A thesis submitted in the partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources & Development

Thesis (M.Eng.) - Asian Institute of Technology, 1994

As visibility is directly related to air pollution, visibility data were analyzed for the period of 1975-1993 in light of meteorological factors to detect the air quality trend in Kathmandu Valley. It can be concluded that the visibility in Kathmandu Valley is deteriorating most likely due to man made activities i.e air pollution emissions. Meteorological influence on annual visibility trend are not paramount. Detailed emission inventory as a function of time and space has also been made for 1992/93 to estimate the contribution of different sources on air quality deterioration in the valley. Fuelwood/biomass combustion for Total Suspended Particulate (TSP) and Carbon monoxide (CO), automobiles for Nitrogen Oxides (NOJ and Hydrocarbons (HC), and coal combustion in brick and cement industries for Sulfur Dioxide (S02) are the major sources of emission. Estimation of emission for past year (1984/85) and a future year (2002/03) were also made. It shows that per capita emission of TSP is decreasing whereas Nitrogen Oxides (NOx) and Sulfur Dioxide (S02) are increasing considerably. Annual visibility trend shows strong negative correlation with air pollution emissions, specially Sulfur Dioxide (S02) and Nitrogen Oxides (NOJ. Among the visibility reducing species, sulfate and nitrate particle are expected to be the major contributor in the visibility change in the valley and the particulate concentration in Kathmandu Valley might exceed WHO standard most of the time in recent years. Much higher particulate concentration can be expected in urban centers. As the air quality of the valley is deteriorating rapidly, it is an urgent need to establish emission regulations and control strategies. This study provides an input to the modelling work, an important tool for air quality management, and source reduction strategies. Since actual measurement of air pollution concentration are unavailable, this type of study is appropriate to detect the air quality trend and to estimate sources contribution in most of the cities of the developing countries.