MEGACITY RESPIRATION Mexico City Example

1
MEGACITY RESPIRATION- Mexico City Example
-
AERODYNE RESEARCH, INC.
Prepared by C.E. Kolb Aerodyne Research,
Inc. Billerica, MA 01821-3976 Prepared
for Aerosol Workshop on Climate Prediction
Uncertainties Courtyard Santa Fe Santa Fe, NM
87507 July 21, 2006
ARI File No. VG/141
2
Motivating Concepts

• Urban Metabolism
• Cities consume materials and energy (food, fuel,
  electrical power, water, industrial materials,
  atmospheric oxygen, etc.)
• Cities export/excrete materials (industrial
  goods, sewage, garbage, industrial wastes,
  gaseous pollutants, and airborne
  particulates/aerosols)
• Urban Respiration
• Urban respiration (oxygen in/primary and
  secondary gaseous pollutants and airborne
  particulates/aerosols/out) represents the direct
  impacts of urban metabolism on the atmosphere
• Emitted urban air pollutants have a significant
  impact on both regional viability (human health,
  agricultural/ecosystem productivity, visibility),
  and global change (climate, ozone depletion,
  oxidative capacity) issues

3
Urban Respiration Exhalation Products
Gaseous Direct Green House Gases CO2, CH4,
N2O, CFCs Smog Precursors/Indirect Greenhouse
Gases NO, NO2, CO,
VOCs Photochemical Oxidants O3, NO2, H2O,
NO3, H2O2, ROOH Secondary Aerosol Precursors
SO2, NH3, HNO3, VOCs Particulates/Aerosols Smoke
/Soot Ash Road/Construction Dust Secondary
Aerosols
4
(No Transcript)
5
Megacity Statistics
Demographic and Transportation Indicators of
Worlds Megacities
Decker et al., Ann. Rev. Energy Environ. 25,
685-740 (2000).
6
Urban Air Chemistry
7
Urban Air Quality Status
8
Aerodyne Mobile Laboratory
Comprehensive gas and particle instrument suite

• Gas phase measurements
• CO2, CO, NO2, HNO3, NH3, O3, NO, NO2, NOy VOCs
• Particulate measurements
• Composition, mass loadings, size distributions,
  black carbon, number concentrations, absorption,
  scattering, surface area, PAH concentration
• Meteorological measurements
• Wind speed and direction, temperature, pressure,
  relative humidity
• Offline methods
• canister sampling
• filter sampling

9
Modes of Deployment

• ON-ROAD SAMPLING
• -On-road vehicle emissions quantification by
  vehicle and operating condition
• -Aggregate (fleet) motor vehicle pollutant
  emission ratios
• -Point and area emission plume source location
  dispersion measurement
• -Ambient pollutant mapping
• STATIONARY SAMPLING
• -Multiple site deployment during intensive study
• -High time resolution point sampling
• -Locate at hard to access sites
• -Co-located sampling with other researchers

Specific source emissions
MCMA basin and regional pollution
10
Aerodyne Fixed Site Measurement Locations During
MCMA 2006
11
Pico Tres Padres

• Photochemical processing of city emissions and
  secondary aerosol generation
• Source-specific wind-advected plumes and particle
  nucleation and growth

12
MCMA Air Pollution
13
Photochemical Processing at Pico Tres Padres
Photochemistry
Boundary layer rise
sun rise
Measurements above nighttime boundary layer
14
Oxidation Velocity!
We are not modelers yet, but it seems that HCHO
may be produced more rapidly than O3 And finally
the particle formation kicks in and endures
longest
15
CO, PM, and CO2 at PTP and T0
Diurnal profiles of CO, PM number density, and
CO2 at T0 and PTP. The T0 morning peaks of CO and
PM are well correlated with the CO2 peak since
they are primary emissions, whereas the afternoon
PM peak at PTP is heavily influenced by secondary
aerosol formation
16
O3, HCHO, and CO2 at T0 and PTP
Upper graph photochemically produced O3 forms in
the afternoon at both sites. Nighttime
concentrations are near zero at T0 due to nearby
NO sources. Middle graph The observed diurnal
profile of HCHO at T0 is a combination of both
directly-emitted and photochemically-formed HCHO,
evident by the delay of its temporal profile
after the T0 CO2 peak.
17
SO2 Plume With Wind Trajectories From
Popocatepetl
18
MCMA Fine PM Characterization

• Concentration and composition
• Ambient aerosol processing
• Soot particle evolution in MCMA atmosphere

19
MCMA-2003 CENICA PM2.5 Mass Loading
Salcedo, et al (2006)
20
MCMA-2003 CENICA PM2 Characteristics
Salcedo, et al. (2006)
21
MCMA-2003 CENICA Average PM2.5 Mass Composition
Salcedo, et al. (2006)
22
MCMA-2003 Fine PM Size Distribution
Salcedo, et al. (2006)
23
Mexico City Map
Measurements were obtained at several fixed sites
in Mexico City (Xalostoc, Merced, Cenica,
Pedregal, and Santa Ana) with differing
influences of air pollution sources and
meteorology.
24
Urban Aerosols City Center and Down Wind

• City center
• Light Industrial/ Residential urban
• Boundary site

Organics Sulfate Nitrate
Ammonium
25
Soot Particles Generated from Premixed Flame
26
Particle Shape can be Investigated Using Multiple
Physical Measurements
27
Primary Combustion Particles
Flame generated soot in the lab (Slowik et al,
2005 DeCarlo et al., 2005) Diesel particles
on the road (Canagaratna et al., 2003)
28
Organic Mass Distributions
m/z 57 C4H9
Morning Rush Hour
m/z 44 CO2
Traffic mode
Accumulation mode

• Small mode, hydrocarbon-based, primary traffic
  organic PM
• Accumulation mode oxidized organic PM

29
Aging of Fractal Combustion Particles
30
Mexico City Size Distributions
Polydisperse
Monodisperse (dm 200 nm)
3/29/06
830 AM 915 AM
730 AM 815 AM
630 AM 715 AM
530 AM 615 AM
31
Organic Analysis
Zhang et al., 2004.
32
Summary

• Developing World Megacities are a Growing Source
  of Fine Atmospheric PM
• Real-Time Fine PM and Gaseous Secondary PM
  Precursor Instrumentation can Characterize Urban
  PM Composition and Evolution
• Mobile Laboratory Real-Time Instrument
  Deployments can Characterize Spatial and Temporal
  Distributions of PM and PM Precursors
• Detailed Physical and Chemical Characterization
  of Ambient Urban PM can Track Evolution of
  Primary Soot

33
Acknowledgements
Tim Onasch, Scott Herndon, Ezra Wood, Doug
Worsnop, Mark Zahniser, Aerodyne Research,
Inc. Jose Jimenez, University of Colorado Miguel
Zavala, MIT Claudio Mazzoleni, Manvendra Dubey,
Los Alamos National Lab Berk Knighton, Montana
State University Dwight Thornhill, Lindsey Marr,
Virginia Tech Eduardo Deustúa, INE Jay Slowik,
Paul Davidovits, Boston College Dara Salcedo,
University of Autonoma Estado Morelos Pat Arnott
Desert Research Institute Funding NSF, DOE,
MCE Special Thanks To Rafael Ramos, Gustavo
Enrique Sosa Iglesias, Tomas Rangel, Ana
Patricia Martínez, Benjamin de Foy, and Luisa
Molina
34
Observed Traffic Mode in Size Distributions
Remote Site Mono-modal Aged-Transported
Urban Site Bi-modal Local Sources
Accumulation mode
Accumulation mode
Traffic mode
Scotland SASUA-3
ACE ASIA
Allan, Alfarra et al. (U. Manchester)
35
Particle Morphology Derived from Combination of
AMS and SMPS Measurements
AMS Aerodynamic Diameter Dva ? Dv / ?

• Dv volume eq. diameter (mass r p/6 Dv3)
• r particle density
• c dynamic shape factor (ratio of drag on
  particle to drag on volume equivalent sphere)

SMPS Mobility Diameter Dmob ? Dv
(Slowik et al, 2005 DeCarlo et al., 2005)
36
Organic Mass Spectra
m/z 57 C4H9
Morning Rush Hour
m/z 44 CO2
Traffic mode
Accumulation mode
Investigate specific mass spectra during morning
rush hour and late afternoon
37
Hydrocarbon and Oxidized Organics
38
Organic Mass Spectra
CnH2n0,2
----gt CmH2m1 27, 29, 41, 43, 55, 57, 69,
71, ... CnHmOy ----gt H2O , CO ,
CO2 , C2H3O 18 28 44
43 29, 55, .
e-
C4H9
C3H7
C3H5
e-
Following flash vaporization at 600oC