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

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

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

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

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

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

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

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

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

Results

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