Abstract View
Submicron Aerosol Composition and Source Contributions across the Kathmandu Valley, Nepal
Benjamin Werden, Michael R. Giordano, Khadak Mahata, Md. Robiul Islam, Siva Praveen Puppala, Arnico Panday, Robert J. Yokelson, Elizabeth Stone, PETER F. DECARLO, Johns Hopkins University
Abstract Number: 653
Working Group: Remote and Regional Atmospheric Aerosol
Abstract
High levels of air pollution are observed throughout the Kathmandu valley of Nepal, with an average wintertime PM1 of 102 µg/m3 and daily peaks over 200 µg/m3. Differences in concentration and and source contributions measured across 3 separate sites within the Kathmandu Valley indicate the importance of multi-site measurements for understanding air quality across an air-shed. Using a mini-Aerosol Mass Spectrometer (mAMS) non-refractory PM1 (NR-PM1) was measured at 3 sites in the valley interior: Dhulikhel on the valley edge, Ratnapark in the city center, and suburban Lalitpur. Organic aerosol (OA) was the largest contributor to NR-PM1 mass, and BC the second largest component. OA is on average 49% of PM1 and BC 21%. The average background PM1 outside the valley was 48 µg/m3, with an average urban enhancement of 58 µg/m3. SO4 is 3.6 µg/m3 outside the valley, 7.5 µg/m3 in the urban center, and 12.0 µg/m3 in the suburban brick kiln region. Chl has an average concentration of 1.9 µg/m3 at background, 6.2 µg/m3 at Ratnapark, and 4.8 µg/m3 at Lalitpur, an increase of 3.3 and 2.5 times respectively. PMF identified seven OA factors: Four primary sources, and three secondary organic aerosol sources (SOA). Hydrocarbon-like OA (HOA), biomass burning OA (BBOA), trash burning OA (TBOA), and a local sulfate containing OA (sLOA) are the primary sources. OOA is over 50% of all mass outside the valley, and 36% within, making it the largest OA component. HOA is the largest primary OA source, contributing up to 21% of all OA, and 44% of BC. TBOA comprises 12% of OA, and 20% of BC, and BBOA is 15% of OA, and only 4% of all BC.