Chapter 7 Chemistry of urban and indoor atmospheres

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Chapter 7Chemistry of urban and indoor
atmospheres

• CH350/EV350
• Spring 2008

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WHO air quality guidelines

• Exposure concentration x time
• Concentration allowed over 8 hours will be less
  than that allowed for just 1 hour
• CO limit 10 mg/m3 for 8 hours
• CO limit 20 mg/m3 for 1 hour

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WHO air quality guidelines
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Air Quality in megacities (gt10 million)

• Sulfur dioxide (SO2)
• Bejing, Seoul, and Mexico City have ambient
  levels of SO2 that greatly exceed WHO guidelines
• Many cities restrict coal burning and dont have
  a problem with SO2

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Air Quality in megacities (gt10 million)

• Suspended particulate matter (SPM)
• 150-230 mg/m3 WHO guidelines
• 200-600 mg/m3 average
• Some exceed 1000 mg/m3 at times
• Beijing, Shanghai, and Seoul particles due to
  domestic heating
• Beijing, Cairo, Delhi, Karachi and Mexico City
  have high natural loadings of wind-blown
  particles
• London, New York, and Tokyo consistently met
  particle guidelines

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Air Quality in megacities (gt10 million)

• Carbon monoxide (CO)
• 10 mg/m3 WHO guidelines
• Concentrations vary significantly across the city
• Large amounts of automobiles generally contribute
  to higher amounts of CO, Mexico City, London, and
  New York

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Air Quality in megacities (gt10 million)

• Nitrogen dioxide (NO2) and ozone (O3)
• Not measured as much as other pollutants
• Mexico City, Los Angeles, and Sao Paulo, have
  short-term concentrations of NO2 and O3 that
  exceed WHO guidelines
• Mexico City had O3 at 900 mg/m3, four times the
  guideline of 200 mg/m3

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Air Quality in megacities (gt10 million)

• Lead (Pb)
• Dependent on number of cars and amount of lead in
  fuels
• Cairo and Karachi have excessive lead levels
• Many countries have removed lead from fuels or
  have plans to do so soon.
• Residuals of lead in soils near roads or fueling
  areas can be a problem

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Which city would be the worst to live in based on
atmospheric pollution?
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Mexico City

• Surrounded by mountains
• Little wind
• Often have temperature inversions
• Pollutants accumulate and often exceed WHO
  guidelines

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Mexico City SO2

• SO2 always above WHO guidelines
• Power plants burn high sulfur (3.5 S) fuel oil
• Buses and trucks burn diesel fuel with 1.2 S
• Power plants switching to natural gas (less
  sulfur)

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Mexico City suspended particles

• Particle concentrations always above WHO
  guidelines
• Large amount of natural particles (soil dust and
  biological particles)
• Domestic, industrial, and transportation
  combustions also significant sources of particles.

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Mexico City CO

• CO often a problem from morning rush hour
• High altitude of city (lower pressure) makes it
  more likely to have incomplete combustion
• Low pressure also contributes to adverse health
  effects related to CO.

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Mexico City NOx and O3

• NOx mainly from transportation.
• NOx not too much higher than WHO guidelines.
• Inversions often cause ozone problems 30 of days
  have ozone levels higher than national standards
• The southwest sector of city has 60 of days
  where ozone levels exceed standards.

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Mexico City Pb

• Amount of lead in atmosphere peaked in 1980
• Caused by lowering amount of lead allowed in
  fuels.

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Air Quality Index (AQI) in US

• CO, NO2, PM2.5, SO2, O3, and Pb measured to
  determine air quality.

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AQI criteria
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AQI Health Effects
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2007 AQI Data CA and MO (selected areas)
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2007 PM2.5 data for selected MO and CA cities
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AQI for US areas

• Any areas of interest?
• http//www.epa.gov/air/data/geosel.html

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Indoor air quality

• People spend a lot of time indoors
• Cooking, cleaning, heating by open or contained
  fires, smoking can cause changes in air quality

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Factors affecting indoor air quality

• Air outside
• If air outside is polluted (O3 as an example),
  some of that air will eventually get inside.
• Air exchange rate
• Some airy houses have many air exchanges per hour
• Pollutants generated inside are removed
• Very tightly insulated houses have only 0.1 0.5
  air exchanges per hour
• Pollutants generated inside tend to accumulate

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Air exchangers that conserve energy
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Air exchangers that conserve energy
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Factors affecting indoor air quality

• Construction materials
• Many plastics are sources of formaldehyde
• Clays are sources of radon
• Indoor activities
• Combustion for heating or cooking releases gases
  and/or particles
• Cooking foods releases gases and/or particles
• Smoking releases gases and/or particles
• Cleaning creates dust and releases volatile
  solvents

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Sources of pollutants to indoor air
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Common indoor air contaminantsRadioactivity

• Uranium-238 (t1/2 4.5 x 109 years) and Thorium
  -232 (t1/2 14 x 109 years) common in rocks and
  soils
• Lead to the production of radon through alpha
  decay

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Common indoor air contaminantsRadioactivity

• Radon is a noble gas (t1/2 3.8 days for
  radon-222)
• Migrates through cracks into buildings
• Inhaled into lungs

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Common indoor air contaminantsRadioactivity

• Radon decays to polonium and ultimately to
  lead-206 (which is stable)
• Polonium is not a gas and will remain in lungs if
  formed there
• Ultimately Rn decay in lungs will lead to 3-a
  particles, 4-b particles, and Pb remaining

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Common indoor air contaminantsVolatile organic
compounds

• VOCs come from construction materials, consumer
  products, and combustion processes
• Construction materials leading to VOC releases in
  New buildings is high
• Wood composites (chips and sawdust)
• Insulating foams
• Floor tiles
• Carpet
• Adhesives used in insulation
• Construction material VOCs include
• Chloroform
• Acetone
• Chlorinated compounds
• Formaldehyde

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Formaldehyde release from construction materials
decreases with time
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Formaldehyde from construction materials

• Sources of formaldehyde include resins for
  plywood and particle board, fire-retardant
  chemicals, color retention chemicals, some
  wallpapers, and urea formaldehyde (UF) polymers
• Release of formaldehyde is enhanced by
  temperature and humidity

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Formaldehyde and FEMA trailers used for Hurricane
Katrina victims

• FEMA used new mobile home trailers to help
  victims displaced by Hurricane Katrina
• Some of these trailers had high levels of
  formaldehyde emissions
• http//www.sierraclub.org/gulfcoast/downloads/form
  aldehyde_test.pdf
• http//www.fema.gov/media/archives/2007/051807.sht
  m
• http//www.homelandstupidity.us/2006/08/08/formald
  ehyde-in-fema-travel-trailers-making-people-sick/
• Question What did these people expect to get
  from the government, old worn out homes to live
  in or new temporary homes? It shouldnt be
  surprising that new homes in a hot humid climate
  have large VOC emissions!
• Does it not occur to people that air exchange
  rates are important and if people suspect they
  are getting sick from the air, they should open
  windows to get the bad air out!

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VOCs from Combustion

• Fuel to air ratio is important for VOC production
• CO common but hydrocarbons are also produced
• Ventilation of exhaust is important
• In many poor countries people use wood/coal fires
  to cook in house with no chimney
• Cigarette smoking releases aldehydes, ketones,
  organic bases, organic acids, and hydrocarbons

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Common indoor air contaminantsIndoor particles

• Particles can come from combustion of fossil fuel
  or biomass
• Wood stoves, smoking, other heating/cooking
  sources
• 100 mg/m3 acceptable standard
• 4 methods of cooking tortillas studied in rural
  Mexico
• 1140 mg/m3 for biomass fuel in unvented house
• 330 mg/m3 for liquefied petroleum gas in unvented
  house
• 540 mg/m3 for unvented biomass and liquefied
  petroleum gas
• 430 mg/m3 for vented biomass

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Particles produced during cooking

• Environ. Sci. Technol., 38 (8), 2304 -2311, 2004.
  
• Source Strengths of Ultrafine and Fine Particles
  Due to Cooking with a Gas Stove
• Lance A. Wallace, Steven J. Emmerich, and
  Cynthia Howard-Reed
• Selected parts of Abstract
• Cooking, particularly frying, is an important
  source of particles indoors.
• The selected cooking episodes (mostly frying)
  were capable of producing about 1014 particles
  over the length of the cooking period (about 15
  min), more than 90 of them in the ultrafine
  (lt0.1 m) range
• Frying produced peak numbers of particles at
  about 0.06 mm.
• Levels of PM2.5 were increased during cooking by
  a factor of 3.
• Breakfast cooking (mainly heating water for
  coffee and using an electric toaster) produced
  concentrations about half those produced from
  more complex dinnertime cooking.

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Particles produced during cooking

• Environ. Sci. Technol., 41 (1), 99 -105, 2007
• Compositions of Fine Particulate Organic Matter
  Emitted from Chinese Cooking
• Yunliang Zhao, Min Hu, Sjaak Slanina, and
  Yuanhang Zhang
• Selected parts from Abstract
• In this study, the chemical composition of
  particulate organic matter (POM) in PM2.5 emitted
  from four different Chinese cooking styles were
  examined by gas chromotography-mass spectrometry
  (GC-MS).
• The dominant homologue is fatty acids,
  constituting 7385 of the quantified compounds.
• The pattern of n-alkanes and the presence of
  -sitosterol and levoglucosan indicate that
  vegetables are consumed during Chinese cooking
  operations.
• The candidates of organic tracers used to
  describe and distinguish emissions from Chinese
  cooking in Guangzhou are tetradecanoic acid,
  hexadecanoic acid, octadecanoic acid, oleic acid,
  levoglucosan, mannosan, galactosan, nonanal, and
  lactones.
• During the sampling period, the relative
  contribution of Chinese cooking to the mass
  concentration of atmospheric hexadecanoic acid
  should be less than 1.3 in Guangzhou.

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Common indoor air contaminantsIndoor particles

• Soil dust
• Mold
• Lead paint
• Asbestos

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Collapse of World Trade Center in 2001

• Large amount of dust/particles created during the
  burning and collapse of towers

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Collapse of World Trade Center in 2001

• Dust even penetrated indoor environments of
  businesses and homes.

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Collapse of World Trade Center in 2001

• Particles contained
• Asbestos
• Polycyclic aromatic hydrocarbons (PAHs)
• polychlorinated biphenyls (PCBs)
• polybrominated dipheyl ethers (PBDEs)
• polybrominated dibenzo-p-dioxins (PBDDFs)
• tetra- and pentachlorinated biphenylenes (PCBPs)
• This has created public concern because WTC dust
  is thought to cause adverse pulmonary symptoms
  including "WTC cough" and reduced lung capacity.
  Pleil et al. 2006

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Particles from Laser printersEST
DOI10.1021/es802193nAuthor Lidia Morawska