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EC number: 215-219-9
CAS number: 1314-11-0
Strontium oxide dissolves upon contact
and during the reaction with water. The water solubility test of
strontium oxide (OECD TG 105) indicates a high dissolution from
strontium oxide (≤7.63 g/L at 20°C) and a corresponding increasing
solution pH to a pH > 13. Due to the buffering capacity of most
environmental systems, it may reasonable be assumed that the formed
hydroxide ions are neutralised in the environment by different processes
The solubility of strontium is not
greatly affected by the presence of most inorganic anions as there is
little tendency for strontium to form complexes with inorganic ligands
(Krupka et al. 1999. EPA 402-R-99-004B and references therein). Free
Sr2+ cations are mobile under most environmental conditions, despite the
relatively low solubility of strontium carbonate andstrontium sulfateat
neutral to high pH. In solutions with a pH below 4.5, Sr2+ ions are
predominant. Strontium sulfate forms at more neutral conditions (pH 5 to
7.5). Only under highly alkaline conditions, strontium carbonate
controls dissolved strontium concentrations. Further, dissolved
strontium forms only weak aqueous complexes with chloride and nitrate
(Salminen et al. 2015 and references therein, Krupka et al. 1999. EPA
Regarding monodentate and bidentate
binding to negatively-charged oxygen donor atoms, including natural
organic matter, alkaline earth metals, such as strontium, tend to form
complexes with ionic character as a result of their low
electronegativity. Ionic bonding is usually described as resulting from
electrostatic attractive forces between opposite charges, which increase
with decreasing separation distance between ions (Carbonaro and Di Toro.
2007. Geochim Cosmochim Acta 71 3958–3968; Carbonaro et al. 2011.
Geochim Cosmochim Acta 75: 2499-2511 and references therein). Thus,
strontium does not form strong complexes with fulvic or humic acids
based on the assumption that strontium would exhibit a similar (low)
stability with organic ligands as calcium and that strontium could not
effectively compete with calcium for exchange sites because calcium
would be present at much greater concentrations (Krupka et al. 1999. EPA
In sum, strontium ions are highly
mobile, occur only in one valence state (2+), i.e. are not oxidized or
reduced, and do not form strong complexes with most inorganic and
organic ligands (Krupka et al. 1999. EPA 402-R-99-004B; Salminen et al.
2015). Thus, it may further be assumed that the behaviour of the
dissociated strontium ions in the environment determine the fate of
strontium upon dissolution with regard to (bio)degradation,
bioaccumulation, partitioning as well as the distribution in
environmental compartments (water, air, sediment and soil) and
subsequently the ecotoxicological potential.
Therefore, the assessment of the
environmental fate and subsequently ecotoxicity of strontium oxide is
based on elemental strontium concentrations. Read-across of data
available for soluble strontium substances is applied since the
strontium ions determine the environmental fate of strontium.
Abiotic degradation: Abiotic
degradation including hydrolysis or phototransformation in water, soil
or air, are not relevant for the environmental fate of inorganic
substances including strontium and strontium oxide.
Biotic degradation: Biodegradation is not
relevant for metals and metal compounds, including strontium
and strontium oxide.
has a low potential to bioconcentrate or bioaccumulate in aquatic and
/ desorption: Geochemical
background data providing a total of 757 paired samples resulted in a
Europe-wide median stream water/sediment Kd for strontium of 915 L/kg.
Additional published data reported Kd values for the soil compartment
ranging from 27.5 to 310 L/kg strontium (median). A weight of evidence
approach resulted in an overall median soil Kd value of 65 L/kg
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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