1. Source identification of aerosols in Mexico City
Bo Yao
April, 2007

2. Overview Particulate Matter MILAGRO field campaign description
Positive Matrix Factorization method
Results and Discussion
Future work

3. Particulate Matter
A complex mixture of suspended, condensed phase particles
Sources: natural and anthropogenic
Impacts:
health effects: fine particles (PM2.5)
climate: CCN
heterogeneous chemistry processes

4. Objectives Estimate the source contributions
Better understand the chemical composition of each source

5. MILAGRO field study – March, 2006
Measurements included:
T1 site, 30 km NE of Mexico City center (Tecamac University)
NCAR C-130 flights out of Veracruz

6. T1 Measurements TEOM mass
Inorganic ions: Na+, NH4+, Ca2+, Mg2+, Cl-, NO2-, NO3-, SO42-
Water Soluble Organic Carbon (WSOC),
OC, EC – Sunset Labs analyzer

7. Method
Positive Matrix Factorization (PMF)
X= GF + E or
to minimize

8. Method (continued) Explained variation
a magnitude of the contribution of each chemical species for each identified factor

9. Method (continued) Missing data and below detection:
missing data - replaced by the geometric mean of corresponding elements and four times the geometric mean as the corresponding errors
below detection – half of the detection limit used for below-detection-limit values and 5/6 of the detection limit used for the corresponding errors

10. Results

12. Future work
Rotation freedom
Time series
Gas phase species: e.g. HC’s