Trace Metals in Cloud Water Sampled at the Puy De Dôme Station

Abstract

Concentrations of 33 metal elements were determined by ICP-MS (Inductively CoupledPlasma Mass Spectrometry) analysis for 24 cloud water samples (corresponding to 10 cloud events) collected at the puy de Dôme station. Clouds present contrasted chemical composition with mainly marine and continental characteristics; for some cloud events, a further anthropogenic source can be superimposed on the background level. In this context, measurements of trace metals may help to evaluate the impact of anthropogenic and natural sources on the cloud and to better discriminate the origin of the air masses. The metal concentrations in the samples are low (between 16.4 µg L −1 and 1.46 mg L −1 ). This could be explained by the remoteness of the puy de Dôme site from local sources. Trace metals are then used to confirm and refine a previous sample classification. A principal component analysis (PCA) using the pH value and the concentrations of Cl − , NO 3 − , SO 4 2− , Na + and NH 4 + is performed considering 24 cloud samples. This first analysis shows that 18 samples are of marine origin and 6 samples are classified as continental. The same statistical approach is used adding trace metal concentration. Zn and Mg elements are the most abundant trace metals for all clouds. A higher concentration of Cd is mainly associated to clouds from marine origins. Cu, As, Tl and Sb elements are rather found in the continental samples than in the marine ones. Mg, V, Mn and Rb elements mainly found in soil particles are also more concentrated in the samples from continental air mass. This new PCA including trace metal confirms the classification between marine and continental air masses but also indicates that one sample presenting low pH and high concentrations of SO 4 2− , Fe, Pb and Cu could be rather attributed to a polluted event.

The acidity of atmospheric particles and clouds

“…In terrestrial ecosystems, direct effects of acid deposition to foliage include leaching of cations, altered stomatal function, and changes in wax structure (Cape, 1993). Acid deposition can exacerbate soil acidification (Binkley and Richter, 1987), resulting in loss of soil base cations, leaching of nitrate, and mobilization of aluminum, affecting terrestrial ecosystem health and the quality of water delivered to streams and lakes (Driscoll et al, 2007). Apart from reactive nitrogen, atmospheric deposition is also a significant source of limiting and trace nutrients such as phosphorus (P), iron (Fe), and copper (Cu), especially in the remote oceans (Mahowald et al, 2008;Myriokefalitakis et al, 2018).…”

Photochemistry of the Cloud Aqueous Phase: A Review

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

“…In cloud droplets, the speciation of iron between its two oxidation states (II and III) is a key parameter of its reactivity in solution and is a function of pH and redox potential, as shown in Figure 3b. concentration is ~10 −6 M, but many field experiments indicate that it can vary from 10 −9 to 10 −6 M in raindrops and cloud droplets [28,39,40,43,118,119]. The concentration of iron drives the concentration of radicals in cloud droplets, but also partly in the gaseous phase (due to the rate of the mass transfer).…”

Cézeaux-Aulnat-Opme-Puy De Dôme: a multi-site for the long term survey of the tropospheric composition and climate change

“…Inductively Coupled Plasma Mass Spectrometry (ICP-MS) (Bianco et al, 2017). The oxidative capacity of the cloud water has also been evaluated following the hydroxyl radical (HO • ) formation rates during the irradiation of cloud waters under sun-simulated radiation (Bianco et al, 2015).…”