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Quantification and source apportionment of brown carbon aerosols in the high Himalayas (HIMALAYABROWNCARBON)
Date du début: 3 juin 2014, Date de fin: 2 juin 2016 PROJET  TERMINÉ 

The high Himalayan glaciers that provide the water supply of large Indian rivers are significantly affected by anthropogenic climate warming. The light-absorbing aerosols participate in the Himalayan glaciers’ retreat processes not only via their contribution to climate warming, but also due to reduction of the albedo of the glaciers and weakening of the South Asian monsoon that feeds the glaciers. Several recent observational and modeling studies showed the light-absorbing organic aerosols – “brown carbon” (BrC) to be an important climate forcing agent in South Asian region. Aerosol BrC can be emitted directly in the combustion processes and formed by the chemical reactions in the atmosphere, it can accumulate over time, and increase its importance when traveling from near-source sites to remote locations. The high Himalayan region is exposed to photochemically aged air with the highly modified chemical composition of aerosols compared to the pollution source regions and the contribution from different sources to BrC at this high altitude environment is still poorly understood. This project is intended to assist society in targeting efficient mitigation of the Himalayan glaciers retreat through the determination of the composition and main sources of BrC in the area. This research project combines on-line (continues monitoring) data and off-line chemical analysis of aerosol filter samples collected at the Nepal Climate Observatory-Pyramid (NCO-P) (5079 m a.s.l.). Advanced analytical techniques (e.g., ion and liquid chromatography, spectrophotometry, NMR) for measurements of organic carbon and nitrogen and organic tracers allow to elaborate the resulting dataset using factor analysis in order to determine and quantify the primary and secondary components of BrC. Understanding of sources and formation pathways would allow to control the emissions of BrC and its precursors leading to a slowdown of the Himalayan glacier loss.