Seasonal Variation in Ambient Air Pollutants and Influence of Meteorological Factors in an Urban Environment, Sri Lanka
BUDDHI PUSHPAWELA, Sherly Shelton, Gayathri Liyanage, Sanduni Jayasekara, Akila Jayasundara, LestyDias Jayasuriya,
California Institute of Technology Abstract Number: 375
Working Group: Urban Aerosols
AbstractThe deterioration of air quality indoors and outdoors is a significant public health problem in Sri Lanka. Few studies have investigated the effects of ambient air pollutants on human health. To the best of the author's knowledge, the seasonal variability of ambient air pollutants has not been previously reported.
The study aimed to provide a broader perspective on the seasonal variation of CO, NO
2, SO
2, O
3, PM
2.5, and PM
10 and possible relationship between air pollution and meteorological factors in two cities in Sri Lanka. The data were obtained from ambient air quality monitoring stations at Colombo and Kandy from 2018 to 2021, excluding the COVID-19 lockdown. The analysis was based on four seasons; Southwest monsoon (SWM; June-September), Northeast monsoon (NEM; December-February), first inter-monsoon (FIM; March-May), and second inter-monsoon (SIM; October-November) period. The results showed that the diurnal variation of measured pollutants except for O
3 for all seasons followed a similar bimodal distribution pattern in both cities. We observed the hourly average concentrations of pollutants reach their maximum during the morning (6-8 am) and the evening (6-8 pm) hours, irrespective of the seasons. This observed morning and evening peaks coincided well with the morning and evening rush hour traffic.
The results showed a considerable seasonal variation in the concentration of all pollutants. The minimum and maximum daytime pollutant concentrations in Colombo are recorded in the SWM and NEM seasons. In Kandy, the maximum daytime concentration of O
3, NO
2, PM
2.5, and PM
10 are recorded for the FIM season, while CO and SO
2, are recorded at maximum concentration during the SWM season. We found that wind speed and direction is the most influencing factor for pollutant concentration for all seasons. The findings help understand seasonal variation in ambient air quality, which contributes to formulating season-specific control measures to improve regional air quality.