Environmental Science: Air Quality and Pollution

Course Information

• Course Title: Environmental Science and Engineering
• Course Code: EAAC0423
• Department: Mechanical Engineering
• University: Bataan Peninsula State University
• Instructor: Engr. Andrea Shane M. Torres
• Course Level: BSME (3A, 3B, 3C)

Air

• Mostly a gas, but not just gas as it is important to living things
• Air holds water
• Air changes in composition as altitude increases, acting as a protective cushion
• Air pollution measured by Air Quality Index (AQI)

Air Pollutants

• Pervasive throughout areas, occurring from daily life activities such as transportation, power generation, heating, and waste incineration
• Generated by chemical, manufacturing, and agricultural processing
• Pollutant byproducts are often localized in nearby areas but can be spread over long distances by tall stacks and prevailing winds
• Categorized as point sources, area sources, and mobile sources

Air Quality Index (AQI)

• Designed by EPA to report daily levels of ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide
• Ranges from 0 to 500, and corresponding colors represent different health concerns
• 0-50: Good (Green)
• 51-100: Moderate (Yellow)
• 101-150: Unhealthy for sensitive groups (Orange)
• 151-200: Unhealthy (Red)
• 201-300: Very unhealthy (Purple)
• 301-500: Hazardous (Maroon)

Ozone

• Highly reactive gas composed of three oxygen atoms
• Exists naturally in the stratosphere (upper atmosphere) and troposphere (lower atmosphere)
• In the troposphere, the ozone are categorized as an air pollutant
• It readily reacts with other molecules which damages the respiratory systems
• Excessive exposure can increase air intake and allow ozone molecules to penetrate sensitive areas of the lungs and damage them, causing health risks

Why the Ozone Layer is Important

• Absorbs between 97% to 99% of the ultraviolet radiation (UV-B)

Particulate Matter

• "Fine particles" are less than 2.5 microns in size and require electron microscopy for detection
• Formed by the condensation of molecules into solids or liquid droplets
• "Coarse particles" are between 2.5 and 10 microns in diameter and cannot penetrate as readily as fine particles
• Exposures to sulfur dioxide exacerbate the effects of particulate matter
• Diesel fuel can contain up to 500 ppm by weight of sulfur, increasing the harmful effects of ozone when both gases are present

Dioxin

• Group of compounds causing similar adverse health effects
• Classified as chlorinated dibenzo-p-dioxins (CDDs), chlorinated dibenzofurans (CDFs), and polychlorinated biphenyls (PCBs)
• Can be created through combustion of certain materials, chlorine bleaching of pulp and paper, and certain chemical manufacturing processes

Asbestos

• Generic term for silicate materials occurring in fibrous form
• Fibrous form classified as "chrysotile"
• Air concentrations measured in nanograms per cubic meter; background concentrations usually range from 0 to 10 ng/m³

Motor Vehicle Emissions

• Conventional Otto Cycle Engine is a four-stroke, spark-ignited, piston engine, invented around 1880 by Nicholas Otto
• The engine processes follows 4 stages of the cycle: Intake, Compression, Power, and Exhaust

Sample Air to Fuel Ratio

• Complete combustion equations in oxygen and in air are provided for C7H13 (a representation of gasoline).
• The ratio between the air and fuel is calculated to 14.5

Stoichiometric Air to Fuel Ratio

• Calculation of the air-to-fuel ratio needed for complete combustion of gasoline
• Ratio is 14.5

Air Pollution Instrumentation

• Used in monitoring source and ambient air quality
• Categorized as manual monitoring and continuous monitoring
• Subdivisions of manual monitoring: Manual monitoring-source instrumentation;
• Subdivisions of continuous monitoring: Opacity monitors; Gaseous emission monitors; Extractive monitors

Continuous Monitoring-Source Instrumentation

• Two basic types of source emission monitoring instrumentation:
  • Opacity monitors (Transmissometers)
  • Gaseous emission monitors
• Two basic types for opacity monitors:
  • Single-pass systems
  • Double-pass systems
• Two basic types for gaseous emission monitors:
  • In-situ systems
  • Extractive systems

Extractive Monitors

• Withdraw a gas sample for analysis
• Three general categories:
  • Absorption spectrometers
  • Luminescence analyzers
  • Electroanalytical monitors

Indoor Air Quality (IAQ)

• Air quality within and around buildings
• Occurs from different mechanisms:
  • Infiltration
  • Natural Ventilation
  • Forced Ventilation

Infiltration

• Driven by pressure differences between inside and outside of the building
• Influenced by wind and temperature differences
• Can be influenced by openings in the walls, floors, and ceilings
• Infiltration rates expressed in cubic feet per minute (cfm) or air changes per hour (ach)
• Continuous plastic sheet vapor barriers can minimize rates
• Heat-recovery ventilators (HRVs) reduce pollution by transferring heat from outgoing air to incoming air

An Indoor Air Quality Model

• The simple one-box model of a building is considered
• Sources of pollution within the building are characterized by emission rates
• Air entering the building from outside will bring additional pollutants
• Pollutants can be removed by infiltration, ventilation, or a mechanical air-cleaning system.