Measurement report: Increasing trend of atmospheric ion concentrations in the boreal forest

Abstract. The concentration of atmospheric ions affects the total aerosol particle number concentrations in atmosphere as well new formation via ion-induced nucleation, ion–ion recombination, and effects on condensational growth. In this study, we investigate long-term trends a boreal forest environment using 16 years cluster ion (0.8–2 nm) intermediate (2–7 measurements characterize most important factors that explain those trends. We found median was 710 cm−3, 2–4 14 4–7 nm 9 cm−3. both have been increasing over 16-year measurement period, with by about 1 % yr−1 1.7 %–3.9 yr−1. increase can be best explained decrease coagulation sink caused larger particles. Meanwhile, dependence meteorological conditions is evident, but ionization sources do not seem to trend. This likely because dynamics are more complicated, so alone cannot directly variation. Season-specific analysis suggests while limiting factor for spring summer, different autumn winter. Based our findings, recommend comprehensive needed determine if ambient concentrations, temperature, changing abundance condensable vapors makes ion-mediated nucleation pathways relevant future.