Air Pollution
 
Lecture No.: air pollution
 
 
1. Definition
 Any substance in the air that causes damages to health and properties.
2. Types of Pollutants
 (1) sulfurous type (London type)
  A. SOx and sulfates.
 B. coal fuel.
 C. high relative humidity.
 D. pea-soup smog.
 (2) photochemical smog (Los Angeles type)
 A. ozone, PAN, NOx, etc.
 B. strong solar radiation.
3. Pollution Sources
 (1) Natural sources: 90%
 (2) Anthropogenesis sources (human activity): 10%
 A. particulates (aerosols)
  (A) any solid and liquid materials in the air.
  (B) major sources:
  stationary sources (industrial plants and power plants).
 B. sulfur oxides (SOx)
  (A) SO2 and SO3
  (B) major sources:
 stationary sources(power plants and industrial plants)
 C. nitrogen oxides (NOx)
  (A) NO and NO2
  (B) major sources:
 transportation and power plants.
  (C) emission has increased since 1970.
 D. hydrocarbon (HC)
  (A) volatile organics (methane).
  (B) major sources:
  industrial plants and transportation.
 E. carbon monoxide (CO)
  (A) CO
  (B) major sources:
 Transportation.
4. Pollution Potential
 (1) Holzworth's definition:
 C/Q = L/UH
 C: pollution concentration.
 Q: emission rate.
 L: city size along wind dimension (10 km or 100 km).
 U: wind speed.
 H: mixing height (height to which an air parcel can rise).
 (2) Oregon: the highest pollution potential in the United States.
 (3) C/Q is determined by meteorological (weather) factors only.
5. Pollution Units
 (1) parts per million (ppm):
 2 ppm: 2 m3 pollutant in one million m3 air 
 (2) µg/m3 (microgram pollutant per cubic meter air) 
 1 µg = 10-6 gram
 (3) conversion equation (at 1013 mb and 25 oC)
 µg/m3 = (ppm x molecular weight/22.4) x 103
 * the denominator is 22.4 at 0 oC and 1013 mb.
6. Pollution Standard Index (PSI)
 (1) Definition
 A numerical scale of 0-500 corresponding to various pollution
 concentrations.
 (2) Example (ozone)
 A. good air quality: 50 psi (= 0.06 ppm) or lower.
 B. moderate air quality: 100 psi (= 0.12 ppm) or lower.
 C. unhealthful: 113-188 psi (0.13 - 0.19 ppm).
 D. very unhealthful: 200-295 psi (0.20 - 0.39 ppm).
 E. hazardous: 300 - 500 psi (0.40 -0.60 ppm).
7. Pollution Episodes
 (1) The concentration of an air pollutant has reached a level
 at which a potential health hazard exists.
 (2) Episode levels
 A. stage 1 (health advisory): 0ne-hour average ozone ³ 0.20 ppm.
 B. stage 2 (warning): Ozone ³ 0.35 ppm. 
 C. stage 3 (emergency): ozone ³ 0.50 ppm.
 (3) notify school authority and the public.
8. Air Quality Index (AQI implemented since July 23, 1999 by EPA)
 (1). AQI is calculated for the 6 criteria pollutants according to
  the EPA formulas. The highest AQI value is adopted as the daily
  AQI. Foe example, if the AQI for ozone is 90 and 88 for SO2
   The reported AQI is 90.
 (2). Incorporates the new Federal ozone (8-hour average) and PM2.5
  standards.
 (3). Add a category, unhealthy for Sensitive Groups (101 to 150),
  to PSI Unhealthy category (101 to 199)
   Good: 0 to 50, Green color
  Moderate: 51 to 100, yellow color
  Unhealthy for Sensitive Groups: 101 to 150, orange color
  Unhealthy: 151 to 200, red color
  very Unhealthy: 201 to 300, purple color
  Hazardous: 301 to 500, maron color.
 Please click the following URL:
 http://www.arb.ca.gov/html/aqi.htm
 http://www.epa.gov/airnow/aqibroch/
9. National Ambient Air Quality Standard for ozone (NAAQS)
 (1) Primary standard: to protect public health.
  One-hour average ozone > 0.12 ppm for federal standard.
 One-hour average ozone > 0.09 ppm for state standard.
 (2) Secondary Standard: to protect public welfare.
 Please click the following URL
 http://www.epa.gov/air/criteria.html
 http://www.arb.ca.gov/html/fslist.htm
10. New National Ambient Air Quality Standard for ozone
 8-hour average > 0.08 ppm.
 Very close to the California state standard.
11. Geographical Setting of the South Coast Air Basin (SCAB)
 (1).  The SCAB comprises the non-desert portions of Los Angeles,
   Riverside, and San Bernardino Counties and all of Orange 
   County.
 (2).  Area: 6600 miles2.
 (3). Population: 1.4 millions in 1997.
 (4). Topography:
  A. West: The Pacific Ocean and Santa Monica Mountain.
  B. North: The San Gabriel and San Bernardino Mountains.
  C. South and East: The San Jacinto and Santa Ana Mountains.
12. Emissions:
 (1). Major sources:
  A. CO: Transportation.
  B. HC: Transportation.
  C. NOx: Transportation.
  D. SO2: Stationary.
  E. Particulates: Stationary (slightly greater than transportation).
 (2). Emission Trend (Since 1950):
  A. A substantial reduction has been achieved.
  B. SO2 meets the state and federal air quality standard.
  C. More reductions in emissions are needed for other pollutants.
13. Meteorology
 (1).  Poor Ventilation
  A. Light wind hampers the horizontal dispersion (dilution).
 (A). Civic Center (LA): 5.6 mph in average.
  (B). Central New York: 9.8 mph.
 (C). San Francisco: 8.7 mph.
  B. Persistent and strong inversion hinders the vertical mixing.
 (A). Low –level inversion (2,500 feet or lower)occurs 257
  days per year.
 (B). Winter:
  Surface inversion: 2 out of 3 days.
  Primary pollutants that emit directly from sources peak 
  in winter: VOC (volatile organic compound or reactive 
  hydrocarbon, RHC), CO, NOx, SOx, and particulates (PM10).
 (C). Summer:
  More frequent inversion but at a higher altitude (almost
  every day).
  Strong inversion magnitude (12 oC): the maximum temperature 
  in the inversion layer minus inversion base temperature.
  (2). Strong solar radiation
  A. Promotes photochemical(Secondary) smog (ozone, PAN, 
 and aldehyde)
  B. Chimney effect: The vertical penetration of smog through 
 the inversion layer on the south slope of the San Gabriel and 
 San Bernardino Mountains caused by the strong solar heating 
 in the afternoon.
  (3). Correlations between weather variables and ozone concentrations
  A. Better correlation in summer and at inland stations.
  B. Most important variables for ozone prediction: 850-mb
 (about 5,000 feet high)temperature.
 950-mb temperature, inversion base height, inversion magnitude, 
 and maximum mixing height also show significant correlations 
 with ozone concentration.
14. Pollutant types
 (1). Primary pollutants
  Those pollutants directly emitted from various sources:
  VOC (Volatile Organic compound) or RHC (reactive hydrocarbon),
  NOx, SOx, CO, and particulates (PM10 or PM2.5, particulates or 
  aerosols with diameter 10 microns or 2.5 microns, any solid 
  and/or liquid particles suspended in the air).
 (2). Secondary pollutants
 Those pollutants that are formed in the air through 
 photochemical reactions):
 Ozone, aldehyde, and PAN, etc.
 (3). Criteria pollutants (6 pollutants):
 The pollutants that have National Ambient Air Quality Standards
 established by the EPA: CO, NO2, SO2, ozone, lead, and
 PM (particulates, PM10 and PM2.5). Please click the URL
 http://www.epa.gov/air/urbanair/6poll.html
 (4). Ozone precursors
 The pollutants that generate ozone through the photochemical
 Reactions in the air: VOC (RHC) and NOx (NO2).
 (5). Oxidant
  Ozone plus PAN (peroxyacetyl nitrate).
 Since PAN concentration is small compared to ozone in the
 air, hence, the terms oxidant and ozone were interchangeable
 before 1978 in Los Angeles. At that time, KI method is used to 
 detect ozone in the air. KI method actually measures oxidant.
15. Spatial variations of LA smog [smog means (smoke + fog) originally.
 It means pollutant now]
 (1) Ozone increases from coastal areas to inland valleys (foothills 
 of the San Gabriel and San Bernardino Mountains).
 A. Locally generated ozone (higher temperature).
 B. Advection of ozone from the coastal and metropolitan areas by 
  sea breezes during the day (downwind of the most populated area).
 C. The worst ozone area has shifted from the decade mean of 58 pphm 
  in Downtown LA in the late 1950s, through the San Gabriel Valley 
 (Pasadena, Azusa, and Fontana) in the 1960s, 1970s, and 1980s, 
  to 25 pphm at Crestline (the San Bernardino Mountain) in the 
  1990s.
 D. There has been about 57% reduction in the decade means of 
  maximum ozone concentration since the late 1950s.
 E. Individual years
  Ozone has declined from 68 ppm in downtown LA in 1955 to 17 
  Pphm at Crestline in 1999, a 67% reduction.
 (2) Primary pollutants (CO, NOx, SOx, particulates)
 The worst polluted stations:
 A. CO: Lynwood.
 B. PM10: Riverside and San Bernardino.
 C. NO2: similar to ozone spatial distribution but with maximum
    around downtown Los Angeles and Lynwood.
 D.  SO2: Long Beach and Lynwood.
16. Temporal Variation
 (1) Seasonal variation
  A. Ozone: maximum in summer (May to October, ozone season).
  B. Primary pollutants: winter maximum.
 (2)  Diurnal Variation
  A. Ozone: 
  (A). Maximum at noon in coastal areas. 
  (B). Afternoon maximum in the inland valley or foothill
  areas.
  (C). Palm Spring (Coachella Valley): 4-5 p.m. (sea
  breezes).
 B. Primary pollutants:
  Related to traffic hours:
  (A). Primarily maximum: 7-9 a.m. 
  (B). Secondary maximum: 4-6 p.m.
 (3).Weekend vs Weekday
 A. Primary pollutants decreases on weekend.
 B. Ozone
  LA County: Ozone increases on weekend due to the reduction of
   NO in the air that may destroy ozone; 
 (NO + O3 à NO2 + O2). Less NO in the air on weekend
 results in less O3 destruction.
  Other Counties: Ozone decreases on weekend.
 (3) Secular trends
 A. Ozone
  (A). Has declined significantly since the late 1950s with a more
  steadily decline since 1979 when the first AQMP (Air
  Quality Management Plan) was implemented.
  (B). Absence of the 2nd stage episode day has occurred since 1989.
  (C). More pronounced decline since 1989.
  (D). Accelerated decline since 1996 when the reformulated
   gasoline was used.
 B. Primary pollutants: have declined.
 C. Pollutants exceeding federal air quality standard in 2003:
  Ozone and PM10
 
 Please click the following link for more information
 http://www.epa.gov/air/oaqps/index.html