Monitoring of Sulphur Dioxide (SO2), Nitrogen Dioxide (NO2) and Carbon Monoxide (CO) in Trashigang Dzongkhag

Bhutan is experiencing significant growth in terms of industrial development, the construction of numerous motorable roads, and the expansion of automobile fleets. According to the Road Safety and Transport Authority of Bhutan, vehicle imports are increasing, and there were 125,982 registered vehicles in Bhutan as of 2023. Vehicle emissions are one of the major contributors to air pollution in Bhutan; therefore, it is crucial to monitor ambient air quality from time to time. In this study, the monitoring of sulfur dioxide, nitrogen dioxide, and carbon monoxide was carried out using low-cost sensors. Monitoring sites were selected based on population density, mixed areas, and sensitive areas. The three air pollutants were monitored over three different seasons: summer, winter, and spring. The average concentrations of sulfur dioxide, nitrogen dioxide, and carbon monoxide in Trashigang Dzongkhag for these three seasons were in the ranges of 0.01±0.01 – 0.04±0.03, 0.14±0.04 – 0.40±0.06, and 0.02±0.03 – 0.52±0.47 µg m-³, respectively. The findings of this study show that the concentrations of all the pollutants are below the permissible limits set by the National Environment Commission of Bhutan (NEC) and the World Health Organization (WHO) guidelines.