Author(s)

M. L. Shrestha, A. Kaga, A. Kondo, Y. Inoue & B. Sapkota

Abstract

Diurnal variation of air pollution concentration during winter in Kathmandu valley M. L. Shrestha1, A. Kaga1, A. Kondo1, Y. Inoue1 & B. Sapkota2 1Department of Environmental Engineering, Osaka University, Japan 2 Institute of Engineering, Pulchok Tibhuvan University, Nepal Abstract The air pollution concentration during the winter season in Kathmandu valley is high compare to the summer season. NO2 concentration and TSP concentration measurements were done on the roof of the Institute of Engineering, Tribhuvan University, Nepal in, February 2001. Simultaneously, temperature was measured at Raniban Mountain located in the north east of Kathmandu city at the height of 60m, 220m and 400m above the Institute of Engineering. The air pollution concentration of Kathmandu valley was seen to increase gradually after sunset and increased abruptly from early morning and reached the maximum value from 6 am to 9 am. After that, it showed an abrupt decrease and became the minimum value in the daytime. From nighttime till early morning, the temperature at the lower height (60m) was seen to be lower than the temperature at the higher height (400 m). It shows that strong inversion layer is formed in Kathmandu valley and the air pollution concentration in the valley is strongly influenced by the inversion layer.

Keywords