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Werden B, Giordano MR, Mahata K, Islam MR, Goetz JD, Puppala SP, Saikawa E, Panday AK, Yokelson RJ, Stone EA, DeCarlo PF. Submicron Aerosol Composition and Source Contribution across the Kathmandu Valley, Nepal, in Winter. ACS EARTH & SPACE CHEMISTRY 2023; 7:49-68. [PMID: 36704179 PMCID: PMC9869769 DOI: 10.1021/acsearthspacechem.2c00226] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 11/23/2022] [Accepted: 11/28/2022] [Indexed: 06/17/2023]
Abstract
The Kathmandu valley experiences an average wintertime PM1 concentration of ∼100 μg m-3 and daily peaks over 200 μg m-3. We present ambient nonrefractory PM1 chemical composition, and concentration measured by a mini aerosol mass spectrometer (mAMS) sequentially at Dhulikhel (on the valley exterior), then urban Ratnapark, and finally suburban Lalitpur in winter 2018. At all sites, organic aerosol (OA) was the largest contributor to combined PM1 (C-PM1) (49%) and black carbon (BC) was the second largest contributor (21%). The average background C-PM1 at Dhulikhel was 48 μg m-3; the urban enhancement was 120% (58 μg m-3). BC had an average of 6.1 μg m-3 at Dhulikhel, an urban enhancement of 17.4 μg m-3. Sulfate (SO4) was 3.6 μg m-3 at Dhulikhel, then 7.5 μg m-3 at Ratnapark, and 12.0 μg m-3 at Lalitpur in the brick kiln region. Chloride (Chl) increased by 330 and 250% from Dhulikhel to Ratnapark and Lalitpur on average. Positive matrix factorization (PMF) identified seven OA sources, four primary OA sources, hydrocarbon-like (HOA), biomass burning (BBOA), trash burning (TBOA), a sulfate-containing local OA source (sLOA), and three secondary oxygenated organic aerosols (OOA). OOA was the largest fraction of OA, over 50% outside the valley and 36% within. HOA (traffic) was the most prominent primary source, contributing 21% of all OA and 44% of BC. Brick kilns were the second largest contributor to C-PM1, 12% of OA, 33% of BC, and a primary emitter of aerosol sulfate. These results, though successive, indicate the importance of multisite measurements to understand ambient particulate matter concentration heterogeneity across urban regions.
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Affiliation(s)
- Benjamin
S. Werden
- Department
of Civil, Architectural, and Environmental Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States
| | - Michael R. Giordano
- Department
of Civil, Architectural, and Environmental Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States
| | - Khadak Mahata
- International
Centre for Integrated Mountain Development, Khumaltar, Lalitpur, 44700Kathmandu, Nepal
| | - Md. Robiul Islam
- Department
of Chemistry, University of Iowa, 230 North Madison Street, Iowa City, Iowa52242-1294, United States
| | - J. Douglas Goetz
- Department
of Civil, Architectural, and Environmental Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States
| | - Siva Praveen Puppala
- International
Centre for Integrated Mountain Development, Khumaltar, Lalitpur, 44700Kathmandu, Nepal
| | - Eri Saikawa
- Department
of Environmental Sciences, Emory University, 400 Dowman Drive, Atlanta, Georgia30322, United States
| | - Arnico K. Panday
- International
Centre for Integrated Mountain Development, Khumaltar, Lalitpur, 44700Kathmandu, Nepal
| | - Robert J. Yokelson
- Department
of Chemistry, University of Montana, 32 Campus Drive, Missoula, Montana59812, United States
| | - Elizabeth A. Stone
- Department
of Chemistry, University of Iowa, 230 North Madison Street, Iowa City, Iowa52242-1294, United States
| | - Peter F. DeCarlo
- Department
of Civil, Architectural, and Environmental Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania19104, United States
- Department
of Environmental Health and Engineering, John Hopkins University, 3400 North Charles Street, Baltimore, Maryland21218, United States
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