Registration Dossier
Registration Dossier
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EC number: 207-439-9 | CAS number: 471-34-1
Adsorption / desorption
Administrative data
Link to relevant study record(s)
Description of key information
No studies are available
Key value for chemical safety assessment
Additional information
Soil adsorption/ desorption studies with calcium carbonate are not possible due to analytical difficulties, the solubility characteristics of calcium carbonate in water and calcification.
There is no analytical test method available that could distinguish between contributions to the analysed solution calcium concentration originating from the test material and that originating from the required aqueous solution matrix. Even if the method guideline was amended/deviated from and pure water was used as the aqueous phase for the soil/solution systems, a significant contribution of dissolved calcium would be expected in all samples due to the presence of calcium carbonate and other calcium salts as a naturally occurring mineral fraction in soils. Therefore, it would not be possible to distinguish between contributions to the analysed solution calcium concentration originating from the test material and that originating from the soils themselves.
Calcium carbonate presents only limited solubility in water and solubility characteristics are known to be sensitive to both solution pH and also the presence/partial pressure of carbon dioxide (which dissolves to give carbonate or bicarbonate ions). Therefore, changes with respect to aqueous phase pH and dissolved carbon dioxide concentrations on exposure to soils may lead to shifts in the relative solubility of the test material and potential precipitation and sedimentation on centrifugation of the samples; a process which can not be separated analytically from any true adsorption onto the soil phases.
The accumulation and mobility of calcium carbonate in soils has been documented in soil chemistry as the process of “calcification”. Calcification is the general process by which naturally occurring calcium carbonate or the product of dissolved calcium ions and either bicarbonate or carbonate ions (from dissolved carbon dioxide, the dominant form of the dissolved product being dependant on the solution pH) accumulates in soils. Most commonly, calcium carbonate accumulates in subsurface horizons of soils in subhumid, semiarid, or arid regions. Calcium carbonate has a propensity to leach through soil if water is applied, i.e. it does have some mobility through soil, providing sufficient water is present. As it moves downwards into layers where the water content is low, the leaching will stop. On this basis, calcium carbonate does not have a high potential for adsorption to soil.
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