Cloud condensation nuclei activation properties of Mediterranean pollen types considering organic chemical composition and surface tension effects
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AuthorCasans Gabasa, Andrea; Rejano Martínez, Fernando; Maldonado Valderrama, Julia; Casquero Vera, Juan Andrés; Ruiz Peñuela, Soledad; Lyamani, H.; Cazorla Cabrera, Alberto; Pérez Ramírez, Daniel; Olmo Reyes, Francisco José; Alados Arboledas, Lucas; Cariñanos González, Paloma; Titos Vela, Gloria
AerosolPollenCloud condensation nucleiHygroscopicitySurface tension
A. Casans et al. Cloud condensation nuclei activation properties of Mediterranean pollen types considering organic chemical composition and surface tension effects. Atmospheric Environment 310 (2023) 119961 [https://doi.org/10.1016/j.atmosenv.2023.119961]
SponsorshipBioCloud project (RTI2018.101154.A. I00) funded by MCIN/AEI/10.13039/501100011033, FEDER “Una manera de hacer Europa” and NUCLEUS project (PID2021-128757OB- I00) funded by MCIN/AEI/10.13039/501100011033; NextGenerationEU/PRTR; European Union’s Horizon 2020 research and innovation program through projects ACT- RIS.IMP (grant agreement No 871115); European Union’s Horizon 2020 research and innovation program through project ATMO_ACCESS (grant agreement No 101008004; Spanish Ministry of Science and Innovation through projects ELPIS (PID2020-120015RB-I00) and ACT-RIS-España (CGL2017-90884REDT); Junta de Andalucía Excel- lence, project ADPANE (P20-00136), AEROPRE (P-18-RT-3820); University of Granada Plan Propio through Visiting Scholars (PPVS2018-04), Singular Laboratory (LS2022-1) programs and Pre- Competitive Research Projects Pre-Greenmitigation3 (PP2022.PP34); Funding for open access charge, University of Granada/CBUA; Spanish ministry of research and innovation under the predoctoral program FPI (PRE2019-090827) funded by MCIN/AEI/ 10.13039/501100011033; Spanish ministry of universities through predoctoral grant FPU19/05340; FJC2021- 047873-I, MCIN/AEI/10.13039/501100011033 and NextGenerationEU/PRTR; NOAA cooperative agreements NA17OAR4320101
Wind-dispersed pollen grains emitted from vegetation are directly injected into the atmosphere being an important source of natural aerosols globally. These coarse particles of pollen can rupture into smaller particles, known as subpollen particles (SPPs), that may act as cloud condensation nuclei (CCN) and affect the climate. In this study, we characterize and investigate the ability of SPPs of 10 Mediterranean-climate pollen types to activate as CCN. A continuous flow CCN counter (CCNC) was used to measure the activation of size-selected (80, 100 and 200 nm dry mobility diameter) particles at different supersaturations (SS). Hygroscopicity parameter (κ) for each SPP type and size has been calculated using κ-K¨ohler theory. Organic chemical speciation and protein content has been determined to further characterize pollen solutions. Furthermore, the surface activity of SPPs has also been investigated by using pendant drop tensiometry. All studied SPP samples show critical supersat- uration (SSCrit) values that are atmospherically relevant SS conditions. Hygroscopicity κ values are in the range characteristic of organic compounds (0.1–0.3). We found that organic speciation and protein content vary substantially among pollen types, with saccharides and fatty acids being the only organic compounds found in all pollen types. A clear relationship between SPP activation and its organic composition was not observed. This study also reveals that all SPPs investigated reduce the surface tension of water at high concentrations but at diluted concentrations (such as those of activation in the CCNC), the water surface tension value is a good approximation in K¨ohler theory. Overall, this analysis points out that pollen particles might be an important source of CCN in the atmosphere and should be considered in aerosol-cloud interactions processes.