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

[摘要] A soil sample collected in a desert aerosol source area near Douz (southernTunisia) was dry-sieved at 20 μm in order to extract the fractionsimilar to a wind-generated aerosol, and was used to seed mesocosms duringthe DUNE experiment (a DUst experiment in a low Nutrient, low chlorophyll Ecosystem). In this work, said "aerosol-like" fine dust wassequentially leached by short contacts with water at initial pHs, decreasingfrom seven to one, representing various wet environmental conditions. Foreach step, the solubility of a given element is calculated as the amount ofits dissolved fraction, relative to its total amount. The evolution of thisfractional solubility from the highest to lowest pHs provides information onthe 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% and70%, and a maximum sequential solubility at pH 3; (2) Al and Fe, with a solubility of less than 2% and the highest releaseat pH 1. Similar solubility patterns in group 1 for Ca, P, and Mn suggest apossible association of the elements in the same minerals, most probablycarbonates.

[学科分类] 地球化学与岩石