Measurement report: Chemical characterization of cloud water at Monte Cimone (Italy) – impact of air mass origin and assessment of atmospheric processes

Abstract. In this article, we present the results of the chemical and microbiological characterization of clouds water collected at Monte Cimone (CMN) in Italy at 2165 m a.s.l. during the MC3 (Molecular Composition of Clouds at mt. Cimone) campaign, which took place in October 2024. Twenty-six cloud samples are analyzed. Chemical analyses, including ions, oxidants, trace metals, and microbiological analyses with cell counting, are performed. The chemical characterization and back-trajectories analysis reveal that Mt. Cimone is a site under the influence of marine air masses, coming mainly from southern Europe and from the Mediterranean region. During the measurement campaign, 3 sampling periods are identified: period (1) 7–10 October, with air masses mainly originating from Spain and Atlantic Ocean with a majority of Cl− and Na+ that are characteristics of marine origin; period (2) 16–18 October with air masses originating from North of Africa, impacted by a Saharan dust event with a high concentration in Ca2+; period (3) 22–23 October marked by air masses originated from southern Italy under polluted influence with a high concentration in NO3-. Across the campaign, DOC ranged from 1.6 to 4.3 mgC L−1, while H2O2 reached its maximum during period 3 (71.8±35.4 µmol L−1), highlighting enhanced oxidant levels under polluted conditions. This study paves the way to further scientific campaigns intended to better comprehend cloud water composition at Mt. Cimone.