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EC number: 246-356-2 | CAS number: 24613-89-6
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
Adsorption / desorption
Administrative data
Link to relevant study record(s)
Description of key information
Adsorption for both Chromium (III) and Chromium (VI) is pH dependant. Adsorption of Chromium (III) is stronger in alkaline conditions whereas conversely adsorption of Chromium (VI) is stronger in acidic conditions.
Key value for chemical safety assessment
Additional information
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 available in the EU RAR for a number of soil and sediment types. The following data and discussion are taken from the EU RAR (2005).
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. For the water column, chromium (VI) and chromium (III) have similar adsorption partition coefficients for suspended solids, which are greater than those found for sediment and soil.
Chromium (VI) exists mainly as highly soluble oxoanions in the environment and is expected to be mobile in soils and sediments. The adsorption of chromium (VI) is pH dependent. Under alkaline conditions, chromium (VI) is not readily sorbed and remains highly mobile. In acidic oxidised sediments with a high content of iron and manganese oxides or clay minerals, chromium (VI) should be adsorbed more strongly onto the sediment as the higher net positive charge present in acidic sediment should provide more or stronger sites for adsorption of the chromium (VI) anions. The adsorption is thought to occur with the mineral fraction, especially those with exposed hydroxyl groups on their surface such as iron and aluminium oxides and montmorillonite. Decreasing pH results in increasing protonation of the mineral surface and hence increasing adsorption of the chromium (VI)-containing anions. However, other anions present in natural systems such as SO42-can also compete with the adsorption of chromium (VI), resulting in lower adsorption of chromium (VI) than might be expected. In the environment, iron oxides are the primary site of adsorption for chromium (VI) in acidic to neutral soils, with some contribution also from minerals with aluminium-OH groups.
Summary of measured partition coefficients (Kp) for chromium
Phase |
Kp (l/kg) |
Comments |
Reference |
||
Total Cr |
Cr(VI) |
Cr(III) |
|||
Suspended sediment partition coefficients |
|||||
Kpsusp |
250-50,000 |
25,000-800,000 |
Freshwater and saltwater |
Braunschweiler et al. (1996) |
|
126,000-786,000 |
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) |
|||
324,000 |
Saltwater (0.1-0.5‰), based on routine water quality data from The Netherlands |
Van Der Kooij et al.(1991) |
|||
306,000-320,000 |
Saltwater (1-5‰), based on routine water quality data from The Netherlands |
||||
228,000 |
Saltwater (>10‰), based on routine water quality data from The Netherlands |
||||
140,000-570,000 |
Freshwater (Rhine-Meuse delta) |
Golimowski et al. (1990) |
|||
29,200-200,000 |
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 |
|||||
Kpsed |
940a |
34,000 |
Saltwater, organic matter content ~2%, pH 7.8-8.0 |
Wang et al. (1997) |
|
2,300a |
Saltwater, organic matter content ~10%, pH 7.8-8.0 |
||||
25,600-32,800 |
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 |
||||
11,000 |
Freshwater, pH=4.5 |
Young et al. (1992) |
|||
120,000 |
Freshwater, pH >6 |
||||
Soil-water partition coefficients |
|||||
Kpsoil |
524-24,217 |
Dutch field soils, pH~3.8-7.9; 2-21.8% organic matter |
Janssen et al. (1997) |
||
13-40 |
298-788 |
Loam; pH 6; 1.92% organic carbon |
Hassan and Garrison (1996) |
||
1-6.1 |
2,823-15,382 |
Loam; pH >6; 1.92% organic carbon |
|||
45.4-52.3 |
Loess; pH6; 0.11% organic carbon |
||||
1.5-12.1 |
19,716-55,918 |
Loess; pH>6; 0.11% organic carbon |
|||
17-44.6 |
330-27,151 |
Clay; pH7; 3.75% organic carbon |
|||
1.4-2.0 |
Clay; pH>7; 3.75% organic carbon |
||||
0.35-17.4b |
12-27 |
Sand, pH 4-8 |
Pérez et al. (1988) |
||
21-197 |
Sandy soil, pH 4-8, 0.77% organic matter |
||||
6.6-18.4b |
116-608 |
Sandy loam, pH 4-8, 1.62% organic matter |
Note: a) reduction to chromium
III) occurred in these sediments
b) variation with pH not determined
Overall, chromium (VI) anions can be considered to be mobile in sediments in the environment, except possibly under highly acidic conditions.
Chromium (III) appears to be much 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 value, 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 Kpsuspand Kpsedare 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 Kpsoilfor chromium (VI), allowing more reliable values to be chosen:
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
In general, Chromium (III) is more strongly absorbed than Chromium (VI). Adsorption for both Chromium (III) and Chromium (VI) is pH dependant. Adsorption of Chromium (III) is stronger in alkaline conditions whereas conversely adsorption of Chromium (VI) is stronger in acidic conditions.
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