Cloud chemistry at the Puy de Dôme: variability and relationships with environmental factors

Abstract

Abstract. The chemical composition of cloud water was investigated during the winter-spring months of 2001 and 2002 at the Puy de Dôme station (1465 m above sea level, 45 • 46 22 N, 2 • 57 43 E) in an effort to characterize clouds in the continental free troposphere. Cloud droplets were sampled with single-stage cloud collectors (cut-off diameter approximately 7 µm) and analyzed for inorganic and organic ions, as well as total dissolved organic carbon. Results show a very large variability in chemical composition and total solute concentration of cloud droplets, ranging from a few mg l −1 to more than 150 mg l −1 . Samplings can be classified in three different categories with respect to their total ionic content and relative chemical composition: background continental (BG, total solute content lower than 18 mg l −1 ), anthropogenic continental (ANT, total solute content from 18 to 50 mg l −1 ), and special events (SpE, total solute content higher than 50 mg l −1 ). The relative chemical composition shows an increase in anthropogenic-derived species (NO We observed a high contribution of solute in cloud water derived from the dissolution of gas phase species in all cloud events. This was evident from large solute fractions of nitrate, ammonium and mono-carboxylic acids in cloud water, relative to their abundance in the aerosol phase. The comparison between droplet and aerosol composition clearly shows the limited ability of organic aerosols to act as cloud condensation nuclei. The strong contribution of gas-phase species limits the establishment of direct relationships between cloud water solute concentration and LWC that are expected from nucleation scavenging.

Tropospheric aerosol as a reactive intermediate

“…It should be realized, however, that (S/V) and total electrolyte concentrations of typical cloud and fog droplets and, hence, g will display wide variability over daily and weekly periods. 97 Thus, by adopting a representative average value for the uptake coefficient of NO 2 (g) on tropospheric aerosols: g $ 3 Â 10 À4 (see above), we estimate k d $ 6 Â 10 À5 s À1 , which corresponds to $20% NO 2 (g) hourly conversions in clear-day conditions, i.e., in the range of those observed in the eld. 26 By assuming that all HONO produced in reaction R1 is rapidly photolyzed via R6, the rate of _OH production at the terminus of this route, r +OH (R1), will therefore be given by eqn (E3):…”

Laboratory Study of Effects of Atmospheric Pollutants on Ice Nucleation Activity of Bacteria

“…The pH of the solutions has been selected to evaluate their impacts on the efficiency of bacterial INA (Attard et al, 2012). The anthropogenic activities can lead the cloud water to be pH 3.0 (Marinoni et al, 2004), which may require hundred times of the aforementioned normal concentrations of different solutions. Therefore, the concentrations of the solutions for the experiments of bacterial IN are normally set to be much higher than those of the in-situ observations (Attard et al, 2012).…”

“…Their results indicated that acidic pH has strong effects on the INA of Pseudomonus syringae, which can be highly reduced at the temperatures above -8°C. The anthropogenic activities can even result in the cloud water to be pH 3.0 (database available at http://www.obs.univbpclermont.fr/SO/beam/data.php), which is mainly attributed to ammonium sulfate, monocarboxylic acids (MCAs) and dicarboxylic acids (DCAs) (Marinoni et al, 2004). As dominant species of MCAs, formic and acetic acids have been found in the gas phase, aerosols cloud droplets and raindrops (Sun and Ariya, 2006).…”

Design and Validation of a Volatility Hygroscopic Tandem Differential Mobility Analyzer (VH-TDMA) to Characterize the Relationships Between the Thermal and Hygroscopic Properties of Atmospheric Aerosol Particles

“…• C. A primary candidate is HNO 3 that was found at elevated concentrations in both clouds and aerosols on the Puy de Dôme (Marinoni et al 2004;Sellegri et al 2003). Nitric acid is very volatile and is often found attached to the particle surface.…”