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A fine fraction of soil used as an aerosol analogue during the DUNE experiment: sequential solubility in water with step-by-step decreasing pH

March 5, 2014

A soil sample collected in a desert aerosol source area near Douz (South Tunisia) was sieved at 20 µm in order to extract the fraction similar to an aerosol generated by wind and used to seed mesocosms during the DUNE experiment. In the present work, this “aerosol-like” fine dust was sequentially leached by short contacts with water at pHs decreasing from 7 to 1. These pHs are representative of various environmental wet conditions, the lowest of which could be reached during cloud conditions. The evolution of the solubility from the highest to the lowest pHs provides information on the necessary strength for the solubilisation of a given element and its lability. The behaviour of the elemental fractional solubility is sorted into two groups: (i) Ca, Sr, Ba, Mn, P constitute group 1, with a solubility between 23 % and 70 % and with a maximum solubility at pH 3; (ii) whereas in group 2 (Al, Fe), the solubility is less than 2 % with the highest release at pH 1. Similar solubility patterns in group 1 for Ca, P and Mn suggest a possible association of the elements in the same minerals, most probably carbonates, which gives phosphorus an unexpected high lability.

Aghnatios C, Losno R, Dulac F, 2014: A fine fraction of soil used as an aerosol analogue during the DUNE experiment: sequential solubility in water with step-by-step decreasing pH, Biogeosciences Discuss., 11, 2623-2637, doi: 10.5194/bgd-11-2623-2014. Article.

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