Speciation of Inorganic Sulphur in Aquifer Sediments Contaminated by Landfill Leachate Using Chemical Extraction Techniques

Author： Crouzet C.

Publisher： Taylor & Francis Ltd

ISSN： 0959-3330

Source： Environmental Technology, Vol.21, Iss.3, 2000-03, pp. : 285-296

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Abstract

A protocol for determining the distribution of sulphur forms in aquifer solids is proposed. A series of single parallel extractions and of two-step treatments, derived from a combination of previously described extractions are tested on simple Fe and/or S minerals (goethite, alkageneite, hematite, ferrous sulphide, pyrite, flower elemental sulphur and ferrous sulphate). Monosulphides are extracted with hot HCl. Iron disulphides are determined using a Cr(II) digestion after preliminary elimination of monosulphides, elemental sulphur and sulphates with HI. Sulphate is extracted by NaH₂PO₄ followed by HI treatment. Elemental sulphur is estimated from differences between total sulphur and the fractions quantified above. The method is applied to reduced and oxidised sediments from a well-characterised sandy aquifer system downgradient from the Danish Vejen landfill. Total inorganic sulphur decreases rapidly when moving away from the landfill. Sulphidic phases are dominant in the most reduced sediment. Iron disulphide is found in the moderately reduced sediments (iron reducing conditions). Oxygenated sulphur is significant in the most oxidised samples. Several discrepancies between water composition and sulphur forms in the solids are explained by non-equilibrium conditions.