Volume 16, No. 1, January 2016, Pages 114-124 PDF(1.45 MB)
Contribution of Biomass Burning to Carbonaceous Aerosols in Mexico City during May 2013
Zitely A. Tzompa-Sosa1, Amy P. Sullivan1, Armando Retama2, Sonia M. Kreidenweis1
1 Department of Atmospheric Science, Colorado State University, 3915 W. Laporte Ave., Fort Collins, CO 80523, USA
2 Direccion de Monitoreo Atmosferico, Secretaria del Medio Ambiente, Gobierno del Distrito Federal, Avenida Tlaxcoaque #8, Sexto Piso, Colonia Centro, Delegacion Cuauhtemoc, Distrito Federal, 06090, Mexico
- Springtime fires contribute significantly to ambient WSOC and PM in MCMA.
- May 2013 was a particularly active fire month in Mexico.
- Wildfires and agricultural burning were the main biomass burning sources.
- Biomass burning tracers were strongly correlated with ambient concentrations of PM.
- Estimated contributions of biomass burning to WSOC ranged from 7–57%.
During the springtime fire season, wildfires and agricultural burning represent a potentially large contribution to air quality degradation in the Mexico City Metropolitan Area (MCMA). PM10 filter samples were collected at six different stations in May 2013, the month with the maximum reported regional fire counts from 2002 to 2013. Two regimes were identified considering changes in predominant wind direction and precipitation patterns inside MCMA. The filter samples were analyzed for water-soluble organic carbon (WSOC) and the biomass burning tracers including levoglucosan (LEV) and water-soluble potassium (WSK+). LEV concentrations correlated positively with ambient concentrations of PM2.5 and PM10 (R2 = 0.61 and R2 = 0.46, respectively). Strong correlations were also found between WSOC and LEV (R2 = 0.94) and between WSK+ and LEV (R2 = 0.75). PM2.5 accounted for 60% of the PM10 mass concentrations. Our speciated measurements accounted for 37% of the total PM10 mass concentration and ~60% of the PM2.5 mass concentrations; the missing mass was attributed to crustal material (soil or dust) and carbonaceous aerosols that were not segregated into the WSOC fraction. Average LEV/WSOC ratios ranged from 0.015 in the first, smokier and drier part of the month, to 0.006 during the rainier end of the measurement period. Using previously reported LEV/WSOC emissions ratios, the estimated biomass burning contributions to WSOC ranged from 7–23% assuming LEV is stable in the atmosphere, and 8–57% when accounting for LEV photochemical degradation in the atmosphere. Thus, our findings indicate that primary emissions from biomass burning sources represent significant contributions to ambient WSOC and PM in MCMA during the springtime fire season.
Levoglucosan; Water-soluble organic carbon; Potassium; Air quality.