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Endpoint:
adsorption / desorption
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Data were accepted and proposed by the Dutch "National Institute of Public Health and the Environment" (RIVM, Rijksinstituut voor Volksgezondheid en Milieu) in their study report "Maximum permissible concentrations and negligible concentrations for metals, taking background concentrations into account". Reported adsorption coefficients were derived from other studies/reports that were evaluated by RIVM.
Qualifier:
no guideline available
Principles of method if other than guideline:
Reported value is based on literature study:
1) Bockting GMJ, Van de Plassche EJ, Strujs J, Canton JH, 1992. Soil-water partition coefficients for some trace metals. RIVM report No. 679101 003 - using batch experiments
2) Popp CJ, Laquer F, 1980. Trace metal transport and partitioning in the suspended sediments of the Rio Grande and tributaries in Central New Mexico. Chemosphere 9, 89-98.
3) Li Y, Burkhardt L, Teraoka H, 1984. Desorption and coagulation of trace elements during estuarine mixing. Geochimica et Cosmochimica Acta 48, 1879-1884.
GLP compliance:
not specified
Type of method:
batch equilibrium method
Media:
suspended matter
Radiolabelling:
not specified
Test temperature:
not further details
Analytical monitoring:
not specified
Details on sampling:
not further details
Details on matrix:
no further details
Details on test conditions:
no further details
Computational methods:
no further details
Phase system:
suspended matter-water
Type:
log Kp
Value:
3.13 dimensionless
Details on results (Batch equilibrium method):
log Kp(suspended matter/water): 3.13
Kp(suspended matter/water): 1349 L/kg
Statistics:
not further details
Validity criteria fulfilled:
not specified
Conclusions:
The experimentally determined partition coefficient for barium between suspended matter and water (log Kp(spm/w) that is put forward by RIVM is 3.13, which corresponds to a Kp(spm/w) of 1349 L/kg. This value is considered as a relevant and reliable data point for this specific parameter.
Endpoint:
adsorption / desorption
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Original publication was not evaluated, but data were evaluated and used by the Dutch authorities (RIVM) for the derivation of a Kp for suspended matter. Data and information on methodology were also given and discussed in Bockting et al. (1992).
Qualifier:
no guideline followed
Principles of method if other than guideline:
Barium levels were measured in water (dissolved fraction) and in suspended particulate matter, using a radiotracer.
GLP compliance:
not specified
Type of method:
other: field data
Media:
suspended matter
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Subsamples of unfiltered Hudson river water samples spiked with a radiotracer were taken at predetermined intervals
Details on test conditions:
Batch experiments with particulate matter from the Hudson River (USA). Radiotracer was added to unfiltered water. The spikes did not greatly change the natural concentration of Ba, as the radiotracer was carrier free and the amounts of spikes were small. Samples were shaken for 20 days at 2°C.
Phase system:
suspended matter-water
Type:
log Kp
Value:
3.78 dimensionless
Remarks on result:
other: Hudson River
Phase system:
suspended matter-water
Type:
log Kp
Value:
2.66 dimensionless
Remarks on result:
other: Hudson River + sea water
Adsorption and desorption constants:
Hudson river water: log Kp=3.78 (6,025 L/kg)
A 4 to 1 mixture with filtered seawater: log Kp=2.66 (457 L/kg)
Details on results (Batch equilibrium method):
Kp values for unfiltered Hudson river water and a 4 to 1 mixture with filtered seawater were determined (equilibration period of 20 days)
Conclusions:
Using a radiotracer, barium levels were determined in water and in suspended matter, resulting in Kp values ranging between 457 (river water mixed with seawater) and 6,026 L/kg (Hudson River water). Data were used by Dutch authorities (RIVM) for the determination of a Kp value for barium for suspended matter. Data are therefore considered reliable and useful for the determination of a typical Kp suspended matter-water in a weight-of-evidence approach.
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Original publication was not evaluated, but data were evaluated and used by the Dutch authorities (RIVM) for the derivation of a Kp for suspended matter. Data were also given and discussed in Bockting et al. (1992).
Qualifier:
no guideline followed
Principles of method if other than guideline:
Barium levels were measured in water (dissolved fraction) and in suspended particulate matter.
GLP compliance:
not specified
Type of method:
other: field data
Media:
suspended matter
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Particulate matter was collected by centrifugation or filtering of large water volumes through 0.45 micrometer filters
Phase system:
suspended matter-water
Type:
log Kp
Value:
3.91 dimensionless
Remarks on result:
other: Rio Grande
Phase system:
suspended matter-water
Type:
log Kp
Value:
2.89 dimensionless
Remarks on result:
other: Rio Puerco
Phase system:
suspended matter-water
Type:
log Kp
Value:
2.65 dimensionless
Remarks on result:
other: Rio Salado
Adsorption and desorption constants:
Rio Grande: 8,128 L/kg (log: 3.91)
Rio Puerco: 776 L/kg (log: 2.89)
Rio Salado: 447 L/kg (log: 2.65)
Details on results (Batch equilibrium method):
The Kp values for North American rivers (data from Popp and Laquer, 1980) are calculated from average aqueous concentrations (8-12 samples, geometric mean) and metal contents of particulate matter (around 8 samples).
Statistics:
Kp= suspended matter barium concentration / water barium concentration
Conclusions:
Barium levels were determined in water and in suspended matter, resulting in Kp values ranging between 447 and 8,128 L/kg. Information on sampling methodology and number of samples for each river is provided in Bockting et al. (1992) and Crommentuijn et al. (1997). Data were used by Dutch authorities (RIVM) for the determination of a Kp suspended matter-water for barium. Data are therefore considered reliable and useful for the determination of a typical Kp in a weight-of-evidence approach.
Endpoint:
adsorption / desorption, other
Remarks:
other: monitoring data in water and sediment
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Kp values are based on reliable field data of concentration levels in water and sediment; no standard guideline test was followed for generating Kp values. Kp values are calculated based on the hypothesis that equilibrium exists between the baseline levels in water and in sediment.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Baseline levels of barium in water and sediment were determined in >800 pristine locations. Assuming equilibrium between both environmental compartments, site-specific sediment-water partitioning coefficients were derived
GLP compliance:
not specified
Type of method:
other: field data of baseline levels in water and sediment
Media:
sediment
Radiolabelling:
no
Test temperature:
environmentally relevant temperatures
Analytical monitoring:
yes
Details on sampling:
Water compartment:
- running stream water was collected from small, second order drainage basins (<100 km²);
- whenever possible, sampling was performed during winter and early spring months, and was avoided during rainy periods and flood events;
- a full description of sampling materials and sampling volumes is provided, and all materials were rinsed twice with unfiltered or filtered stream water (depending on the type of water sample);
- all potential contaminating factors were reduced during the sampling period (wearing of gloves, no smoking in the area allowed, no hand jewelry was allowed, running vehicles during sampling was prohibited, etc.)

Sediment compartment:
- sediment samples were taken at the same locations that were selected for the determination of background concentrations in the surface water;
- sampling was also performed in such a way that any kind of metal contamination was avoided (e.g., no hand jewelry, no medical dressing, etc);
- if it was not possible to use non-metal equipment (e.g., spades, sieves), unpainted steel equipment was used (no aluminium or brass);
- a composite sample was made from subsamples taken from beds of similar nature (ISO-5667-12, 1995), and minimum amount of sediment sample was 0.5 kg dry wt.
Phase system:
sediment-water
Type:
log Kp
Value:
2.84 dimensionless
Remarks on result:
other: lowest country-specifc typical value (Estland)
Phase system:
sediment-water
Type:
log Kp
Value:
4.76 dimensionless
Remarks on result:
other: highest country-specific typical value (Slovenia)
Phase system:
sediment-water
Type:
log Kp
Value:
3.54 dimensionless
Remarks on result:
other: typical EU-value
Adsorption and desorption constants:
Country-specific log Kp-values are situated between 25 (Estonia) and 4.76 (Slovenia), with a median value of 3.54 (3478 L/kg) which is derived from the best fitted distribution that was developed with all country-specific Kp-values
Details on results (Batch equilibrium method):
A typical (i.e., median) Kp-value was determined for each EU-country, and the median value of all these country-specifc Kp's is considered as a reliable typical Kp-sediment for Europe.
Statistics:
Kp = sediment barium concentration / water column barium concentration
A distribution was fitted through all country-specific Kp-values: From this distribution a median log Kp of 3.54 (3,478 L/kg) for barium in European sediments is derived.
Conclusions:
Reliable baseline levels of barium in pristine water/sediment samples were determined in >800 samples. Sampling and analytical procedures are considered adequate and resulted in reliable data. Assuming equilibrium between the typical concentration in water and sediment, relevant Kp values were generated for each country. Data are therefore considered useful for the determination of a relevant Kp for the sediment compartment.
Endpoint:
adsorption / desorption
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Data were accepted and proposed by the Dutch "National Institute of Public Health and the Environment" (RIVM, Rijksinstituut voor Volksgezondheid en Milieu) in their study report "Maximum permissible concentrations and negligible concentrations for metals, taking background concentrations into account". Reported adsorption coefficients were derived from other studies/reports that were evaluated by RIVM.
Qualifier:
no guideline available
Principles of method if other than guideline:
Adsorption of barium is assumed to be comparable with that of calcium. Data for calcium are taken from Scheffer et al. (1984).
GLP compliance:
not specified
Type of method:
other: not specified
Media:
soil
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
no further details
Radiolabelling:
not specified
Test temperature:
no further details
Analytical monitoring:
not specified
Details on sampling:
no further details
Details on matrix:
no further details
Details on test conditions:
no further details
Computational methods:
no further details
Phase system:
soil-water
Type:
log Kp
Value:
1.78 dimensionless
Details on results (Batch equilibrium method):
log Kp(soil/water): 1.78
Kp(soil/water): 60.3 L/kg
Statistics:
no further details
Validity criteria fulfilled:
not specified
Conclusions:
The partition coefficient for barium between soil and water (log Kp(soil/w)) that is put forward by RIVM is 1.78, which corresponds to a Kp(soil/w) of 60.3 L/kg. This value is a relevant data point for calcium, but as the complexation properties of barium ions are comparable to those for calcium (Smith and Martell, 1976), this value is considered a reliable estimate for the adsorption capacity of Ba to soil particles. It should be kept in mind though that the electrostatic adsorption of barium by soil particles is somewhat stronger than for calcium.
Endpoint:
adsorption / desorption: screening
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
For this endpoint, data on the adsorption of barium (and calcium for the adsorption to soil) to particulate matter is used.
For further explanation on the read across approach, reference can be made to the read across justification document attached to IUCLID Section 13.
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Phase system:
suspended matter-water
Type:
log Kp
Value:
3.13 dimensionless
Remarks on result:
other: Barium - Crommentuijn 1997
Phase system:
suspended matter-water
Type:
log Kp
Value:
3.78 dimensionless
Remarks on result:
other: Barium - Li 1984
Remarks:
Hudson River
Phase system:
suspended matter-water
Type:
log Kp
Value:
2.66 dimensionless
Remarks on result:
other: Barium - Li 1984
Remarks:
Hudson River + sea water
Phase system:
suspended matter-water
Type:
log Kp
Value:
3.91 dimensionless
Remarks on result:
other: Barium - Popp and laquer 1980
Remarks:
Rio Grande
Phase system:
suspended matter-water
Type:
log Kp
Value:
2.89 dimensionless
Remarks on result:
other: Barium - Popp and laquer 1980
Remarks:
Rio Puerco
Phase system:
suspended matter-water
Type:
log Kp
Value:
2.65 dimensionless
Remarks on result:
other: Barium - Popp and laquer 1980
Remarks:
Rio Salado
Phase system:
sediment-water
Type:
log Kp
Value:
2.84 dimensionless
Remarks on result:
other: Barium - Salminen 2005
Remarks:
lowest country-specifc typical value (Estland)
Phase system:
sediment-water
Type:
log Kp
Value:
4.76 dimensionless
Remarks on result:
other: Barium - Salminen 2005
Remarks:
highest country-specific typical value (Slovenia)
Phase system:
sediment-water
Type:
log Kp
Value:
3.54 dimensionless
Remarks on result:
other: Barium - Salminen 2005
Remarks:
typical EU-value
Phase system:
soil-water
Type:
log Kp
Value:
1.78 dimensionless
Remarks on result:
other: Calcium - Crommentuijn 1997

Description of key information

Five studies were used in a weight of evidence approach to cover the endpoint. Data were available for soil, suspended matter, and sediment. The following final key values were retained: a log Kp of 3.72 for suspended matter-water, a log Kp of 3.54 for sediment-water, and a log Kp of 1.78 for soil-water. Adsorption to sediment and suspended matter appears to be more pronounced for barium than adsorption to soil particles.

Key value for chemical safety assessment

Other adsorption coefficients

Type:
log Kp (suspended matter-water)
Value in L/kg:
3.72

Other adsorption coefficients

Type:
log Kp (sediment-water)
Value in L/kg:
3.54

Other adsorption coefficients

Type:
log Kp (soil-water)
Value in L/kg:
1.78

Additional information

In total, five studies were selected as useful for covering the adsorption/desorption endpoint using a weight of evidence approach. Data were available for soil, sediment, and suspended matter and will be further discussed below.

For soil, one study was included in the weight of evidence approach. Crommentuijn et al. (1997) reported a partition coefficient for barium between soil and water (log Kp(soil/w)) of 1.78, which corresponds to a Kp(soil/w) of 60.3 L/kg. This value is a relevant data point for calcium taken from Scheffer et al. (1984), but as the complexation properties of barium ions are comparable to those for calcium (Smith and Martell, 1976), this value is considered a reliable estimate for the adsorption capacity of barium to soil particles. It should be noted, though, that the electrostatic adsorption of barium by soils is somewhat stronger than for calcium.

For sediment one study was included in the weight of evidence approach, i.e. Salminen et al. (2005). In this study, baseline levels of barium in pristine water/sediment samples were determined in >800 samples from various countries in Europe. Sampling and analytical procedures are considered adequate and resulted in reliable data. Assuming equilibrium between the typical concentration in water and sediment, relevant Kp values were generated for each country. These data are considered useful for the determination of a relevant Kp for the sediment compartment. A distribution was fitted through all country-specific Kp values. From this distribution a median log Kp of 3.54 (3,478 L/kg) for barium in European sediments is derived. This value corresponds very well to the log Kp value of 3.0 (1,000 L/kg) reported by Crommentuijn et al. (1997). That value was not an experimentally determined value, instead, as proposed by Stortelder et al. (1989), Bockting et al. (1992), and Van de Meent et al. (1990), the Kp sediment-water was calculated from the experimentally derived values for Kp suspended matter-water, dividing the latter by a factor of 1.5 to compensate for the typically observed lower adsorption to sediments compared to suspended matter. Then, the median Kp sediment-water was calculated from these values.

For suspended matter, three studies were identified as useful. Crommentuyn et al. (1997), in their study for the Dutch government on maximal permissible concentrations for metals, derived a partition coefficient for barium between suspended matter and water (log Kp(spm/w)) of 3.13, which corresponds to a Kp(spm/w) of 1349 L/kg, based on data from Popp and Laquer (1980) and Li et al. (1984). The study of Popp and Laquer (1980) determined barium levels in water and in suspended matter in several rivers, resulting in Kp values ranging between 447 and 8,128 L/kg. Further, Li et al. (1984) determined barium levels in water and in suspended matter in Hudson River water as well as in a mixture of Hudson River water and seawater, resulting in Kp values ranging between 457 (river water mixed with seawater) and 6,026 L/kg (Hudson River water). These values are considered as relevant and reliable data points for this specific parameter. However, because these values were all determined in North-American waters, it was considered more appropriate for European waters to derive a log Kp suspended matter-water by adjusting the Kp sediment-water value calculated from the data reported by Salminen et al. (2005) to account for the (typically observed) factor 1.5 difference between Kp suspended matter-water and Kp sediment-water, as suggested by the authors mentioned in the previous paragraph. This results in a Kp of 5,217 L/kg (log Kp of 3.72), which is considered as key value for characterising the distribution of barium between suspended matter and water, representative for European waters.

Overall, the obtained adsorption coefficients were similar as for many other metals. Adsorption to soil appears to be mild, however a stronger adsorption of barium to suspended matter and sediment seems to occur.