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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Partition coefficients for different environmental compartments (sediment, suspended particulate matter, soil) have been proposed in the RIVM-report (Crommentuyn et al, 1997).
- The value for the soil that is given for barium in this report is put forward for exposure and risk assessment purposes.
- For the sediment compartment the typical Kd based on FOREGS data is put forward as a reliable value for Europe.
- A value of 1.5 has been proposed as a relevant ratio between the Kd for sediment and the Kd for suspended matter S(tortelder et al, 1989; Van de Meent et al, 1990), and this ratio was also used by RIVM for setting relevant Kd-values for various metals. Application of this factor on the KD,sediment of 3,478 L/kg, results in an estimated Kd,part.matter of 5,217 L/kg, or a log Kd,part.matter of 3.72. This value is supported by Kd values for suspended matter that were reported by Popp and Laquer (1980) for N-American Rivers (range of Log Kd:2.65-3.91) and the value derived by Li et al (1984) for the River Hudson (log Kd: 3.78).

Key value for chemical safety assessment

Additional information

Values for Ba-Kd for sediment, suspended matter and soil were reported by the Dutch National Institute for Public Health and the Environment (RIVM, The Netherlands) in their report “Maximum permissible concentrations and negligible concentrations for metals, taking background concentrations into account” by Crommentuyn et al (1997). Results were discussed within the “Peer Review Committee” of the centre for Substances and Risk Assessment prior to publication. In this report, partition coefficients for the distribution of metals between particulate matter and water were used to calculate the dissolved background concentrations from the total background concentration in surface water (application of the equilibrium partitioning method). RIVM conducted a literature search, and also found little data on partition coefficients for Ba to soil and sediment.

For sediment and particulate matter, Crommentuyn et al (1997) reported that Bockting et al. (1992) derived log Kds for different metals, including barium, thereby using the methodology that was described in Stortelder et al (1989). The typical log-values that were derived by RIVM for Ba were based on measurements in North American rivers (data in Popp and Laquer (1980) and Li et al, 1984; log Kd values ranging between 2.65 and 3.91), and were 3.13 and 3.00 for particulate matter and sediment, respectively. These values correspond to a Kd,part.matter value and Kd,sediment value of 1,349 L/kg and 1,000 L/kg, respectively.

Bockting et al (1992) also reported Kd,soil values for different metals. For Ba, the proposed logKd,soil was 1.78, which corresponds to a Kd,soil value of 60.3 L/kg. This value is a relevant data point for calcium, but as the complexion properties of Ba-ions are comparable to those for Ca (Smith and Martell, 1976), this value is considered a reliable estimate for the Kd of Ba to soil. It should be noted, though, that the electrostatic adsorption of Ba by soils is somewhat stronger than for Ca.

Data from FOREGS:

The FOREGS Geochemical Baseline Mapping Programs main aim was to provide high quality, multi-purpose environmental geochemical baseline data for Europe. The sampling sites selected for stream water analyses of dissolved metals were typical of locally unimpacted or slightly impacted areas. Consequently, the metal concentrations that are determined in these samples can be considered as relevant baseline concentrations. A total number of 807 water samples were analyzed for Ba by ICP-MS (detection limit 0.0005 µg/L); dissolved barium levels ranged between 4 and 436 µg/L. For the sediment compartment, the amount of analyzed samples was 845, with barium levels ranging between 31 mg/kg and 3,122 mg/kg. Sediment samples were analyzed by ICP-AES, after aqua regia destruction of the sediment samples (aggressive removal of the the compete exchangeable fraction). Raw data were sub-categorized per country, and a typical baseline value (i.e., 50th percentile or median) of barium in water and sediment were determined for each country. Assuming that the country-specific median values are relevant for both compartments and represent a state of chemical equilibrium, a typical Kd-value can be derived for each country. Typical country-specific log Kd values are situated between 2.84 and 4.76, with an overall typical value of 3.54 for Europe. This value is relatively close to the value of 3.00 that was reported in the RIVM report, but which was based on a limited amount of data points

A summary of the selected partition coefficients of barium for different environmental compartments is given below

 Compartment Kd-value (L/kg)  Log Kd  Reference
Sediment  3,478  3.54  Salminen et la (2005; FOREGS data) 
Suspended particulate matter  5,217  3.72  Estimated data (ratio of 1.5 on, Kd,sediment) 
Soil  60.3  1.78  Crommentuyn et al (1997) 

These data suggest that the KD,soil

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