Quantification and source apportionment of atmospheric trace gases over Dhaka, Bangladesh

Abstract

Five atmospheric trace gases were measured in Dhaka, Bangladesh, using an automated direct sensing gas monitoring system. The average concentrations of CO, NO, NO₂, TVOC, and O₃ were 2603.6 ± 1216.4, 281.5 ± 158.0, 182.7 ± 69.4, 10,068.2 ± 5296.1 and 36.6 ± 23.6 µg/m³. The measured trace gas concentrations demonstrated significant seasonal and monthly fluctuations, with NO and CO concentrations being the highest in winter, O₃ and TVOC concentrations being the highest during the monsoon season, and NO₂ concentrations being the highest during the pre-monsoon season. Air mass trajectories and wind rose plots during the monsoon were compared to the winter. It showed that air masses from the southeast and south had an impact on the quantity of most of the trace gases whilst they traveled over the Bay of Bengal throughout the monsoon period. In contrast, air masses from the northwestern region, north, and the west had a bigger effect on the rising amount of trace gases across the Indo Gangetic Plain (IGP) during the winter season. NO₂ (182.7 µg/m³) had the maximum concentration of the gases measured and crossed the World Health Organization’s (WHO) annual recommended value. The source characteristics of NOx, TVCO, and O₃ gases were determined using the positive matrix factorization (PMF 5.0) model. The combustion of fossil fuels and aerosols were found to be the major sources of NOx and O₃, with aerosol formation being the primary source of TVOC concentration.