence of any substances, solid, liquid or gas in atmosphere in such a concentration that may tend to be injurious to humans, animals, plants, property or the atmosphere itself".
• Clean atmosphere + external addition = effects of air pollution

Air Pollution Sources

• Sources of outdoor air pollution include power plants, construction and road dust, emissions, biomass burning, brick kilns, transportation, open waste burning, and industries.
• Pollution effects lungs, heart, vessels, endocrine system and brain; and causes global, cardiovascular, and pulmonary mortality.
• Air pollution affects include oxidative stress, aging and pigmentation, decreased lung function and growth, and neurological disorder.

Worsening Air Pollution

• Indoor and outdoor air pollution is linked to 7 million premature deaths worldwide annually.
• Some air pollutants affect climate change and accelerate Arctic warming and glacial melt.
• Air pollution affects rainfall patterns, storm intensities, and regional weather patterns such as the monsoon.
• Haze and dust from air pollution can reduce solar yields by as much as 25%.
• Air pollution reduces global crop yields -- up to 15% for wheat and soy and 5% for maize.

Impacts of Air Pollution

• Short-term effects of air pollution can include headache, nose, throat, eyes inflammation, coughing, and painful breathing.
• Long-term effects can include affect central nervous system (headache, anxiety), cardiovascular and respiratory diseases
• Protecting yourself often includes checking air quality index, using face mask, and keeping windows and doors closed

Air Pollution Systems

• Systems involve emissions and atmospheric processes as sources, and concentrations in air and deposition/loading as receptors.
• The system requires source emissions, transport and resulting ambient levels, human exposure, and health effects.

Philosophy of Air Pollution Control

• Reducing pollutant(s) emission to a point such that no noticeable adverse effects associated with pollutant(s) exist.
• Requires understanding/establishing linkages between sources/ receptors.
• Requires establishing safe air quality levels, using Air quality standards, protecting receptors.

Managing Air Pollution Challenges

• Air pollution is 3-Dimensional and transport medium is beyond control/regulation.
• Impacts includes Instant and Chronic effects, and receptors remediation almost impossible.
• The solution can not be delayed.
• Types of remediation includes Medium, Source and Receptor.

Basic Categories of Air Pollutants

• Major air pollutants can be either criterion or non-criterion.
• Criteria pollutants include PM, SO2, NOx, and CO.
• Non-criteria pollutants include Pb, Asbestos, Vinyl chloride, Mercury, Arsenic, and TOC (Trace Organic Carbon).

Criteria Air Pollutants

• 'Criteria air pollutants' are air pollutants that have been regulated, continuously monitored and are used as indicators of air quality
• The Clean Air Act(CAA) of 1970 identified six common air pollutants or concern and can be separated into carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO₂), ozone (O3), lead (Pb), and particulate matter

Smog Formation

• Smog comes from nitrogen Dioxide, Sunlight, and Water, leading to formation of nitric oxide, hydrocarbons, atomic oxygen.

Ground-level Ozone

• Photochemical oxidants are secondary pollutants formed under the influence of sunlight, which contains nitrogen oxides and hydrocarbons.
• Common photochemical oxidants include nascent oxygen [O], excited molecular oxygen (O2), Peroxy-acetyl nitrate (PAN), Peroxy-propinol nitrate (PPN), Peroxy-butyl nitrate (PBN), nitrogen dioxide (NO₂), hydrogen peroxide (H2O2) and alkyl nitrates.

Particulate Matter

• PM2.5 includes combustion components, organic compounds, metals, e.t.c. with a diameter of less than 2.5 microns. PM10 includes dust, pollen, mould, e.t.c. with a diameter of less than 10 microns.

Hazardous Air Pollutants

• Hazardous air pollutants (also known as air toxics), can cause cancer or other serious health, reproductive, birth defect, environmental and ecological effects.
• The USEPA has identified 187 chemicals as HAPs.
• They are more toxic than criteria pollutants, and may reasonably result in irreversible and serious disease including cancer.
• Common HAPs are benzene, Perchlorethlyene, and methylene chloride.
• Most air toxics (HAPS) originate from human-made sources, including cars, trucks, buses, stationary sources, indoor sources etc.

Classifying Air Pollutants

• Air pollutants can be classified by origin, chemical composition, and state of matter.
• Classification by origin separates the pollution into primary and secondary pollutants.
• Primary pollutants are emitted directly to the atmosphere, for example, sulfur dioxide, nitric oxide, carbon monoxide and hydrocarbons.
• Secondary pollutants occur due to photochemical or hydrolysis / oxidation reactions, for example particulate matter, sulfuric acid, Ozone.
• Organic air pollutants contain carbon and hydrogen; and oxygen, nitrogen, phosphorus, and sulfur such as hydrocarbons, aldehydes, ketones, carboxylic acids, alcohols or amines.
• Inorganic materials found in contaminated atmosphere include CO, CO2, carbonates, sulfur oxide, nitrogen oxide and hydrogen chloride.
• States of matter can include particulate (fumes, smoke) or gaseous pollutants.

Air Quality Management

• Involves measurements, emissions options, cost/benefit analysis and a solution that cleans the air.