A fine fraction of soil used as an aerosol analogue during the DUNE experiment: sequential solubility in water, decreasing pH step-by-step
- 1Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), UMR7583 CNRS-INSU, University Paris 7 Denis Diderot, University Paris-Est Créteil, France
- 2Laboratoire des Sciences du Climat et de l'Environnement (LSCE), UMR8212 CEA-CNRS-UVSQ-CEA Saclay 701, 91191 Gif-sur-Yvette CEDEX France
- *now at: Institut de Physique du Globe de Paris (IPGP), Sorbonne Paris Cité, University Paris 7 Denis Diderot, UMR7154 CNRS, 75005 Paris, France
Abstract. A soil sample collected in a desert aerosol source area near Douz (southern Tunisia) was dry-sieved at 20 μm in order to extract the fraction similar to a wind-generated aerosol, and was used to seed mesocosms during the DUNE experiment (a DUst experiment in a low Nutrient, low chlorophyll Ecosystem). In this work, said "aerosol-like" fine dust was sequentially leached by short contacts with water at initial pHs, decreasing from seven to one, representing various wet environmental conditions. For each step, the solubility of a given element is calculated as the amount of its dissolved fraction, relative to its total amount. The evolution of this fractional solubility from the highest to lowest pHs provides information on the chemical strength needed to solubilise a given element and its lability. The behaviour of the elemental solubility was sorted into two groups: (1) Ca, Sr, Ba, Mn, and P, with a solubility between 23% and 70%, and a maximum sequential solubility at pH 3; (2) Al and Fe, with a solubility of less than 2% and 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.