Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 5.668 IF 5.668
  • IF 5-year value: 6.201 IF 5-year
  • CiteScore value: 6.13 CiteScore
  • SNIP value: 1.633 SNIP 1.633
  • IPP value: 5.91 IPP 5.91
  • SJR value: 2.938 SJR 2.938
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 174 Scimago H
    index 174
  • h5-index value: 87 h5-index 87
Discussion papers
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 08 May 2019

Submitted as: research article | 08 May 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).

Ambient air quality in the Kathmandu Valley, Nepal during the pre-monsoon: Concentrations and sources of particulate matter and trace gases

Md. Robiul Islam1, Thilina Jayarathne1,a, Isobel J. Simpson2, Benjamin Werden3, John Maben4, Ashley Gilbert1, Puppala S. Praveen5, Sagar Adhikari5,6, Arnico K. Panday5, Maheswar Rupakheti7, Donald R. Blake2, Robert J. Yokelson8, Peter F. DeCarlo3,9, William C. Keene4, and Elizabeth A. Stone1,10 Md. Robiul Islam et al.
  • 1University of Iowa, Department of Chemistry, Iowa City, IA, USA
  • 2University of California-Irvine, Department of Chemistry, Irvine, CA, USA
  • 3Drexel University, Department of Civil, Architectural, and Environmental Engineering, Philadelphia, PA, USA
  • 4University of Virginia, Department of Environmental Sciences, Charlottesville, VA, USA
  • 5International Centre for Integrated Mountain Development (ICIMOD), Lalitpur, Nepal
  • 6MinErgy Pvt. Ltd, Lalitpur, Nepal
  • 7Institute for Advanced Sustainability Studies, Potsdam, Germany
  • 8Department of Chemistry, University of Montana, Missoula, MT, USA
  • 9Drexel University, Department of Chemistry, Philadelphia, PA, USA
  • 10Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, IA, USA
  • anow at: Purdue University, Department of Chemistry, West Lafayette, IN, USA

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 (NAMaSTE), ambient air quality in the Kathmandu Valley was investigated from 11 to 24 April 2015, during the pre-monsoon season. Ambient concentrations of fine and coarse particulate matter (PM2.5 and PM10, respectively), online PM1, inorganic trace gases (NH3, HNO3, SO2, and HCl), and carbon-containing gases (CO2, CO, CH4, and 85 non-methane volatile organic compounds; NMVOC) were quantified at a semi-urban location near the center of the valley. Concentrations and ratios of NMVOC indicated that origins primarily from poorly-maintained vehicle emissions, biomass burning, and solvent/gasoline evaporation. During those two weeks, daily average PM2.5 concentrations ranged from 30 to 207 µg m−3, which exceeded the World Health Organization 24 hour guideline by factors of 1.2 to 8.3. On average, the non-water 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 HCl, 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 (1230 ± 1153 ng m−3), 1,3,5-triphenylbenzene (0.8 ±0.5 ng m−3), cholesterol (3.0 ± 6.7 ng m−3), stigmastanol (1.4 ± 6.7 ng m−3), and cis-pinonic acid (4.5 ± 0.6 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 NAMaSTE, 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 two of previous estimates, but relatively 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 for 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) 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.

Md. Robiul Islam et al.
Interactive discussion
Status: open (extended)
Status: open (extended)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
[Subscribe to comment alert] Printer-friendly Version - Printer-friendly version Supplement - Supplement
Md. Robiul Islam et al.
Md. Robiul Islam et al.
Total article views: 463 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
346 111 6 463 24 3 4
  • HTML: 346
  • PDF: 111
  • XML: 6
  • Total: 463
  • Supplement: 24
  • BibTeX: 3
  • EndNote: 4
Views and downloads (calculated since 08 May 2019)
Cumulative views and downloads (calculated since 08 May 2019)
Viewed (geographical distribution)  
Total article views: 408 (including HTML, PDF, and XML) Thereof 401 with geography defined and 7 with unknown origin.
Country # Views %
  • 1
No saved metrics found.
No discussed metrics found.
Latest update: 16 Sep 2019
Publications Copernicus
Short summary
The Kathmandu Valley experiences high levels of air pollution. In this study, atmospheric gases and particulate matter were characterized by online and off-line measurements, with an emphasis on understanding their sources. The major sources of particulate matter and trace gases were identified as garbage burning, biomass burning, and vehicles. The majority of secondary organic aerosol was attributed to anthropogenic precursors, while a minority was attributed to biogenic gases.
The Kathmandu Valley experiences high levels of air pollution. In this study, atmospheric gases...