Registration Dossier
Registration Dossier
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EC number: 247-978-7 | CAS number: 26761-42-2
Adsorption / desorption
Administrative data
Link to relevant study record(s)
Description of key information
Potassium is an essential macronutrient in aquatic and terrestrial ecosystems. Dissolved potassium occurs in solution as dissociated K+ ions. Although K is an abundant element, its mobility in soils, sediments and suspended matter is limited since it is readily incorporated into clay lattices and it is adsorbed more strongly than Na+ to the surfaces of clay minerals and organic matter (Salminen, 2005). A European median log Kp value of 3.99 L/kg is derived for sediment-water partitioning.
Key value for chemical safety assessment
Other adsorption coefficients
- Type:
- log Kp (solids-water in sediment)
- Value in L/kg:
- 3.99
Other adsorption coefficients
- Type:
- other: desorption coefficient Kd (water-soil) miscible displacement technique, min. Kd
- Value in L/kg:
- 1.2
Other adsorption coefficients
- Type:
- other: desorption coefficient Kd (water-soil) miscible displacement technique, max. Kd
- Value in L/kg:
- 10.9
Additional information
The assessment of the partitioning of potassium in freshwater sediments is based on Kp values derived from monitoring data for elemental potassium concentrations in water and corresponding sediments provided by the FOREGS Geochemical Baseline Mapping Programme that aimed to provide high quality, multi-purpose homogeneous environmental geochemical baseline data for Europe. A total of 745 paired samples, i.e. samples with the same coordinates for the sampling location of stream water (filtered to < 0.45 µm) and sediment (wet sieved in the field to <0.15 mm) were processed (Salminen et al. 2005) and results correspond to steady-state conditions of potassium, independent of potassium speciation. Sampled stream water and sediments cover a wide range of environmental conditions. Water parameters such as pH, hardness and organic carbon concentrations cover several magnitudes.
Since FOREGS sampled on a grid aiming to equally represent geochemical baseline concentrations across Europe, a European median log Kd value of 3.99 is derived for sediment-water partitioning.
In another study on the adsorption capacity of potassium, Kd values from 1.2 to 10.9 L/kg were determined for the desorption of potassium from Ap, A2, B21t, and B22t horizons of two Dothan soils that had been equilibrated with potassium for 96 h and then continuously leached with CaCl2 until equilibrium was reached (miscible displacement). Potassium was faster leached from the upper than from the lower soil horizons and ~95-98% of the initially adsorbed potassium was subsequently desorbed, suggesting that its adsorption-desorption is reversible in these soils (Sparkset al.1980).
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