Ground level ozone concentrations and its association with NO_x and meteorological parameters in Kathmandu valley, Nepal

摘要

This paper summarizes the results of a yearlong continuous measurements of gaseous pollutants, NO, NO_2, NO_x and O_3 in the ambient air at Kathmandu valley. Measured concentration of the pollutants in study area is a function of time. NO, NO_2 and O_3 peak occurred in succession in presence of sunlight. At the time of maximum O_3 concentration most of the NO_x are utilized. The diurnal cycle of ground level ozone concentrations, revealed mid-day peak with lower nocturnal concentrations and inverse relationship exists between O_3 and NO_x, which are evidences of photochemical O_3 formation. The observed ground level ozone during monsoon is slight lower than the pre-monsoon value. Further, lack of rainfall and higher temperature, solar radiation in the pre-monsoon have given rise to the gradual build up of ozone and it is lowest during winter. Ground level ozone concentrations measured during bandha (general strike) and weekend are 19% and 13% higher than those measured during weekdays. The most effective ozone abatement strategy for Kathmandu Valley may be control of NO_x emissions.