# Presentation: 944825

## MEGACITY RESPIRATION- Mexico City Example -

**MEGACITY RESPIRATION****- Mexico City Example -**

***AERODYNE RESEARCH, INC.***

- ARI File No.
- VG/141

**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**

## Motivating Concepts

**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

## Urban Respiration Exhalation Products

**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

## Megacity Statistics

**Megacity Statistics**

- Demographic and
- Transportation Indicators
- of World’s Megacities

- Decker et al., Ann. Rev. Energy Environ. 25, 685-740 (2000).

## Urban Air Chemistry

| Primary Emissions | Sources | Secondary Pollutants | Effects |
| --- | --- | --- | --- |
| Sulfur Dioxide (SO2) | Power Plants, Vehicles, Industry | Sulfuric Acid Vapor, Sulfate Particles | Acid Rain, Heart/Lung Disease, Haze, Climate Change |
| Nitrogen Oxides (NOx) | Power Plants, Vehicles, Trash Burning, Industry | Nitric Acid Vapor, Nitrate Particles | Acid Rain, Heart/Lung Disease, Smog, Haze, Climate Change |
| Volatile Organic Compounds (VOCs) | Vehicles, Industry, Painting, Cleaning, Cooking | Organic Air Toxics, Organic Particles | Smog, Heart/Lung Disease, Haze, Climate Change |
| Ammonia       (NH3) | Vehicles, Human and Animal Waste | Ammonium Sulfate, Nitrate, Particles | Haze, Heart/Lung Disease, Climate Change |

## Urban Air Quality Status

| Factor | Developed World | Developing World |
| --- | --- | --- |
| Emissions | Most Large Sources Identified, Poor to Fair Knowledge of Temporal and Spatial Distributions Emissions Data Often Outdated | Some Sources Identified, Many Unknown, Little Knowledge of Temporal and Spatial Distributions, Emissions Data Suspect, Sources May Change Rapidly |
| Ambient Concentrations | Monitoring Stations Provide Data at Selected Sites, Indicate Trends | Monitoring Stations are New or Nonexistent, Trends are Unquantified |
| Management Strategies | Established, Based on Computer Model Analyses and Emissions Control | Emerging, Modeled on Developed World Strategies with Much Less Data |

## 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

## Modes of Deployment

**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**

## Aerodyne Fixed Site Measurement Locations During MCMA 2006

## Pico Tres Padres

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

## MCMA Air Pollution

## Photochemical Processing at Pico Tres Padres

**sun rise**

**Boundary layer rise**

**Photochemistry  **

**Measurements above nighttime boundary layer**

## 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

## CO, PM, and CO2 at PTP and T0

**The T0 morning peaks of CO and PM are well correlated with the CO****2**** peak since they are primary emissions, whereas the afternoon PM peak at PTP is heavily influenced by secondary aerosol formation**

**CO, PM, and CO****2 ****at PTP and T0**

## O3, HCHO, and CO2 at T0 and PTP

- 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.

**O****3****, HCHO, and CO****2**** at T0 and PTP**

## SO2 Plume With Wind Trajectories From  Popocatepetl

## MCMA Fine PM Characterization

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

## MCMA-2003 CENICA PM2.5 Mass Loading

**MCMA-2003 CENICA PM****2.5**** Mass Loading**

**Salcedo, et al **
**(2006)**

## MCMA-2003 CENICA PM2 Characteristics

**MCMA-2003 CENICA PM****2**** Characteristics**

**Salcedo, et al. (2006)**

## MCMA-2003 CENICA Average PM2.5 Mass Composition

**MCMA-2003 CENICA ****Average PM****2.5**** Mass Composition**

**Salcedo, et al. (2006)**

## MCMA-2003 Fine PM Size Distribution 

**MCMA-2003 ****Fine PM Size Distribution **

**Salcedo, et al. (2006)**

## 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.

**Notes:**
Need flat MC2003 map showing city
Only put on Merced, Cenica, Santa Ana
Merced – center
CENICA – residential
Santa Ana – edge
Air flow is typically north to south during day.

## Urban Aerosols – City Center and  Down Wind

**Urban Aerosols – ****City Center and  Down Wind**

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

-      Organics        Sulfate         Nitrate          Ammonium

**Notes:**
Don’t talk about dynamics, except for air flow

Reorganize to vertical like slide 18

## Soot Particles Generated from Premixed Flame

## Particle Shape can be Investigated Using Multiple Physical Measurements

**Particle Shape can be Investigated Using Multiple Physical Measurements**

## 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)***

**Primary Combustion Particles**

**Notes:**
Get full references
Note that flame mode is same Dva for different Dmob 
Note that fractal dimension = 1.8

## Organic Mass Distributions

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

- Morning Rush Hour

- Accumulation mode

- m/z = 57
- C4H9+

- ‘Traffic’ mode

- m/z = 44
- CO2+

**Notes:**
Add time grids on top graph
Add dark lines to show two modes for each.
Same size dist as before, but in time.

## Aging of Fractal Combustion Particles 

**Notes:**
Potentially replace bottom panel with a mixed secondary + minor primary, as observed in Urban.  This is rural...

## Mexico City Size Distributions

**Polydisperse**

**Monodisperse (d****m**** ~ 200 nm)**

**Mexico City Size Distributions**

- 5:30 AM – 6:15 AM

- 6:30 AM – 7:15 AM

- 8:30 AM – 9:15 AM

- 7:30 AM – 8:15 AM

_**3/29/06**_

## Organic Analysis

*Zhang et al., 2004*.

**Notes:**
Refer’s to Qi’s talk.

## Summary

**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

## Acknowledgements

**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

## Observed ‘Traffic’ Mode in Size Distributions

**Scotland *****SASUA-3***

- Remote Site *Mono-modal *
*Aged-Transported*

- Urban Site *Bi-modal** *
*Local Sources*

***ACE ASIA***

***Allan, Alfarra et al. (U. Manchester)***

- Accumulation mode

- Accumulation mode

- ‘Traffic’ mode

**Notes:**
Likely – largely internally mixed
Add lines to indicate two modes
Some of first data we got, 2000 and 2001

## Particle Morphology Derived from Combination of AMS and SMPS Measurements

***AMS:  Aerodynamic Diameter***
-     *D**va** ~ **** D**v** / ***

***SMPS:  Mobility Diameter***
-    *D**mob** ~ **** D**v** *

***D******v*****  **= volume eq. diameter (**mass = ********/6 D****v****3****)**
********  **=  particle density
******   **=  dynamic shape factor (ratio of drag on particle to drag on volume equivalent sphere)

***(Slowik et al, 2005; DeCarlo et al., 2005)***

**Notes:**
Not exact equations (no Cc)
X > 1.0
Dmob larger than Dv
Dva is less than Dv

## Organic Mass Spectra

**Organic Mass Spectra**

- m/z = 44
- CO2+

- Accumulation mode

- ‘Traffic’ mode

- m/z = 57
- C4H9+

- Morning Rush Hour

- Investigate specific mass spectra
- during morning rush hour and late afternoon

**Notes:**
Add time grids on top graph
Add dark lines to show two modes for each.
Same size dist as before, but in time.

## Hydrocarbon and Oxidized Organics

## Organic Mass Spectra

- CnH2n+0,2  ---->  CmH2m±1**+**
**	****	****	*****27, ******29******, ******41, ******43******, 55, ******57******,****** ******69******, ******71******, ...***
- CnHmOy  ---->   H2O+ ***,*** CO+ ***,*** CO2**+**** *****,***** **C2H3O+
**	****	****	****    *****18      28 *****       *****44****** ****** ******       43   ***
***	******	******	******	******	******	******29, 55******,  ....***

**Organic Mass Spectra**

*Following flash vaporization at  ~600**o**C*

- e-

- e-

**C****4****H****9****+**

**C****3****H****7****+**

**C****3****H****5****+**

**Notes:**
CnH2n+1 and CnH2n-1 (delta 2 and delta 0) for HC’s