Seasonal variations of primary biological and biomass burning aerosols in the central Himalayas

Organic aerosols from biomass burning and primary biological sources are ubiquitous in the Earth's atmosphere. These aerosols have a significant impact on the absorption and scattering of solar radiation, serve as cloud condensation nuclei (CCN), and potentially influence the albedo of ice and snow in remote regions. Here we investigated polar organic markers for biomass burning, and primary biological aerosols at a remote site (Qomolangma, 4,276 m a.s.l.) of Mt. Everest, central Himalayas using a solvent extraction-BSTFA derivatization-GC/MS technique. Our results reveal distinct seasonal trends for biomass-burning aerosol tracers, exhibiting peak concentrations during the pre-monsoon season and reaching minimum levels during the summer monsoon period (579 and 49.1 ng C m−3 as organic carbon, respectively), which aligns with the patterns observed for aerosol organic carbon. Interestingly, fungal spore tracers and plant debris concentrations peak during both the pre-monsoon and post-monsoon seasons (sum of 40.8 and 38.7 ng C m−3 as organic carbon, respectively), indicating that primary bioaerosols and plant emissions are significant contributors to organic aerosols over the Tibetan Plateau in the post-monsoon period. Given primary bioaerosols' role as CCN and ice nuclei, and biomass burning's impact on light-absorbing aerosols, our findings are significant for understanding and addressing climate change in the Tibetan Plateau, known as the Earth's "Third Pole".