Study on the characteristic emission loading from the public transport and its contribution for air quality degradation over the Kathmandu valley : Grided emission estimation and dispersion modeling
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Department of physics
Abstract
The Kathmandu valley is witnessing an extremely poor air quality from years. The degradation of
air quality over Kathmandu is often found to be associated with the spontaneous urbanization,
haphazard industrial expansions and vehicular fleet. Present study was conceived to understand the
contribution of transport sector in degrading the air quality of Kathmandu valley. We developed a
comprehensive gridded emission inventories of potential pollutants and performed particulate
pollutant dispersion modelling using a comprehensive Chemical Transport Modelling (CTM) at the
horizontal grid resolution of 1 km
2
over an area of 70 km x 70 km that covers the Kathmandu valley
and its immediate surroundings, initialized with the Weather Research and Forecasting (WRF)
simulated meteorological fields.
The gridded emission inventory showed about 1918.17 kg km
−2
of TSP, 12872.74 kg km
−2
of CO,
6925.82 kg km
−2
of NOx
and 708.41 kg km
−2
of SO2
are currently loaded into the atmosphere of the
valley per day from the public transport over the Kathmandu valley. CTM simulation shows the
ambient concentration of PM2.5
due to public transport fleets appears a minimum during the day time
and remains maximum during the night and morning times. The pollutants released over the valley
are transported to the east and are flushed out into the eastern neighbouring valley. The contribution
of the public transport fleet to the deterioration of ambient air quality of the valley appears significant
compared to total emission from transport sector.