AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Wintertime PM2.5 in the Kathmandu Valley and Terai Region of Nepal
MD. ROBIUL ISLAM, Nita Khanal, Khadak Mahata, Siva Praveen Puppala, Narayan Babu Dhital, Michael Giordano, Benjamin Werden, Anobha Gurung, Arnico Panday, Robert J. Yokelson, Peter DeCarlo, Elizabeth Stone, University of Iowa
Abstract Number: 543 Working Group: Source Apportionment
Abstract Wintertime particulate matter composition and sources were examined in the Indo-Gangetic Plain (IGP) and Kathmandu Valley during the second Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE 2) from December 2017-February 2018. In Lumbini, located in the northern IGP, daily average PM2.5 and PM10 concentrations ranged 48-295 µg/m3 and 60-343 µg/m3, respectively, with organic carbon (OC) comprising 45% of PM2.5. By way of molecular markers, biomass burning, cow dung burning, and garbage burning were identified as major PM2.5 sources. Nitro-monoaromatic compounds, of interest due to their light-absorbing properties and toxicity were measured for the first time in the region. Three such species, 4-nitrocatechol (2-434 ng/m3), 4-methyl-5-nitrocatechol (0.1-201 ng/m3), and 5-nitrosalicylic acid (8-61 ng/m3) indicated the presence of secondary organic aerosol (SOA) associated with biomass burning. Additional SOA precursors included anthropogenic monoaromatic and diaromatic volatile organic compounds (VOCs) that had consistently larger SOA contributions than isoprene, monoterpenes, and sesquiterpenes. In Kathmandu, Lalitpur, and Dhulikhel in the Kathmandu Valley, PM2.5 and PM10 concentrations ranged 31-183 µg/m3, and 57-433 µg/m3, respectively, of which OC comprised 28-31%. Garbage burning, fossil fuel combustion, and biomass burning were identified as major PM2.5 sources. In comparison to Lumbini, the Kathmandu Valley had larger influences from garbage burning and fossil fuel sources and substantially lower influences from dung burning. Trends in SOA precursors were consistent across the Kathmandu Valley and IGP, with larger influences from anthropogenic VOCs compared to biogenic VOCs. Chemical mass balance modeling will be used for source apportionment to estimate source contributions to PM2.5 organic carbon during pollution events.