Air and Noise Pollution Studies

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Air and Noise Pollution Studies

• By Prof. Tao Wang

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Chemical Composition
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Concentration Expressions

• Mixing ratio based on volume-volume ratios

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Concentration Expressions

• Metric unit expressed as mass per unit volume
• microgram per cubic meter (µg/m3)
• milligram per cubic meter (mg/m3)

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Conversion between the two units

• M is molecular weight of the pollutant
• P is pressure (mmHg)
• T is temperature (K) at reference, respectively
• Standard condition 760 mmHg 25 C

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Ideal gas law

• PV nRT
• n m/M
• Where R62.36 (mm Hg-L)/(mol-K)

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The electromagnetic spectrum
Adapted from The Atmosphere, Eighth edition, by
F. Lutgens and Tarbuck, Prentice Hall
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Solar radiation spectra

• Solar radiation at the top and bottom of the
  earths atmosphere (blackbody radiation at
  6000 ºF)
• O2, O3, CO2 and H2O absorbing some portions of
  the radiation
• Radiation concentrated in the visible light
  region (green)

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Thermal radiation from earth
Nighttime thermal emission spectrum of the earth

• Earth radiates at 290 K
• Infrared range centered at 11 µm
• Absorption by CO2 and H2O (greenhouse effect)
• Atmospheric window

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The absorptivity of the atmosphere

• The absorptivity of selected gases of the
  atmosphere and the atmosphere as a whole.
• The atmosphere as a whole is quite transparent to
  solar radiation between 0.3 and 0.7 micrometer,
  which include the band of visible light.
• Most solar radiation falls in this range,
  explaining why a large amount of solar radiation
  penetrates the atmosphere and heats Earths
  surface.
• Also , note that longwave infrared radiation in
  the zone between 8 and 11 micrometers can escape
  the atmosphere most readily.
• This zone is called the atmospheric window.

Adapted from The Atmosphere, Eighth edition, by
F. Lutgens and Tarbuck, Prentice Hall
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Greenhouse gas effect

• The heating of the atmosphere.
• Most of the short-wavelength radiation from the
  Sun passes through the atmosphere and is absorbed
  by Earths land-sea surface.
• This energy is then emitted from the surface as
  longer-wavelength radiation, much of which is
  absorbed by certain gases in the atmosphere.
• Some of the energy absorbed by the atmosphere
  will be reradiated Earthward.
• This so-called greenhouse effect is responsible
  for keeping Earth's surface much warmer than it
  would be otherwise.

Adapted from The Atmosphere, Eighth edition, by
F. Lutgens and Tarbuck, Prentice Hall
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Thermal structure

• Thermosphere
• (90 km)
• Mesosphere
• (50 and
• Stratosphere
• (
• O3 absorbs UV
• Troposphere
• (0-10 km)
• Weather etc

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Atmospheric pollution

• Clear atmosphere becomes polluted when it is
  changed by addition of particles, gases or energy
  forms such as heat, radiation, or noise so that
  the altered atmosphere is less useful to mankind
  or poses some harm because of its impact on
  weather, climate, human health, animals,
  vegetation and materials.

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Natural and Anthropogenic pollution

• Natural Pollution
• Volcanic eruption
• particulate matter, SO2, H2S
• Wild forest fires
• smokes, hydrocarbon, CO, CO2, NOx
• Emission from trees, lightning
• levels of pollutants are normally low
• often far from large population
• transient (short-term)
• Anthropogenic Pollution
• Significant environmental problem because of its
  impact on human health and welfare

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History of air pollution

• Before the industrial revolution
• Smokes from fireplace burning of wood and coal
• The industrial revolution (1700s)
• Smoke and ash from boiler for steam
  engines/turbines home heating fireplaces
• 1900-1925
• Smoke and ash from boilers in electricity power
  generation
• 1925-1950
• First smog pollution in Los Angeles
• 1950-1980
• Smog pollution found in major cities around the
  world

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History of air pollution

• 1980s
• Acid rain, stratospheric O3 depletion,greenhouse
  effect of CO2
• 1990s
• Debate on global climate change-warming by
  greenhouse gases versus cooling by particulate
  matter
• Action to phase out Stratospheric ozone depleting
  materials (e.g., CFCs)
• Major effort in the US to control tropospheric
  ozone pollution

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Pri. versus Sec. pollutants

• Primary the pollutants directly from sources of
  emissions,
• such as NOx, SO2 and CO
• Secondary the pollutants that are manufactured
  in the air,
• such as O3 and H2SO4

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Criteria and non-criteria air pollutant

• Criteria pollutant
• those for which ambient air quality standards
  have been set NO2, SO2, CO, O3, PM10 and Lead
  (Pb)
• Noncriteria pollutant
• those other contaminants designated as toxic or
  hazards (e.g.,benzene) and have been studied in
  industrial hygiene environments

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Scales of air pollution
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Sources and sinks of air pollutants

• Hundreds of air pollutants found in the
  atmosphere
• Only a small number of them identified as being
  at levels significantly enough to pose a treat to
  human health and welfare
• Carbon (C) oxides
• Sulfur (S) compounds
• Nitrogen (N) compounds
• Hydrocarbon (HCs) and their derivatives
• Photochemical oxidants (O3 etc)
• Halogenated hydrocarbon
• Particulate matter
• It is important to know
• the sources,
• atmosphere conversions,
• sinks of these compound.

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Carbon Oxides CO and CO2

• CO
• colorless, odorless, and tasteless, mainly from
  the incomplete burning of fossil fuel and other
  organic matter
• 2C O2 ? 2CO
• (CO is a major air pollutant because of its
  health effects, and is regulated under an ambient
  air quality standard.)
• Sources
• transportation, solid waste disposal,
  agricultural burning, and steel production
  (Natural sources include CH4 and HCs oxidation,
  forest fire, microbial processes in ocean and
  soil.)
• Sinks
• chemical reaction with OH in the air (CO OH ?
  CO2 H) and uptake by microorganisms

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Carbon Oxides CO and CO2

• CO2
• relatively nontoxic but contributes to climate
  warming
• Source
• produced from when organic matter is burned,
  weathered, or biologically decomposed.
• C O2 ? CO2
• combustion of fossil fuels (coal and oil) and
  biomass burning. (CO2 has been increasing in the
  past 50 years due to the large use fossil fuel.
  It is a major greenhouse gas.)
• Sinks
• uptake by plants (photosynthesis) and oceans.

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Relevance to Hong Kong

• CO is not major problem in the outdoor (ambient)
  atmosphere but is of a concern in the indoor
  environments.

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Sulfur compounds SO2 and H2S

• SO2
• colorless with odor
• Source
• mainly from burning of sulfur containing fossil
  fuel such as coal and oil, as well as roasting
  metal sulfide ores in steel and iron industries.
  (Major natural source is volcanoes and oxidation
  of reduced S compounds.) SO2 has important health
  and environmental implications, and is regulated
  under an air quality standard.
• Sinks
• by wet and dry deposition and conversion to H2SO4
  and sulfate (then removed from wet and dry
  deposition)
• SO2 OH ? HOSO2
• HOSO2 O2 ? HO2 SO3
• SO3 H2O ? H2SO4

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Sulfur compounds SO2 and H2S

• H2S (hydrogen sulfide)
• It is very toxic with rotten egg odor, but its
  concentration is normally low in non-industrial
  regions.
• Source
• oil and gas extraction, petroleum refinery, paper
  mill etc. (Natural emission is mainly from
  anaerabic decomposition processes.)
• Sink
• Atmospheric conversion to SO2. (This has
  implication to atmospheric chemistry.)
• The major air quality concern of H2S is malodor
  and discolorization of lead-based paints.

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Nitrogen compounds

• N2, N2O, NO, NO2, NO3, N2O5, HNO3, HNO2,
  CH3COO2NO2, NO3, HCN, NO3-, NO2-, NH4-
• Nitrous Oxide(N2O) colorless, nontoxic, slightly
  sweet, relatively non-toxic (widely used as an
  anesthetic)
• produced naturally from soils by anaerobic
  bacteria. It can dessociate by short UV in the
  stratosphere to produce NO, thus can influence
  ozone in the stratosphere.

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Nitrogen compounds

• Nitric Oxide (NO)
• colorless, odorless, tasteless, and relatively
  nontoxic important in smog chemistry
• Source
• high temperature combustion from automobile
  exhaust and stationary sources such as power
  plants (Major natural source is anaerobic
  biological processes in soil and water.)
• N2O2 ? 2NO
• Nitrogen Dioxide (NO2) colored as light
  yellowish at low concentrations to reddish at
  high concentrations, it is toxic and corrosive
  gas. (NO and NO2 play important roles in smog
  pollution and climate change.)

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Nitrogen compounds

• NO2 source
• atmospheric oxidation of NO
• 2NO O2 ? 2NO2 (slow at low NO level)
• NO O3 ? NO2 (major path)
• Under sunlight
• NO2 hv ? NO O
• OO2 ? O3
• Rapid conversion between NO and NO2 via above
  reaction NOx NONO2
• Sink of NOx NO ? NO2 ? HNO3 NO3- followed by
  wet and dry deposition

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Nitrogen compounds

• Ammonia (NH3)
• strong odor at high concentrations. Produced
  naturally in biological decomposition (animal and
  their waste, soil) and biomass burning.
• Sink
• important implications to air quality and climate
  change, because of the formation of (NH4)2SO4and
  NH4NO3 particles which affect visibility and
  climate. (NH3 is the only basic gas to neutralize
  acid gases such as H2SO4 and HNO3.)
• Organic nitrates
• generated in smog pollution. PAN is important and
  can cause eye irritation and injure sensitive
  vegetation.
• CH3COOO NO2 M ? CH3OOONO2 (PAN)

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Relevance to Hong Kong

• NO2 is one of the three main air pollutants
  responsible for high air pollution index.

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Hydrocarbons and their Derivatives

• HCs containing only C and H atoms
• C1-C4 as gas under normal atmospheric conditions
• C5-C12 as volatile liquid
• C13 as solids (condensed on atmospheric aerosols)

Chemical structures
Aromatic HCs PAHs are carcinogins
Paraffinic HCs
Olefinic HCs
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Hydrocarbons and their Derivatives

• Produced by reaction of HCs with O2 and are major
  air pollutants. They include aldehydes, acids,
  alcohols, ethers, ketones, and esters.
• Both HCs and the derivatives are of a major
  concern because of their roles in urban
  photochemical smog. Some (e.g., benzene,
  formaldehyde) are toxic.
• NMHC non-methane hydrocarbons

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Hydrocarbons and their Derivatives

• Sources
• Anthropogenic
• mobile and stationary source fuel usage and
  combustion, petroleum refining and petrochemical
  manufacturing, industrial, commercial, and
  individual solvent use, gas oil production, and
  biomass burning. (In major urban areas, motor
  vehicle exhaust, gasoline spillage and
  evaporation, solvent use are often the major
  sources.) Oxygenated HCs can be emitted from
  vehicle exhaust as well as produced during the
  atmospheric oxidation of HCs.)
• Natural
• emissions from forest trees (mainly isoprene and
  monoterpenes), grassland (light paraffins and
  higher HCs) soils (mainly ethane), and ocean
  water (olefins and C9-C28 paraffins).

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Hydrocarbons and their Derivatives

• Sink
• through the oxidation on reaction with OH
  (hydroxyl radical) and O3 to form various
  aldehydes and acids which are in turn removed
  from the atmosphere by wet and dry deposition.
• The oxidation processes involved on the
  degradation of HC and oxy-HCs are very complex.
  They are very important in smog chemistry that
  are responsible for the formation of major
  photochemical oxidants including O3.

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Relevance to Hong Kong

• Toxic gases (monitored by EPD at several
  locations in HK)
• Photochemical smog

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Photochemical oxidants

• Produced in the atmosphere via
• HCs NOx O2 sunlight ? O3, NO2, PAN, H2O2,
  RO2 etc.
• Ozone (O3)
• the major component and has received major
  scientific and regulatory attention. It has
  important health and ecological implications.

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Ozone formation mechanism

• RH OH ? R H2O
• R O2 M ? RO2 M
• RO2 NO ? RO NO2
• RO O2 ? HO2 aldehydes and ketones
• HO2 NO ? NO2 O
• 2(NO2 hv ? NO O)
• 2 (O O2 M ? O3 M)
• Net RH 4O2 hv ? 2O3 H2O
  aldehydes/ketones
• NOx (NO NO2) serves as a catalyst in the above
  chain reaction.
• Major sink for O3 is surface deposition and
  chemical reactions involving UV photolysis and
  reaction with NO.

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Relevant to Hong Kong

• O3 is a major air pollution problem in HK and
  Pearl River Delta.

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Halogenated Hydrocarbons

• A variety of halogenated HCs are present in the
  atmosphere. They contain one or more atoms of Cl,
  Br, F.
• Some are toxic, and others can contribute to O3
  depletion and climate warming.
• Chlorofluorocarbons (CFCs) CFCl3 (CFC-11),
  CF2Cl2 (CFC-12), and C2Cl3F3 (CFC-113)
• low reactivity, low toxicity, thermal and solvent
  properties, widely used as aerosol propellants,
  refrigerant, degreasers, and foaming agents
• because of their roles in stratospheric ozone
  depletion, they are being phased out.

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Particulate Matter

• Particulate matter is a collective term used to
  describe small solid and liquid particles in the
  atmosphere.
• It is of a major air-quality concern because it
  is
• an inhalation hazard to humans and animals,
• reduces visibility,
• affects climate on regional and global scales.
• Particle size is a very important characteristics
  because it determines atmospheric lifetime,
  effects on light scattering, deposition in human
  lungs.

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Particle size distribution
Size characteristics of atmospheric particles

• Nuclei mode from condensation of low vapor
  pressure substances
• Accumulation modegrown from nuclei mode
  particles through coagulation and condensation
• Coarse modegenerated by mechanical processes

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Particulate Matter
TSP PM10 (RSP) PM2.5 (FSP)
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Particulate Matter

• Source
• Primary
• Natural volcanos, forest fires, ocean sprays,
  biologic sources (mold, pollen, bacteria etc.)
• Anthropogenic transportation, fuel combustion
  in stationary sources,and other activities such
  as industrial processes, construction and
  agricultural activity
• Secondary
• from chemical processes involving gases, aerosol
  particles and moisture

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Particulate Matter

• Chemical composition
• major components include organic and elemental
  carbon (OC and EC), sulfate, nitrate, and a
  variety of trace metal.
• In Hong Kong, C 50 of PM10 mass sulfate 17,
  nitrate6
• Sink
• wet and dry deposition

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Relevance to Hong Kong

• Particulate matter is a major air pollution
  problem in HK.
• Vehicles, particularly diesel vehicles, are the
  most important source.

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PM2.5 composition in background, urban and
roadside locations (Source HKEPD)
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References

• Thad Godish. 1997, Air Quality, Third Edition.
  Lewis Publishers
• Boubel R. W., Fox D. L. and Turner D. B. 1994,
  Fundamentals of Air Pollution. Academic Press
• Noel De Nevers, 2000, Air Pollution Control
  Engineering. 2nd edition. McGraw-Hill
• Environment Hong Kong 1995-2002, Environmental
  Protection Department of Hong Kong
• Air Quality in Hong Kong 1995-2002, Environmental
  Protection Department of Hong Kong
• K. A. Mulholland and K. Attenborough, Noise
  Assessment and Control. 1981. Construction Press