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Endpoint:
adsorption / desorption, other
Remarks:
field study
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
Reference:
Composition 0
Qualifier:
no guideline followed
Principles of method if other than guideline:
Log Kp values calculated from analysed concentrations of Gd in field samples.
GLP compliance:
not specified
Type of method:
other: field study
Media:
suspended matter
Test material information:
Composition 1
Radiolabelling:
no
Test temperature:
Ambient temperature, not specified
Analytical monitoring:
yes
Details on sampling:
Water samples were collected from a fishing boat using a hand-made polyethylene sampler consisting of a 5 L Niskin bottle. Upon recovery of the bottles, water samples were filtered through 0.2 μm Millipore® filters, using a Teflon tubing apparatus. The filtration was done immediately on board, and samples were always transported within 8 h to the laboratory. Filtered samples were acidified to pH 1–2 with HNO3 (Merck ULTRAPUR®) and stored in hot-acid-washed polyethylene bottles.
Seafloor sediments were sampled with a Van Veen bucket in the same stations where seawater and suspended materials in the water column were collected.
In order to increase the signal/noise ratio in the studied seawaters, for yttrium and lanthanides analyses 1000 mL of each sample was pre-concentrated with a CHELEX 100® (100–200 mesh) ion exchange resin:
• pH value of each seawater sample was set to 6.0 ± 0.1 with CH3COONH4, and an aliquot of each seawater sample passed on an 8-cm-long column filled with CHELEX-100 100–200 mesh previously cleaned and conditioned.
• REY were eluted with 5 mL of HNO3 3.5 M, giving a 100-fold enrichment factor. Details of the procedures are reported in the literature.
Details on matrix:
Sediment and suspended matter samples taken from several sampling locations in the western Gulf of Thailand.
Details on test conditions:
Seawater and suspended matter samples were taken at 0.5 m depth and/or at greater depths between 5 and 18 m.
Computational methods:
Concentrations of the element under consideration analysed in suspended matter were divided by dissolved concentrations of the element analysed in filtered seawater sampled at the same sampling location (including same depth) to obtain Kp values.
For sediment-water Kp values, the concentration analysed in the sediment sample was divided by the dissolved concentration in filtered seawater from the greatest sampling depth.
Phase system:
suspended matter-water
Type:
log Kp
Value:
>= 4.75 - <= 7.78 L/kg
Remarks on result:
other: range for all samples
Phase system:
suspended matter-water
Type:
log Kp
Value:
6.61 L/kg
Remarks on result:
other: mean value all samples

Station number Gd (nmol/L) Gd (mg/L) Gd in SPM (mg/kg) Kp SPM (L/kg) log Kp
128a 0,18219 2,86E-05 58,823 2053203,425 6,31
129a 0,03307 5,20E-06 31,477 6052969,492 6,78
130a 0,41494 6,52E-05 149,992 2298752,102 6,36
131a 0,03847 6,05E-06 57,285 9469522,428 6,98
132a 0,31351 4,93E-05 2,785 56491,50531 4,75
133a 0,36089 5,67E-05 47,617 839066,7816 5,92
134a 0,40223 6,33E-05 21,557 340818,5376 5,53
135a 0,20541 3,23E-05 265,277 8212726,511 6,91
138a 0,51447 8,09E-05 51,124 631937,4844 5,80
140a 0,02791 4,39E-06 79,472 18107715,07 7,26
141a 0,02671 4,20E-06 58,746 13986651,66 7,15
142a 0,03561 5,60E-06 72,942 13026118,94 7,11
143a 0,11256 1,77E-05 36,324 2052196,433 6,31
144a 0,74881 1,18E-04 28,295 240296,4797 5,38
145a 0,12051 1,90E-05 27,127 1431489,039 6,16
146a 0,23148 3,64E-05 86,543 2377539,922 6,38
147a 0,02338 3,68E-06 27,198 7397786,757 6,87
148a 0,02576 4,05E-06 68,213 16839556,03 7,23
149a 0,01106 1,74E-06 15,846 9111164,137 6,96
150a 0,02696 4,24E-06 255,957 60374906,24 7,78
151a 0,07568 1,19E-05 8,199 688952,2279 5,84
152a 0,03302 5,19E-06 NA
153a 0,05628 8,85E-06 12,451 1406887,886 6,15
128b 0,03339 5,25E-06 64,453 12275411,61 7,09
129b 0,02607 4,10E-06 176,317 43009312,7 7,63
140b 0,01876 2,95E-06 26,966 9140985,963 6,96
141b 0,02385 3,75E-06 128,571 34281829 7,54
147b 0,10334 1,63E-05 95,223 5859799,393 6,77
148b 0,03466 5,45E-06 1,644 301635,6025 5,48
150b 0,0531 8,35E-06 NA
128c 0,02385 3,75E-06 168,249 44861465,24 7,65
129c 0,09857 1,55E-05 113,695 7335098,587 6,87
130c 0,07758 1,22E-05 77,172 6325856,36 6,80
131c 0,09094 1,43E-05 12,923 903686,3873 5,96
140c 0,06455 1,02E-05 NA
141c 0,0868 1,36E-05 56,692 4153473,072 6,62
142c 0,11797 1,86E-05 114,628 6179146,351 6,79
148c 0,05151 8,10E-06 132,667 16378748,13 7,21
149c 0,04706 7,40E-06 9,736 1315642,785 6,12
150c 0,04738 7,45E-06 235,495 31607924,56 7,50
151c 0,13196 2,08E-05 44,677 2153034,764 6,33
152c 0,06582 1,04E-05 53,752 5193332,106 6,72
Conclusions:
In this study, samples of suspended matter and (filtered) seawater were taken from various sampling sites in the western Gulf of Thailand and analysed for Gd. Log Kp suspended-matter values were calculated from the results obtained for paired samples and ranged between 4.75 and 7.78 L/kg, the mean being 6.61 L/kg.
Endpoint:
adsorption / desorption, other
Remarks:
multitracer experiment
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
Reference:
Composition 0
Qualifier:
no guideline followed
Principles of method if other than guideline:
Multitracer experiment. The adsorption of elements on model samples of marine particulates, including deep-sea and near-shore sediments, was studied.
GLP compliance:
no
Type of method:
other: multitracer experiment
Media:
sediment
Test material information:
Composition 1
Radiolabelling:
yes
Remarks:
radioactive multitracers are used
Test temperature:
25°C
Analytical monitoring:
yes
Details on sampling:
The suspension was shaken in an 8-shape mode with a shaker at 25° C. After centrifugation, a portion of the supernatant solution was pipetted.
Details on matrix:
Matrix 1
COLLECTION AND STORAGE
- Geographic location: deep-sea sediment Penrhyn Basin (12°26.44'S, 157°57.20'W, depth 5351 m)
- Storage conditions: in artificial seawater (storage 2 mg/cm³ artificial seawater), pH of suspension adjusted to 7.5

Matrix 2
COLLECTION AND STORAGE
- Geographic location: near-shore sediment Suruga Bay (34°44.52.'N, 169°27.05'E, depth ca. 600 m)
- Storage conditions: in artificial seawater (storage 2 mg/cm³ artificial seawater), pH of suspension adjusted to 7.5
Details on test conditions:
TEST CONDITIONS
10 cm3 of artificial sea water and 0.01 cm3 of a multitracer solution were put into a polyethylene bottle. After the pH was adjusted to 7.5 with a 1 M Na2CO3 solution, the adsorbent suspension was added. Resulting concentrations of adsorbent were 0.1, 0.05 and 0.01 mg/cm3. pH of suspension was readjusted to 7.5 when necessary.

Artifical seawater containing 23.94 g NaCl and 0.196 g NaHCO3 / 1000 cm3 water was used.

TEST SYSTEM
- Type, size and further details on reaction vessel: polyethylene bottle.
- Amount of soil/sediment/sludge and water per treatment: 10 cm3 artificial seawater + 0.01 cm3 of a multitracer solution + 0.1, 0.05 or 0.01 mg adsorbent/cm3.
- Suspension was shaken in a 8-shape mode with a shaker at 25°C.
- To reach equilibrium, 1-2 days of shaking was needed (not further specified for Gd).
Computational methods:
Kads = (Aads/m)/(Asoln/V) = ((Ai - Af)/Af)(V/m)
Aads = radioactivity in the adsorbent after adsorption equilibrium
Asoln = radioactivity in the solution after adsorption equilibrium
V = volume of the solution (cm3)
m = amount of adsorbent (g)
Ai = radioactivity in the solution before adsorption equilibrium
Af = radioactivity in the solution after adsorption equilibrium
Phase system:
sediment-water
Type:
log Kp
Value:
5.69 L/kg
Temp.:
25 °C
pH:
7.5
Matrix:
deep-sea sediment
Phase system:
sediment-water
Type:
log Kp
Value:
5.23 L/kg
Temp.:
25 °C
pH:
7.5
Matrix:
near-shore sediment
Conclusions:
In this multitracer experiment, the log Kp for gadolinium for deep-sea and near-shore sediment in artificial seawater was determined to be 5.69 and 5.23 L/kg, respectively.
Endpoint:
adsorption / desorption, other
Remarks:
field study
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
Reference:
Composition 0
Qualifier:
no guideline followed
Principles of method if other than guideline:
Sediment, pore water, suspended matter, and water samples were taken in the Forsmark area, Baltic Sea, and analysed for Gd.
GLP compliance:
not specified
Type of method:
other: field study
Media:
other: sediment and suspended matter
Test material information:
Composition 1
Radiolabelling:
no
Test temperature:
between 2.3 and 12.3°C during sampling
Analytical monitoring:
yes
Details on sampling:
- Location and timing: all samples collected between 12-20 April 2005 in the bay between the north side of the islands of Stor and Lill-Tixlan, between the Forsmark nuclear power station and the town of Öregrund, NW Baltic Proper.
- Integrated water samples (10 L) collected from 0-4 m depth using a metal-free pump.
- Particulate organic matter in the water column was sampled through filtration of the water samples.
- Sediment: Kajak cores were taken at 7-8 m depth and sliced into two sections (0-3 cm and 3-6 cm).
- Pore water was extracted by centrifugation (20 min at 4500 rpm) from sediment samples.
Details on matrix:
no details reported
Details on test conditions:
field test
Computational methods:
Partitioning coefficients were calculated by dividing Gd concentration in solid phase by Gd concentration in water (L/kg).
Kpsuspended matter-water as well as Kpsediment-pore water were calculated (the latter for upper layer (0-3 cm) and lower layer (3-6 cm)).
Phase system:
suspended matter-water
Type:
log Kp
Value:
5.11 L/kg
Remarks on result:
other: Concentrations in filtered water were below the detection limit, therefore the detection limit was used as aquatic Gd concentration.
Phase system:
solids-water in sediment
Type:
log Kp
Value:
3.45 L/kg
Remarks on result:
other: Concentrations in sediment and pore water of upper sediment layer (0-3 cm) were used.
Details on results (Batch equilibrium method):
For the lower sediment layer (3-6 cm), a log Kpsediment-pore water of 4.15 L/kg was obtained (Gd concentrations in pore water were however below the detection limit, consequently the detection limit was used for calculation of the log Kp).
Conclusions:
In this study, water, suspended matter, sediment, and pore water samples were taken in the Forsmark area, Baltic Sea, and analysed for gadolinium. The log Kpsuspended matter-water was calculated to be 5.11 L/kg, using the detection limit as aquatic gadolinium concentration since gadolinium was not detectable in the water phase. The log Kpsediment-pore water for the upper sediment layer (0-3 cm) was determined to be 3.45 L/kg.
Endpoint:
adsorption / desorption, other
Remarks:
field study
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
Reference:
Composition 0
Qualifier:
no guideline followed
Principles of method if other than guideline:
Sediment and pore water samples were collected from two rivers which receive wastewater from urban Hanoi (Vietnam) and analysed for Gd.
GLP compliance:
not specified
Type of method:
other: field study
Media:
sediment
Test material information:
Composition 1
Radiolabelling:
no
Test temperature:
not reported
Analytical monitoring:
yes
Details on sampling:
- Sediment samples collected from To Lich and Kim Nguu rivers, both of which receive wastewater from urban Hanoi, Vietnam. Samples collected from three sites in both rivers with a stainless steel Kajak core sediment sampler equipped with a polymethylmethacrylat inner liner with an inner diameter of 46 mm. Three replicates were collected from each site. Core samples were subdivided into sections 0-10cm, 10-20cm, 20-30cm. Sediment samples were dried at 45°C until constant weight, passed through a 2 mm stainless steel sieve and pulverised in an agate mortar.
- Pore water was extracted from sediment samples: sediment from 0-10cm depth was transferred to polypropylene büchner funnel with 25 µm mesh nylon filter and a minimum of 15 mL pore water was extracted under suction of 10 kPa. Pore water was filtered through a 0.45 µm nylon filter (Millipore) and acidified with 0.1 mL 70% HNO3 (Baker Instra-Analysed).
Details on matrix:
- % organic carbon: 1.2-5.3% in To Lich river samples, 1.8-10.6% in Kim Nguu rivers
- pH of pore water was 7.4-8.1
- redox potential of pore water was -257 to -185 mV
Details on test conditions:
field study
Computational methods:
Partitioning coefficients were calculated by dividing Gd concentration in sediment by Gd concentration in pore water (L/kg).
Phase system:
solids-water in sediment
Type:
log Kp
Value:
>= 5.15 - <= 6.32 L/kg
% Org. carbon:
>= 1.2 - <= 10.6
Remarks on result:
other: range for all paired samples, precipitation processes may have been involved
Details on results (Batch equilibrium method):
The organic carbon concentration seemed to have the most important effect on sediment Gd concentrations.
Conclusions:
In this study, samples of sediment and pore water were taken along two rivers receiving wastewater from Hanoi, Vietnam, and analysed for Gd. Log Kpsediment-pore water values of 5.15 to 6.32 L/kg were reported. However, reliability is restricted, because precipitation processes may have been involved in sediment next to sorption processes, yielding overestimated partitioning coefficients. Suggest using only the lowest boundary for further data analysis.
Endpoint:
adsorption / desorption, other
Remarks:
field study and laboratory study with field samples
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
Reference:
Composition 0
Qualifier:
no guideline followed
Principles of method if other than guideline:
Field study in which Gd concentrations were determined in both surface water, pore water, sediment, and suspended matter. Samples were taken from 6 sampling locations in the Rhine-Meuse estuary in The Netherlands. Further, also a lab study was performed using field samples.
GLP compliance:
not specified
Type of method:
other: both field study and laboratory study using field samples
Media:
other: sediment and suspended matter
Test material information:
Composition 1
Radiolabelling:
no
Test temperature:
Field sampling: no temperature range given.
Laboratory experiment: 15 °C
Analytical monitoring:
yes
Details on sampling:
Field sampling:
- Surface-water samples, suspended solids, and sediments (through 25-cm-deep, box-core sampling) were collected during June and July 1997 at six locations in the Rhine-Meuse estuary.
- Sampling locations: Nieuwe Maas, Nieuwe Maas, First Petroleum Harbour, Botlekhaven, Northsea Loswal Noord, and Northsea Terheide 30. Locations 1, 2, 6 are relatively clean. Locations 3, 4 are directly influenced by industrial discharges, and location 5 is a disposal site for sediments that are contaminated through industrial discharges.
- Surface water samples were 0.45 µm filtered.
- Pore water samples were obtained by positive-pressure filtration (0.45 µm).
Lab study (location 2 sediment and water):
- Samples taken after 10 days.
Details on matrix:
- Sampling: see above.
- Organic carbon (%) median (range): 5.9 (4.0-24.2) in suspended solids of the six locations, 1.94 (0.08-3.82) in sediments of the six locations, 2.13 (0.88-2.81) for the sediments used in the lab study.
Details on test conditions:
Field study: no specific test conditions.
Laboratory study:
For every assay, two acid-rinsed polystyrene aquaria (replicates) were filled with sediments (1750 g wet weight) and seawater (4 L) from the appropriate location (2). Standard conditions: pH = 8.1, salinity 30 g/L, no addition of complexing agents, exposure time 10 d.
Further assays were conducted with diversified conditions:
- varying pH: 7.1, 7.7, 8.1 and 8.5;
- varying salinity: 10, 20 and 30 g/L
- addition of complexing agents: 500 mg H(PO4)2-, 400 µg F-
Computational methods:
Indicative adsorption coefficients could only be calculated using the median Gd concentrations reported for the six locations and the laboratory study in pore water, surface water, sediments and suspended solids.
Phase system:
sediment-water
Type:
log Kp
Value:
ca. 5.47 L/kg
Remarks on result:
other: calculated using median values for field samples (sediment and surface water)
Phase system:
solids-water in sediment
Type:
log Kp
Value:
ca. 5.43 L/kg
Remarks on result:
other: calculated using median values for field samples (sediment and pore water)
Phase system:
suspended matter-water
Type:
log Kp
Value:
ca. 5.63 L/kg
Remarks on result:
other: calculated using median values for field samples (suspended matter and surface water)
Phase system:
sediment-water
Type:
log Kp
Value:
ca. 5.5 L/kg
Remarks on result:
other: calculated using median values for laboratory study samples (sediment and surface water)
Phase system:
solids-water in sediment
Type:
log Kp
Value:
ca. 4.75 L/kg
Remarks on result:
other: calculated using median values for laboratory study samples (sediment and pore water)
Adsorption and desorption constants:
see above
Statistics:
Median values used for Kp calculation, hence Kp values only indicative. Paired values for aqueous and solid phase not reported.
Conclusions:
In this study, gadolinium concentrations were determined in surface water, pore water, sediment and suspended solids of six locations in the Rhine-Meuse estuary (the Netherlands) as well as in a lab study using field samples of one of the six locations. Only medians and ranges were reported, therefore, only indicative adsorption coefficients could be calculated using the median values. Log Kp values for sediment-surface water were 5.47 L/kg (field) and 5.5 L/kg (laboratory). Log Kp values for sediment-pore water were 5.43 L/kg (field) and 4.75 L/kg (laboratory). The log Kp value for suspended solids-surface water was 5.63 L/kg (field).
Endpoint:
adsorption / desorption, other
Remarks:
field study
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
Reference:
Composition 0
Qualifier:
no guideline followed
Principles of method if other than guideline:
Field study in which gadolinium concentrations were determined in surface water and sediment. Samples were taken from 15 different stations located in 4 different estuarine areas in Japan.
GLP compliance:
not specified
Remarks:
field study, results reported in scientific literature, no information on GLP
Type of method:
other: field study
Media:
sediment
Test material information:
Composition 1
Radiolabelling:
no
Test temperature:
Field water samples: 17.4-27.0°C with a geomean of 22.1°C
Analytical monitoring:
yes
Details on sampling:
Sampling locations:
- Near the mouth of the Mabechi River off Aomori (August 2007). Estuarine area located on the North Pacific side of Honshu. Water depth up to 60 m. 3 sampling stations.
- Near the mouth of the Mogami River off Yamagata (August 2007). Estuarine area located on the Japan sea side of Honshu. Water depth up to 55 m. 3 sampling stations.
- Near the mouth of the Kuma River off Kumamoto (November 2007). Semiclosed estuarine area located in the Yatsushiro Sea on the North Pacific Ocean side of Kyushu. Water depth up to 30 m. 3 sampling stations.
- Near the mouth of the Yura River off Kyoto (seasonal differences investigated - July, September, November 2007). Semiclosed estuarine area located in the SW part of Honshu at Wakasa Bay on the Japan Sea. Water depth up to 55 m. July: 3 sampling stations. September: 4 sampling stations. November: 2 sampling stations.

Water samples:
In each of the 4 estuarine areas, bottom water samples were taken 1-15 m above the seafloor at 2–4 stations that were located at different distances from the mouth of each river.
- Water was collected in acid-cleaned, Teflon-coated, 5-L horizontal Niskin X sampling bottles (General Oceanics).
- For metal analysis samples were filtered (< 0.2 µm fraction) with a precleaned 0.2 µm pore size capsule cartridge-type polytetrafluoroethylene filter (Advantec) connected to a sampling bottle spigot and then the water sample was gravity-filtered into a precleaned 250-mL low density polyethylene bottle. The filtrates were acidified with 0.1 mL of 68% superpure grade HNO3 (Tama Chemicals, AA-100) per 100 mL. The acidified solutions (pH < 2) were kept in a refrigerator (5°C) until the analyses for dissolved elements were done.

Sediment samples:
Surface sediments were collected at the same sampling point as for the water collection in the estuarine areas using an Eckmann bottom corer (Miyamoto Riken Inc., A-15). The surface sediment samples were transferred to polyethylene bags and stored in a refrigerator. The raw surface sediments were dried at room temperature, and then sieved (2 mm) to remove large particles and shell fragments before being dried at 105°C to a constant weight, which indicated the complete removal of moisture. Afterwards, the dried samples were transferred to glass bottles and stored in a dark place until analysis.
Details on matrix:
Both sandy and muddy sediments were observed, color from brown over dark brown and very dark grey to black.
Water content of sediments between 26 and 70% (geometric mean 42%).
Loss on ignition between 2.1 and 9.3% (geometric mean 4.8%).
Details on test conditions:
Field study.
Temperature range of water samples: 17.4-27°C
Salinity range of water samples: 31.9-34.2 g/L
pH range of water samples: 8.1-8.4
DO (dissolved oxygen) concentration in water samples: 6.7-8.3 mg/L
SPM (suspended particulate matter) concentration 0.1-4.1 mg/L
DOC (dissolved organic carbon) concentration: 0.82-1.36 mg/L
Computational methods:
Kp = Cs/Cb
where Cs (g/kg) and Cb (g/L) represent the total element concentration in surface sediment and the dissolved element concentration in estuarine water, respectively.
In the publication, Cs was multiplied by a factor of 0.2 because in the International Atomic Energy Agency (IAEA) Technical Report Series 422, 20% of the total concentration of each element in sediment was defined as exchangeable fraction with the aqueous phase. Because under REACH, such a factor is not applied in the calculation of Kp values, the values reported in the study were divided by 0.2.
Phase system:
sediment-water
Type:
log Kp
Value:
>= 5.6 - <= 6.48 L/kg
Remarks on result:
other: range for all paired samples
Phase system:
sediment-water
Type:
log Kp
Value:
6.21 L/kg
Remarks on result:
other: mean for all paired samples
Conclusions:
In this study, samples of sediment and water were taken from 15 sampling stations in 4 Japanese estuaria and analysed for gadolinium. Log Kp values ranged from 5.60 to 6.48 L/kg, the mean being 6.21 L/kg.
Endpoint:
adsorption / desorption, other
Remarks:
field study
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
Reference:
Composition 0
Qualifier:
no guideline followed
Principles of method if other than guideline:
Sediment, pore water, and surface water samples were taken at five locations in The Netherlands. These samples were analysed for Gd.
GLP compliance:
not specified
Type of method:
other: field study
Media:
sediment
Test material information:
Composition 1
Radiolabelling:
no
Test temperature:
Temperature at sampling occasions between 18 and 21°C.
Analytical monitoring:
yes
Details on sampling:
Five locations in The Netherlands, four of them in highly industrialised region around city of Rotterdam. All sampling sites in catchment of Rhine and Meuse rivers. 1. Veluwemeer, 2. Botlekpark, 3. Kralingse Plas, 4. Nieuwe Maas, 5. Charlois.
Samples were taken in August and September 2000.
Surface water samples (n=3) 0.45 µm filtered.
Pore water samples (n=3) were extracted in situ using Rhizon soil moisture samplers (MOM type, Eijkelkamp Agrisearch Equipment, Giesbeek, The Netherlands).
Sediment samples (n=3) were collected with a bottom sampler according to Ekman-Birge (Hydro-bios, Kiel, Germany).
Details on matrix:
Average pH of sampling locations at time of sampling was between 7.30 and 8.72. Quite similar for pore water (between 6.92 and 7.55).
No characteristics given for sediment.
Details on test conditions:
Field study.
Computational methods:
Kp sediment values were calculated dividing concentration in sediment (mg/kg) by concentrations in either surface water or pore water (mg/L).
This was done separately for the < 2 mm sediment fraction and the < 0.063 mm sediment fraction.
Phase system:
sediment-water
Type:
log Kp
Value:
>= 5.18 - <= 6 L/kg
Remarks on result:
other: range derived from Figure 11 (< 2-mm sediment fraction)
Phase system:
solids-water in sediment
Type:
log Kp
Value:
>= 5 - <= 5.3 L/kg
Remarks on result:
other: range derived from Figure 12 (< 2-mm sediment fraction)
Concentration of test substance at end of adsorption equilibration period:
The lanthanide concentrations measured in the < 0.063-mm sediment fraction were similar as those in the < 2-mm sediment fraction for three out of the five sampled locations. For the locations Nieuwe Maas and Veluwemeer, the < 0.063-mm sediment fraction however contained higher lanthanide concentrations than the sediment fraction < 2 mm. These locations are those with the lowest concentrations of lanthanides measured in the < 2-mm fraction and the highest in the < 0.063-mm fraction. This is due to exclusion of the relatively high sand fraction of these sediments, which for the most part is > 0.063 mm and contains low lanthanide concentrations.
Conclusions:
In this study, sediment, surface water, and pore water samples were taken at five locations in The Netherlands in the Rhine-Meuse catchment. Gd was determined in all samples and log Kp sediment-surface water was reported (in figures) to range from 5.18 to 6 L/kg, whereas the log Kp sediment-pore water was reported (also in figures) to range from 5 to 5.3 L/kg.
Endpoint:
adsorption / desorption, other
Remarks:
microcosm study
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
Reference:
Composition 0
Qualifier:
no guideline followed
Principles of method if other than guideline:
A microcosm study was performed in which concentrations of Gd in water and sediment were also monitored.
GLP compliance:
not specified
Type of method:
other: microcosm study
Media:
sediment
Test material information:
Composition 1
Radiolabelling:
no
Test temperature:
Water temperature 22 +/- 1°C
Analytical monitoring:
yes
Details on sampling:
- Water and sediment sampled at 12 and 24 h and 2, 4, 8, 12 and 16 d.
- Water was filtered 0.45 µm.
- Sediment samples were washed with deionised water and dried by air. Then 0.5 g of dried sample was digested with Na2O2 at 700°C and passed through cation-exchange columns.
- Final solutions of all samples brought to 5 mL with 7% HCl.
Details on matrix:
Sediment from eutrophic lake (Xuanwu Lake, Nanjing, China).
Sediment samples were dried by air before adding into aquarium.
Details on test conditions:
Microcosm study using water and sediment from a typical eutrophic lake - Xuanwu Lake in Nanjing, China.
Organisms: duckweeds (Sperollela polyrrhiza), crustaceans (Daphnia magna), goldfish (Carassius auratus), shellfish (Bellamya aeruginosa).
After the system has equilibrated for 1 week, the experiment was initiated by spiking mixed REEs stock solutions (a mixture of five REEs with 1.00 mg/mL each: La(NO3)3.6H2O, CeCl3.7H2O, SmCl3.nH2O, Gd2O3 and Y2O3) into the aquarium to 1 mg/L.
The pH was kept at 6.5-6.8 because rare earth elements would precipitate under alkaline conditions.
Computational methods:
Kp sediment values were calculated dividing concentrations in sediment (mg/kg) by concentrations in water (mg/L).
Phase system:
sediment-water
Type:
log Kp
Value:
2.6 L/kg
Temp.:
22 °C
Remarks on result:
other: Value after 16 days
Details on results (Batch equilibrium method):
Distribution of Gd was 82.01% in sediment, 16.97% in water, and 1.02% in biota.
Conclusions:
In this microcosm study, water and sediment Gd concentrations were monitored for up to 16 days. Based on the concentrations reported for 16 days, a log Kp sediment of 2.6 L/kg could be calculated. Data were taken from figures.
Endpoint:
adsorption / desorption, other
Remarks:
field study and lab study with field samples
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
secondary literature
Reference:
Composition 0
Composition 0
Qualifier:
no guideline followed
Principles of method if other than guideline:
The concentration of gadolinium in water and sediment at state of equilibrium was measured in laboratory tests and in the field and Kp values were calculated.
GLP compliance:
no
Type of method:
other: field study and laboratory experiment with field samples
Media:
sediment
Test material information:
Composition 1
Radiolabelling:
no
Test temperature:
no data
Analytical monitoring:
yes
Details on sampling:
Samples of sediment, pore water and surface water were taken at Nieuwe Maas, Rhine estuary, The Netherlands.
Samples in the laboratory study were taken after 10 days.
All water samples 0.45 µm filtered.
Details on matrix:
- Details on collection location: Nieuwe Maas, Rhine estuary, The Netherlands, three different collection times.
- pH at time of collection: 8-8.5
- Organic carbon (%): 0.88, 2.17 and 2.77 % at different sample collection times
Details on test conditions:
Laboratory experiment: duration time 10 d
Computational methods:
Kp sediment-surface water and Kp sediment-pore water distribution coefficients were calculated using measured concentrations in solid and aqueous phase.
Phase system:
sediment-water
Type:
log Kp
Value:
5.58 L/kg
Remarks on result:
other: laboratory (sediment and surface water)
Phase system:
sediment-water
Type:
log Kp
Value:
5.71 L/kg
Remarks on result:
other: field (sediment and surface water)
Phase system:
solids-water in sediment
Type:
log Kp
Value:
4.74 L/kg
Remarks on result:
other: laboratory (sediment and pore water)
Phase system:
solids-water in sediment
Type:
log Kp
Value:
5.42 L/kg
Remarks on result:
other: field (sediment and pore water)

Sneller et al. stated, that the differences between the laboratory and the field derived data are probably due to disturbance and subsequent oxidation of the sediments in the laboratory experiments, causing relatively high concentrations in the pore water. In addition, increased decay of organic material in the disturbed sediments, involving reduction-processes, may contribute to release of REEs from sediment. For these reasons, field derived partition coefficients are preferred over laboratory derived values for calculation of MACs (maximum acceptable concentrations).

Furthermore, when evaluating the partitioning data one must keep in mind that pH, the presence of negative counterions and the concentration of dissolved organic carbon (DOC) in the (pore-) water strongly influence the concentration of REEs in solution. When pH, DOC concentrations and negative counterion concentrations are high, a large part of the total dissolved REE concentrations may not represent ´true´ partitioning.

Conclusions:
In this study, adsorption of gadolinium to sediment was evaluated by determining gadolinium in sediment, pore water, and surface water sampled in the field and after 10 days of using sediment/water samples in a study in the laboratory. The obtained log Kp sediment values were 5.58 and 5.71 L/kg when based on sediment and surface water concentrations in laboratory and field, respectively, and 4.74 and 5.42 L/kg when based on sediment and pore water concentrations in laboratory and field, respectively.
Endpoint:
adsorption / desorption, other
Remarks:
read across data
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 gadolinium to particulate matter is used from experiments performed in the laboratory (e.g., multitracer experiment of Chen et al., 1996; microcosm study of Yang et al., 1999) as well as from field or mixed field/laboratory experiments, in which field samples of particulate matter and surface/pore water were analysed for Gd. In the microcosm study of Yang et al. (1999), Gd2O3 was used as test item. In the multitracer study, Gd in a multitracer solution was used as 'test item'. In the remaining studies, there was no specific test item, as Gd present in field samples was analysed. Therefore, in theory, all studies should be considered as read across studies. Nevertheless, regardless of the test item (specific test item added or Gd present in field samples), an elemental approach was followed to cover this endpoint, lumping the data from all available studies.
Reason / purpose:
read-across source
Related information:
Composition 1
Reason / purpose:
read-across source
Related information:
Composition 1
Reason / purpose:
read-across source
Related information:
Composition 1
Reason / purpose:
read-across source
Related information:
Composition 1
Reason / purpose:
read-across source
Related information:
Composition 1
Reason / purpose:
read-across source
Related information:
Composition 1
Reason / purpose:
read-across source
Related information:
Composition 1
Reason / purpose:
read-across source
Related information:
Composition 1
Reason / purpose:
read-across source
Related information:
Composition 1
Test material information:
Composition 1
Phase system:
sediment-water
Type:
log Kp
Value:
>= 2.6 - <= 6.48 L/kg
Remarks on result:
other: range of log Kp values for sediment-surface water and sediment-pore water obtained in the read across studies
Phase system:
suspended matter-water
Type:
log Kp
Value:
>= 4.75 - <= 7.78 L/kg
Remarks on result:
other: range of log Kp values for sediment-surface water and sediment-pore water obtained in the read across studies

Description of key information

A total of nine studies was used in a weight of evidence approach to cover the endpoint. Data were available for suspended matter and sediment, however, not for soil. The following final key values were retained: a log Kp of 5.78 L/kg for suspended matter-water and a log Kp of 5.15 L/kg for sediment-water.

Key value for chemical safety assessment

Other adsorption coefficients

Type:
other: log Kp suspended matter-water
Value in L/kg:
5.78

Other adsorption coefficients

Type:
other: log Kp sediment-water
Value in L/kg:
5.15

Additional information

In total, nine studies were selected as useful for covering the adsorption/desorption endpoint using a weight of evidence approach. Data were available for sediment and suspended matter (no studies identified for soil) and will be further discussed below.

 

For suspended matter three studies were identified as useful. Moermond et al. (2001) analysed samples from several locations along the Rhine-Meuse estuary. Based on gadolinium concentrations measured in suspended matter and water, a log Kp of 5.63 L/kg was calculated. Kumblad and Bradshaw (2008) reported a log Kp value of 5.11 L/kg, based on gadolinium concentrations measured in water and suspended matter sampled in the Forsmark area, Baltic Sea. Finally, Censi et al. (2005) analysed samples of suspended matter and (filtered) seawater taken from various sampling sites in the western Gulf of Thailand. Log Kp suspended-matter values were calculated from the results obtained for paired samples and ranged between 4.75 and 7.78 L/kg, the mean being 6.61 L/kg. Because there is a limited amount of values available, the arithmetic mean was calculated of the values from Moermond et al. (2001), Kumblad and Bradshaw (2008) and the mean for all paired samples analysed by Censi et al. (2005), resulting in an average log Kp value of 5.78 L/kg, which is considered as the key value for characterising distribution between suspended matter and water.

 

For sediment eight studies were included in the weight of evidence approach. Based on data from the study of Moermond et al. (2001) for sediment, surface water and pore water, log Kp values could be calculated ranging from 4.75 to 5.5 L/kg. Sneller et al. (2000) reported log Kp values obtained by Stronkhorst and Yland (1998) of 4.74 to 5.71 L/kg for samples taken from the field and a laboratory study using field samples. More specifically values of 4.74 to 5.42 L/kg were obtained for sediment-pore water and 5.58 to 5.71 L/kg for sediment-surface water. Weltje et al. (2002) investigated gadolinium distribution between sediment and surface water or pore water in samples taken along the Rhine-Meuse catchment (the Netherlands) and reported log Kp values of 5.18 to 6.0 L/kg for sediment-surface water and 5.0 to 5.3 L/kg for sediment-pore water. Marcussen et al. (2008) sampled sediment and pore water along two rivers receiving wastewater from Hanoi, Vietnam. Log Kp values for sediment-pore water for these samples were reported to be between 5.15 and 6.32 L/kg. However, because precipitation processes may have been involved in sediment next to sorption processes, partitioning coefficients may have been overestimated. Therefore only the lower boundary of the reported range was included in the calculation of a key value for partitioning between sediment and water. Kumblad and Bradshaw (2008) reported a log Kp for upper sediment of 3.45 L/kg based on results for samples taken in the Forsmark area, Baltic Sea. In the study of Takata et al. (2010), samples of sediment and water were taken from 15 sampling stations in 4 Japanese estuaria and analysed for gadolinium. Log Kp values ranged from 5.6 to 6.48 L/kg, the mean being 6.21 L/kg. Chen et al. (1996) performed a multitracer experiment to investigate the adsorptive behavior of gadolinium and other lanthanides to marine sediments and obtained log Kp values for gadolinium of 5.69 and 5.23 L/kg for deep-sea and near-shore sediment in artificial seawater, respectively. Finally, the microcosm study of Yang et al. (1999) yielded a log Kp sediment of 2.6 when using the data for the 16-d sampling point. To determine a final key value, a single average (arithmetic mean) log Kp value was retained for each study. Pore water-based and surface water-based data were however not lumped, individual average values (arithmetic mean) were retained for this. The 10th, 50th and 90th percentile of the retained values was 3.45, 5.15 and 5.65, respectively. The median of 5.15 was taken as key log Kp.