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Discussion papers | Copyright
https://doi.org/10.5194/acp-2018-599
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 15 Aug 2018

Research article | 15 Aug 2018

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

Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE): Emissions of particulate matter and sulfur dioxide from vehicles and brick kilns and their impacts on air quality in the Kathmandu Valley, Nepal

Min Zhong1,a, Eri Saikawa1,2, Alexander Avramov1, Chen Chen1, Boya Sun1, Wenlu Ye2, William C. Keene3, Robert J. Yokelson4, Thilina Jayarathne5,b, Elizabeth A. Stone5, Maheswar Rupakheti6, and Arnico K. Panday7 Min Zhong et al.
  • 1Department of Environmental Sciences, Emory University, Atlanta, GA, USA
  • 2Rollins School of Public Health, Emory University, Atlanta, GA, USA
  • 3Department of Environmental Sciences, University of Virginia, Charlottesville, VA, USA
  • 4Department of Chemistry, University of Montana, Missoula, MT, USA
  • 5Department of Chemistry, University of Iowa, Iowa City, IA, USA
  • 6Institute for Advanced Sustainability Studies, Potsdam, Germany
  • 7International Centre for Integrated Mountain Development (ICIMOD), Khumaltar, Nepal
  • anow at: Department of Environmental Engineering, Texas AM University-Kingsville, Kingsville, TX, USA
  • bnow at: Department of Chemistry, Purdue University, West Lafayette, IN, USA

Abstract. Air pollution is one of the most pressing environmental issues in the Kathmandu Valley, where the capital city of Nepal is located. We estimated emissions from two of the major source types in the valley (vehicles and brick kilns) and analyzed the corresponding impacts on regional air quality. First, we estimated the on-road vehicle emissions in the valley using the International Vehicle Emission (IVE) model with local emission factors and the latest available data for vehicle registration. We also identified the locations of the brick kilns in the Kathmandu Valley and developed an emissions inventory for these kilns using emission factors measured during the Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE) field campaign in April 2015. Our results indicate that the commonly-used global emissions inventory, the Hemispheric Transport of Air Pollution (HTAP_v2.2), underestimates particulate matter emissions from vehicles in the Kathmandu Valley by a factor greater than 100. In addition, brick kilns account for nearly 70% of total sulfur dioxide (SO2) emissions from all sectors considered in HTAP_v2.2. Next, we simulated air quality using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) for April 2015 based on three different emission scenarios: HTAP only, HTAP with updated vehicle emissions, and HTAP with both updated vehicle and brick kilns emissions. Comparisons between simulated results and observations indicate that the model underestimates observed surface elemental carbon (EC) and SO2 concentrations under all emissions scenarios. However, our updated estimates of vehicle emissions significantly reduced model bias for EC, while updated emissions from brick kilns improved model performance in simulating SO2. These results highlight the importance of improving local emissions estimates for air quality modeling. We further find that model overestimation of surface wind leads to underestimated air pollutant concentrations in the Kathmandu Valley. Future work should focus on improving local emissions estimates for other major and underrepresented sources (e.g., crop residue burning and garbage burning) with a high spatial resolution, as well as the model's boundary-layer representation, to capture strong spatial gradients of air pollutant concentrations.

Min Zhong et al.
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Short summary
Air pollution is one of the most pressing environmental issues in the Kathmandu Valley, the capital city of Nepal. We estimated emissions from two of the major source types in the valley (vehicles and brick kilns) and found that they have significant impacts on air quality surrounding the Valley. Our results highlight the importance of improving local emissions estimates for air quality modeling.
Air pollution is one of the most pressing environmental issues in the Kathmandu Valley, the...
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