Variability of Anthropogenic Gases: Nitrogen Oxides, Sulfur Dioxide, Ozone and Ammonia in Kathmandu Valley, Nepal

Ground-level ozone (O₃) poses significant air quality concerns in the Kathmandu Valley, frequently exceeding health guidelines. A 2013 study revealed higher O₃ concentrations in rural areas (108.5 ± 31.4 μg m⁻³) compared to urban sites (87.1 ± 9.2 μg m⁻³), highlighting the role of meteorology and precursor gases in its formation. Urban regions also exhibited elevated nitrogen dioxide (NO₂, 22.4 ± 8.1 μg m⁻³) and sulfur dioxide (SO₂, 14.5 ± 11.1 μg m⁻³) levels, with SO₂ peaking near brick factories (22.3 ± 14.7 μg m⁻³). Ammonia (NH₃) emerged as a critical pollutant near polluted rivers, while SO₂’s proximity to industrial sources underscored its role in particulate matter formation. The study employed passive sampling across 15 sites from March to May 2013, followed by targeted measurements in 2014, revealing spatial variability and the need for intensified monitoring.

Kiros, F., Shakya, K. M., Rupakheti, M., Regmi, R. P., Maharjan, R., Byanju, R. M., Naja, M., Mahata, K., Kathayat, B., & Peltier, R. E. (2016). Variability of Anthropogenic Gases: Nitrogen Oxides, Sulfur Dioxide, Ozone and Ammonia in Kathmandu Valley, Nepal. Aerosol and Air Quality Research, 16(12), 3088–3101. https://doi.org/10.4209/aaqr.2015.07.0445