Disodium tetrachloropalladate

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption, other

Remarks:

measured adsorption/desorption values

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: No guideline followed and is not GLP compliant, however, study meets generally accepted scientific methods and is described in sufficient detail

Principles of method if other than guideline:

Laboratory study, no guideline followed

GLP compliance:

not specified

Type of method:

batch equilibrium method

Media:

sediment

Radiolabelling:

no

Test temperature:

23 +/- 1 degrees Celsius

Analytical monitoring:

not specified

Details on sampling:

Field collected whole water samples were spiked with Pd to a concentration of 10 µg l-1 and shaken for 48 hours, followed by fractionation using 0.45 µm filtration.

Details on matrix:

Location: lower catchment of the Tugela river and its estuary, South Africa
Collection date: March 2006 (rainy season)

Details on test conditions:

Concentration of suspended particulate matter: between 150 and 200 mg l-1 (although one of the samples contained approximately 600 mg l-1 of suspended matter due to resuspension of bed sediment)
Concentration of suspended particulate matter in saline sample (estuarine mixing experiments): approximately 15 mg l-1 suspended matter
Salinity of seawater: 33.6 %
pH (freshwater): between 6.8 and 7.9
pH (seawater): 8.4
Dissolved organic carbon concentration: between 1.0 and 2.7 mg l-1 (although one sample contained a DOC concentration of 106 mg l-1)

Type:

other: log Kd

Value:

3.59

Temp.:

23 °C

Remarks on result:

other: Mean for all salinities, standard deviation 0.41

Type:

other: log Kd

Value:

3.39

Temp.:

23 °C

Remarks on result:

other: Mean for freshwaters, standard deviation 0.40

Type:

other: log Kd

Value:

3.84

Temp.:

23 °C

Remarks on result:

other: Mean for estuarine waters, standard deviation 0.04

Type:

other: log Kd

Value:

4.21

Temp.:

23 °C

Remarks on result:

other: Single value for seawater, salinity 33 %

Kd values are slightly affected by salinity with slightly higher partitioning at salinities above 10 ‰, partitioning in freshwaters showed a limited range of variation. The overall variation in log Kd for palladiumwas between 2.7 and 4.2 in river waters, estuarine (mixtures), and seawater. A mean log Kd of 3.59 (stdev 0.41) was observed for all salinities, a mean log Kd of 3.39 (stdev 0.40) was observed for freshwaters only, a mean log Kd of 3.84 (stdev 0.04) was observed for estuarine waters only, and a single log Kd of 4.21 was determined in seawater (salinity 33 ‰).

Table 1. Adsorption results

Salinity (%)	Kd (L/kg)	Log Kd
3.00	3000	3.48
3.50	3500	3.48
5.00	5000	3.70
5.00	5000	3.70
5.00	5000	3.70
5.50	5500	3.74
6.00	6000	3.78
7.00	7000	3.85
7.00	7000	3.85
8.00	8000	3.90
16.28	16280	4.21

Validity criteria fulfilled:

not specified

Conclusions:

Kd values are slightly affected by salinity with slightly higher partitioning at salinities above 10 ‰, partitioning in freshwaters showed a limited range of variation. The overall variation in log Kd for palladiumwas between 2.7 and 4.2 in river waters, estuarine (mixtures), and seawater. A mean log Kd of 3.59 (stdev 0.41) was observed for all salinities, a mean log Kd of 3.39 (stdev 0.40) was observed for freshwaters only, a mean log Kd of 3.84 (stdev 0.04) was observed for estuarine waters only, and a single log Kd of 4.21 was determined in seawater (salinity 33 ‰).

Executive summary:

This study has a reliability rating of 2, as it does not follow a standard guideline and is not GLP compliant, but meets generally accepted scientific methods and is described in sufficient detail. This study investigated the partitioning of several precious metals in river water and mixtures of river water and seawater mimicking an estuarine salinity gradient. Separations were performed by filtration at 0.45 µm, with subsequent Pd analysis by ICP-MS. Kd values are slightly affected by salinity with slightly higher partitioning at salinities above 10 ‰, partitioning in freshwaters showed a limited range of variation. A mean log Kd of 3.39 (stdev 0.40) was observed for freshwaters, a mean log Kd of 3.84 (stdev 0.04) was observed for estuarine waters only, and a single log Kd of 4.21 was determined in seawater (salinity 33 ‰).

Description of key information

The log Kd for suspended particulate matter (SPM) in freshwater is 3.39 (stdev 0.40) and the average Kd is 2455 L/kg. Where wastewater is discharged to marine water it is recommended to use the measured partition coefficient in seawater, log Kd 4.21 (i.e. Kd is 16220 L/kg). The log Kd for soil is 2.64 (stdev 0.48) and the average Kd is 436.5 L/kg. For the exposure assessment the log Kd value from the suspended solids was used in case no value was available.

Key value for chemical safety assessment

Other adsorption coefficients

Type:

log Kp (solids-water in soil)

Value in L/kg:

2.64

at the temperature of:

25 °C

Other adsorption coefficients

Type:

log Kp (solids-water in suspended matter)

Value in L/kg:

3.39

at the temperature of:

23 °C

Other adsorption coefficients

Type:

log Kp (solids-water in sediment)

Value in L/kg:

3.39

at the temperature of:

23 °C

Additional information

Two high quality studies have determined the partitioning of Pd between river water and suspended particulate matter. Both studies showed relatively consistent results for experiments performed in freshwaters, and similar partitioning was also observed in both estuarine and marine water in the key study (Turner et al., 2006; Cobelo-Garcia et al., 2008). A high quality study of the partitioning of palladium to two soils and one sediment provides information relevant to the soil compartment (Sako et al., 2009).

 

Average partition coefficients have been derived in cases where multiple partition coefficients are available for the same type of system (e. g. partitioning to suspended particulate matter in surface waters). The average values have been derived by calculating the log values of the individual partition coefficients (Kd). Following log transformation, the mean and standard deviation are calculated to define an "average" partition coefficient and its associated standard deviation, assuming a log-normal distribution of Kd values. The log Kd across all waters studied is 3.59 and the average Kd across all salinities is 3890.5 L/kg (st dev 0.41). Averaging of Kd values obtained from tests at different salinities hides a clear difference in the partitioning behaviour of palladium between fresh and marine waters, with stronger partitioning being observed in marine water. Consequently, separate Kd values are recommended for assessments of freshwater and marine systems. The log Kd for freshwater is 3.39 (stdev 0.40) and the average Kd is 2455 L/kg. The log Kd for marine water is 4.21, and the Kd is 16220 L/kg. The log Kd for soil is 2.64 (stdev 0.48) and the average Kd is 436.5 L/kg.