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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Adsorption of Chromium (III) is stronger in alkaline conditions.  There are no proprietary studies investigating the adsorption/desorption of the substance. The estimation methods given in the main Technical Guidance document for determining adsorption coefficients for soil, sediment and suspended sediment are not applicable to chromium compounds. Measured values are avaiolable in the EU RAR for a number of soil and sediment types. 
In general, Chromium (III) is more strongly absorbed than Chromium (VI). Adsorption is pH dependant. Adsorption of Chromium (III) is stronger in alkaline conditions.

Key value for chemical safety assessment

Additional information

Discussion of adsorption coefficients for chromium

The table below summarises the published values for Kpwater-solids for both freshwater and marine environments. The values are reported according to a variety of methods and may not be directly comparable; however, they do give a general indication of the partitioning of chromium (VI) in the environment relative to that of total chromium and/or chromium (III) for several environmental compartments. In general, chromium (III) is more likely to partition to solids in the sediment and soil.

Summary of measured partition coefficients (Kp) for chromium


Kp (l/kg)



Total Cr



Suspended sediment partition coefficients




Freshwater and saltwater
 Netherlands estimate

Braunschweiler et al. (1996)

median 290,000

Freshwater, based on routine water quality data from The Netherlands

Van Der Kooij et al. (1991)

30,100-1,059,600; mean 322,400

Freshwater River suspended sediments, United States - based on monitoring data

Young et al. (1987)


Saltwater (0.1-0.5‰), based on routine water quality data from The Netherlands

Van Der Kooij et al. (1991)


Saltwater (1-5‰), based on routine water quality data from The Netherlands


Saltwater (>10‰), based on routine water quality data from The Netherlands


Freshwater (Rhine-Meuse delta)

Golimowski et al. (1990)


Saltwater (Tyrrhenian Sea), silty-clay sediment, organic carbon content 1.6%, salinity 3.8‰, pH 8.2-8.3.

Ciceri et al. (1992)

Sediment-water partition coefficients




Saltwater, organic matter content ~2%, pH 7.8-8.0

Wang et al. (1997)


Saltwater, organic matter content ~10%, pH 7.8-8.0


Freshwater, pH 8.3, organic carbon content 2.65%

Young et al. (1987)

60-44,800; mean 7,100

Freshwater River sediments, United States -based on monitoring data


Freshwater, pH=4.5

Young et al. (1992)


Freshwater, pH >6

Soil-water partition coefficients



Dutch field soils, pH~3.8-7.9; 2-21.8% organic matter

Janssen et al. (1997)



Loam; pH 6; 1.92% organic carbon

Hassan and Garrison (1996)



Loam; pH >6; 1.92% organic carbon


Loess; pH6; 0.11% organic carbon



Loess; pH>6; 0.11% organic carbon



Clay; pH7; 3.75% organic carbon


Clay; pH>7; 3.75% organic carbon



Sand, pH 4-8

Pérez et al. (1988)


Sandy soil, pH 4-8, 0.77% organic matter



Sandy loam, pH 4-8, 1.62% organic matter

Chromium (III) appears to be more strongly adsorbed to soils and sediments than chromium (VI). The adsorption of chromium (III) onto soil follows the pattern typical of cationic metals and increases with increasing pH (lowering pH results in increased protonation of the adsorbent leading to fewer adsorption sites for the cationic metal) and the organic matter content of the soil and decreases when other competing (metal) cations are present. Certain dissolved organic ligands may also reduce the adsorption of chromium (III) to the solid phase by forming complexes which enhance the solubility of chromium (III) in the aqueous phase. Based on the available measured values for the adsorption coefficients the values indicated below will be used in the risk assessment. These values are not taken directly from specific tests, but have been chosen by the Rapporteur to be representative for acidic-neutral and neutral-alkaline environments. The values do not correspond to any specific individual test results, nor are they derived statistically from the available data (since these are insufficient to allow meaningful values to be derived). Instead they were selected by inspection of the data to reflect the available information under the two sets of conditions and to reflect the differences between these. Acid-neutral environments are considered to be those at pH 5 and below; neutral-alkaline environments are taken to be those at pH 6 and above. For chromium (VI), the choice of a reliable adsorption coefficient, particularly for suspended sediment and sediment, is difficult as reduction to chromium (III) (resulting in enhanced adsorption) cannot be ruled out in most of the available data. The values chosen for Kpsusp and Kpsed are therefore the best estimate that can be made assuming that the adsorption of chromium (VI) is substantially less than that seen for chromium (III) and that the adsorption is higher under acidic conditions than alkaline conditions. There are much better data available for the values of Kpsoil for chromium (VI), allowing more reliable values to be chosen (EU RAR, 2005).


Chromium (VI)                     Acid conditions                      Alkaline conditions


Kpsusp = 2,000 l/kg              Kpsusp = 200 l/kg

Kpsed = 1,000 l/kg                Kpsed = 100 l/kg

Kpsoil = 50 l/kg                     Kpsoil = 2 l/kg

Chromium (III)

Acid conditions

Alkaline conditions


Kpsusp = 30,000 l/kg

Kpsusp = 300,000 l/kg


Kpsed = 11,000 l/kg

Kpsed = 120,000 l/kg


Kpsoil = 800 l/kg

Kpsoil = 15,000 l/kg


The equivalent values for the dimensionless form of the partition coefficient using the methods given in the Technical Guidance document are:

Chromium (VI)         Acid conditions                                              Alkaline conditions

Ksusp-water = 500 m3 /m3                               Ksusp-water = 50 m3 /m3

Ksed-water = 500 m3 /m3                                 Ksed-water = 50 m3 /m3

Ksoil-water = 75 m3 /m3                                  Ksoil-water = 3.2 m3 /m3

Chromium (III)          Acid conditions                                  Alkaline conditions

Ksusp-water = 7,500 m3/m3                    Ksusp-water = 75,000 m3/m3

Ksed-water = 5,500 m3/m3                     Ksed-water = 60,000 m3/m3

Ksoil-water = 1,200 m3/m3               Ksoil-water = 22,500 m3/m3


The following information is taken into account for any environmental exposure assessment:


As conclusion from the EU RAR (2005), adsorption of chromium (III) is stronger in alkaline conditions and typically stronger than for chromium (VI).