AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Spatial Variation of Wintertime Aerosol Composition and Source Contribution across the Kathmandu Valley, Nepal
BENJAMIN WERDEN, Michael Giordano, Khadak Mahata, Siva Praveen Puppala, Arnico Panday, Robert J. Yokelson, Elizabeth Stone, Peter DeCarlo, Drexel University
Abstract Number: 690 Working Group: Source Apportionment
Abstract The Nepal Ambient Monitoring and Source Testing Experiment [NAMaSTE 2] in December 2017- February 2018 measured aerosol composition and source apportionment across the Kathmandu Valley, Nepal. Ambient measurements were made at three locations from urban, to suburban, and the rural valley edge.
The urban site, Ratnapark, was heavily impacted by traffic, and the observed average PM1 concentration was 74 ± 39.6 µg*m−3, consisting of 41% organics, 7% sulfate, 35% BC, 5% ammonium, 6% nitrate, and 5% chloride. The suburban site, Lalitpur, was subject to emissions from brick kilns; the average PM1 was 79.63 ± 38.7 µg*m−3, consisting of 44% organics, 11% sulfate, 26% BC, 7% ammonium, 8% nitrate, and 4% chloride. Dhulikhel, at the valley edge, had minimal influence from industry, and the average PM1 was 35.42 ± 14.4 µg*m−3, consisting of 56% organics, 8% sulfate, 17% BC, 6% ammonium, 10% nitrate, and 2% chloride.
Positive Matrix Factorization identified several distinct factors for the organic mass spectra measured. Commonly observed Organic Aerosol (OA) factors identified were, Hydrocarbon (HOA), Cooking (COA), Coal Combustion (CCOA), Biomass Burning (BBOA), and both semi- and low-volatile oxygenated OA (SV-OOA, LV-OOA). HOA increased at all sites during rush hours, as did COA during meal times. LV-OOA was a consistently observed background aerosol in the valley. Overnight increases of CCOA and sulfates were seen and BBOA concentrations increased substantially overnight. Trash burning was a significant factor in the urban environment.
Differences in source concentration at each measurement location is important to document so that effective mitigation measures can be designed appropriately across the region.