Dynamics of PM2.5 concentrations in Kathmandu valley

Publisher:
Elsevier Science Bv
Publication Type:
Journal Article
Citation:
Journal of Hazardous Materials, 2009, 168 (2-3), pp. 732 - 738
Issue Date:
2009-01
Full metadata record
Files in This Item:
Filename Description Size
Thumbnail2008005323OK.pdf1.07 MB
Adobe PDF
This study analysed daily patterns and dynamics of PM2.5 concentrations in the Kathmandu Valley during three winters. The PM2.5 data showed a daily repetitive cycle which represents influence of local air flow and dispersion and accumulation of air pollutants in the valley. Two concentration peaks were observed in the morning and in the evening periods, and they fell down during the daytime and the nighttime periods. This indicates local emission sources as major contributors in the valley. The more pronounced morning peak compared to the evening peak showed that the upslope wind in the morning helped to move the polluted inversion layer downward, subsequently adding to freshly emitted pollutants and causing a sharp pollutant concentration rise in the morning. Katabatic wind and rise of temperature in the basin during the day helped the pollutant upflow and dilution, resulting in a sharp PM2.5 concentration decline. Through the afternoon, the decrease in air temperature followed by decrease in wind speed caused to lower PM2.5 peaks in the evening. Also. higher morning peaks of PM2.5 concentrations compared to the evening indicated pollution from the previous day is added to the fresh emission. The valley had increased PM2.5 from the beginning of October which continued till the first week of February. The increase in PM2.5 peak fit the logistic equation y = [k/(1 + exp (p - qx)] + a sin(bx) where k, p, q, a, and b are constants.
Please use this identifier to cite or link to this item: