Atmos. Chem. Phys., 18, 1203–1216, 2018 https://doi.org/10.5194/acp-18-1203-2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 3.0 License. Transport of regional pollutants through a remote trans-Himalayan valley in Nepal Shradda Dhungel1, Bhogendra Kathayat2, Khadak Mahata3, and Arnico Panday1,4 1Department of Environmental Sciences, University of Virginia, Charlottesville, VA22904, USA 2Nepal Wireless, Shanti Marg, Pokhara, 33700, Nepal 3Institute for Advanced Sustainability Studies, 14467 Potsdam, Germany 4International Center for Integrated Mountain Development, Khulmaltar, Kathmandu, 44700, Nepal Correspondence: Shradda Dhungel (
[email protected]) Received: 16 September 2016 – Discussion started: 8 November 2016 Revised: 18 November 2017 – Accepted: 20 December 2017 – Published: 30 January 2018 Abstract. Anthropogenic emissions from the combustion of days to a week during non-monsoon months. Our observa- fossil fuels and biomass in Asia have increased in recent tions of increases in BC concentration and fluxes in the val- years. High concentrations of reactive trace gases and light- ley, particularly during pre-monsoon, provide evidence that absorbing and light-scattering particles from these sources trans-Himalayan valleys are important conduits for transport form persistent haze layers, also known as atmospheric of pollutants from the IGP to the higher Himalaya. brown clouds, over the Indo–Gangetic plains (IGP) from De- cember through early June. Models and satellite imagery suggest that strong wind systems within deep Himalayan valleys are major pathways by which pollutants from the 1 Introduction IGP are transported to the higher Himalaya. However, ob- servational evidence of the transport of polluted air masses Persistent atmospheric haze, often referred to as atmospheric through Himalayan valleys has been lacking to date.