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Journal article
Ambient air quality in the Kathmandu Valley, Nepal, during the pre-monsoon: concentrations and sources of particulate matter and trace gases
Atmospheric chemistry and physics, v 20(5), pp 2927-2951
11 Mar 2020
Featured in Collection : UN Sustainable Development Goals @ Drexel
Abstract
The Kathmandu Valley in Nepal is a bowl-shaped urban basin that experiences severe air pollution that poses health risks to its 3.5 million inhabitants. As part of the Nepal Ambient Monitoring and Source Testing Experiment (NAMaS 1E), ambient air quality in the Kathmandu Valley was investigated from 11 to 24 April 2015, during the premonsoon season. Ambient concentrations of fine and coarse particulate matter (PM2.5 and PM10, respectively), online PM1, inorganic trace gases (NH3, HNO3, SO2, and HCI), and carbon-containing gases (CO2, CO, CH4, and 93 nonmethane volatile organic compounds; NMVOCs) were quantified at a semi-urban location near the center of the valley. Concentrations and ratios of NMVOC indicated origins primarily from poorly maintained vehicle emissions, biomass burning, and solvent/gasoline evaporation. During those 2 weeks, daily average PM2.5 concentrations ranged from 30 to 207 mu g m(-3), which exceeded the World Health Organization 24 h guideline by factors of 1.2 to 8.3. On average, the nonwater mass of PM2.5 was composed of organic matter (48 %), elemental carbon (13 %), sulfate (16 %), nitrate (4 %), ammonium (9 %), chloride (2 %), calcium (1 %), magnesium (0.05 %), and potassium (1 %). Large diurnal variability in temperature and relative humidity drove corresponding variability in aerosol liquid water content, the gas-aerosol phase partitioning of NH3, HNO3, and HCI, and aerosol solution pH. The observed levels of gas-phase halogens suggest that multiphase halogen-radical chemistry involving both Cl and Br impacted regional air quality. To gain insight into the origins of organic carbon (OC), molecular markers for primary and secondary sources were quantified. Levoglucosan (averaging 1230 +/- 1154 ng m(-3)), 1,3,5-triphenylbenzene (0.8 +/- 0.6 ng m(-3)), cholesterol (2.9 +/- 6.6 ng m(-3)), stigmastanol (1.0 +/- 0.8 ng m(-3)), and cis-pinonic acid (4.5 +/- 1.9 ng m(-3)) indicate contributions from biomass burning, garbage burning, food cooking, cow dung burning, and monoterpene secondary organic aerosol, respectively. Drawing on source profiles developed in NAMaS 1E, chemical mass balance (CMB) source apportionment modeling was used to estimate contributions to OC from major primary sources including garbage burning (18 +/- 5 %), biomass burning (17 +/- 10 %) inclusive of open burning and biomass-fueled cooking stoves, and internal-combustion (gasoline and diesel) engines (18 +/- 9 %). Model sensitivity tests with newly developed source profiles indicated contributions from biomass burning within a factor of 2 of previous estimates but greater contributions from garbage burning (up to three times), indicating large potential impacts of garbage burning on regional air quality and the need for further evaluation of this source. Contributions of secondary organic carbon (SOC) to PM2.5 OC included those originating from anthropogenic precursors such as naphthalene (10 +/- 4 %) and methylnaphthalene (0.3 +/- 0.1 %) and biogenic precursors for monoterpenes (0.13 +/- 0.07 %) and sesquiterpenes (5 +/- 2 %). An average of 25 % of the PM2.5 OC was unapportioned, indicating the presence of additional sources (e.g., evaporative and/or industrial emissions such as brick kilns, food cooking, and other types of SOC) and/or underestimation of the contributions from the identified source types. The source apportionment results indicate that anthropogenic combustion sources (including biomass burning, garbage burning, and fossil fuel combustion) were the greatest contributors to PM2.5 and, as such, should be considered primary targets for controlling ambient PM pollution.
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Details
- Title
- Ambient air quality in the Kathmandu Valley, Nepal, during the pre-monsoon: concentrations and sources of particulate matter and trace gases
- Creators
- Md Robiul Islam - University of IowaThilina Jayarathne - University of IowaIsobel J. Simpson - University of California, IrvineBenjamin Werden - Drexel Univ, Dept Civil Architectural & Environm Engn, Philadelphia, PA 19104 USAJohn Maben - University of VirginiaAshley Gilbert - University of IowaPuppala S. Praveen - International Centre for Integrated Mountain DevelopmentSagar Adhikari - International Centre for Integrated Mountain DevelopmentArnico K. Panday - International Centre for Integrated Mountain DevelopmentMaheswar Rupakheti - Research Institute for Sustainability at GFZDonald R. Blake - University of California, IrvineRobert J. Yokelson - University of MontanaPeter F. DeCarlo - Drexel University, Civil, Architectural, and Environmental EngineeringWilliam C. Keene - University of VirginiaElizabeth A. Stone - University of Iowa
- Publication Details
- Atmospheric chemistry and physics, v 20(5), pp 2927-2951
- Publisher
- Copernicus Gesellschaft Mbh
- Number of pages
- 25
- Grant note
- AGS-1351616; AGS-0003865; AGS-1349976; AGS-1461458 / National Science Foundation; National Science Foundation (NSF) ICIMOD by the government of United Kingdom ICIMOD by the government of Norway ICIMOD by the government of Afghanistan ICIMOD by the government of Bhutan ICIMOD by the government of Nepal ICIMOD by the government of Bangladesh ICIMOD by the government of Austria Government of Sweden to ICIMOD's Atmosphere Initiative Institute for Advanced Sustainability Studies (IASS) - German Ministry of Education and Research (BMBF); Federal Ministry of Education & Research (BMBF)
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Civil, Architectural, and Environmental Engineering
- Web of Science ID
- WOS:000519886100001
- Scopus ID
- 2-s2.0-85081931719
- Other Identifier
- 991021860769404721
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- Collaboration types
- Domestic collaboration
- International collaboration
- Web of Science research areas
- Environmental Sciences
- Meteorology & Atmospheric Sciences