Chemical composition and droplet size distribution of cloud at the summit of Mount Tai, China

Abstract

Abstract. The chemical composition of 39 cloud samples and droplet size distributions in 24 cloud events were investigated at the summit of Mt. Tai from July to October 2014. Inorganic ions, organic acids, metals, HCHO, H 2 O 2 , sulfur(IV), organic carbon, and elemental carbon as well as pH and electrical conductivity were analyzed. The acidity of the cloud water significantly decreased from a reported value of pH 3.86 during (Guo et al., 2012 to pH 5.87 in the present study. The concentrations of nitrate and ammonium were both increased since 2007-2008, but the overcompensation of ammonium led to an increase in the mean pH value. The microphysical properties showed that cloud droplets were smaller than 26.0 µm and most were in the range of 6.0-9.0 µm at Mt. Tai. The maximum droplet number concentration (N d ) was associated with a droplet size of 7.0 µm. High liquid water content (LWC) values could facilitate the formation of larger cloud droplets and broadened the droplet size distribution. Cloud droplets exhibited a strong interaction with atmospheric aerosols. Higher PM 2.5 levels resulted in higher concentrations of water-soluble ions and smaller sizes with increased numbers of cloud droplets. The lower pH values were likely to occur at higher PM 2.5 concentrations. Clouds were an important sink for soluble materials in the atmosphere. The dilution effect of cloud water should be considered when estimating concentrations of soluble components in the cloud phase.

The Impact of Changes in Cloud Water pH on Aerosol Radiative Forcing

“…These regional differences in the temporal response of the sulfate mass burden reflect the relative changes in anthropogenic emissions of SO 2 : decreases in emissions over Europe and United States but an increase over China. However, temporal changes in other emissions (e.g., NH 3 ) could also have an important effect on pH and aerosols (Li et al, ; Weber et al, ). Aqueous phase sulfate formation across polluted continental regions is sensitive to changes in cloud water pH, particularly in winter, due to larger SO 2 concentrations and strong seasonal limitation in oxidants at higher latitudes (Manktelow et al, ).…”

Photochemistry of the Cloud Aqueous Phase: A Review

“…The main chemical species in cloud water are inorganic ions (such as Cl − , Na + , SO 4 2− , NO 3 − , NH 4 + , etc.) [14,24,[30][31][32][33][34][35][36][37][38], transition metals (Fe, Cu, Mn, . .…”

“…. ) [26,[38][39][40][41][42][43], and organic compounds (carboxylic acids, aldehydes, amino acids, . .…”

H<sub>2</sub>O<sub>2</sub> modulates the energetic metabolism of the cloud microbiome

“…In this liquid phase, it is also produced by aqueous-phase reactivity (Möller, 2009). Several field campaigns have reported H 2 O 2 concentrations in atmospheric water in the µM range (Gunz and Hoffmann, 1990;Marinoni et al, 2011;Deguillaume et al, 2014;Li et al, 2017). Hydrogen peroxide plays a central role in various important chemical processes in clouds.…”