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Environmental fate & pathways

Hydrolysis

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Description of key information

SrS dissolves upon contact with water, releasing strontium and sulfide ions. An equilibrium establishes between S2-, HS-, and H2S as a function of pH, and the  Hägg graph (see IUCLID 5.1.2 "Hägg, 1969 - sulfides") provides key information. For strontium, hydrolysis is not a relevant endpoint.

Key value for chemical safety assessment

Additional information

Abiotic degradation is an irrelevant process for inorganic substances that are assessed on an elemental basis, including strontium sulfide. In the aqueous environment, strontium sulfide dissolves in water releasing strontium cations and sulfide anions (see physical and chemical properties).

Sulfide anions react with water in a pH-dependant reverse dissociation to form bisulfide (HS-) or hydrogen sulfide (H2S), respectively (i.e., increasing H2S formation with decreasing pH). Thus, sulfide (S2-), bisulfide (HS-) and hydrogen sulfide (H2S) coexist in aqueous solution in a dynamic pH-dependant equilibrium. In oxic systems, oxidation to - eventually - sulfate occurs.

Strontium exists almost exclusively in the environment as Sr+2cation and will form hydrated cation, SrOH+, strontium sulfate, SrSO4(celestite), and strontium carbonate, SrCO3(strontianite). Celestite and strontianite are the two common strontium minerals in nature and there are not very soluble in water: 125 mg/L (at 25 °C) for strontium sulfate and ~ 10 mg/L (at 25 °C) for strontium carbonate (IUCLID, 2014 and IUCLID, 2013).