Cerium trinitrate

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

bioaccumulation in aquatic species: fish

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:

No analytical measurements of the rare earth element in the water media were performed, which yields a lower reliability score, however, the study is useful in a weight-of-evidence approach.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Bioconcentration and elimination of five light rare earth elements (La, Ce, Pr, Nd and Sm (as mixture)) were investigated in carp. The study was performed according to similar principles as those laid down in test guidelines for bioaccumulation.

GLP compliance:

no

Radiolabelling:

no

Details on sampling:

- Sampling intervals/frequency for test organisms and medium:
* uptake study: 3, 8, 15, 29, 36 and 43 d
* elimination study: 1, 3, 8, 18 and 36 d

Vehicle:

no

Details on preparation of test solutions, spiked fish food or sediment:

- stock solution was added into the aquaria with stirring
- stock solution was a mixture of 6 light Rare Earth Elements, tested as their nitrates: Ce(NO3)3*6H2O, La(NO3)3*nH2O, SmCI3*6H2O, PrNd(NO3)6*nH2O.

Test organisms (species):

Cyprinus carpio

Details on test organisms:

TEST ORGANISM
- Common name: carp
- Age at study initiation (mean and range, SD): first year juveniles
- Length at study initiation (length definition, mean, range and SD): 7.0 cm
- Weight at study initiation (mean and range, SD): 3.7 g
- Feeding during test: fish were fed dry food before each renewal

ACCLIMATION
- Acclimation period: 10 d

Route of exposure:

aqueous

Test type:

semi-static

Water / sediment media type:

natural water: freshwater

Total exposure / uptake duration:

43 d

Total depuration duration:

36 d

Hardness:

53-60 mg CaCO3/L

Test temperature:

11-14 °C

pH:

6.4-7.4

Dissolved oxygen:

> 7.0 mg/L

TOC:

no data

Salinity:

not applicable

Details on test conditions:

TEST SYSTEM
- Test vessel: 60 L glass aquarium with 30 L test solution
- Renewal rate of test solution: a volume of 20 L of test solution was renewed every other day
uptake study:
- No. of organisms per vessel (test concentration): 60
- No. of organisms per vessel (control): 10
- No. of vessels per concentration (replicates): 2
- No. of vessels per control / vehicle control (replicates): 2
elimination study
- No. of organisms per vessel (test concentration): 30
- No. of vessels per concentration (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: tap water
- Chlorine: 7.0-8.5 mg/L
- Total alkalinity: 1.15-2.15 mmol/L
- Conductivity: 170 (mOhm*cm)-1

OTHER TEST CONDITIONS
- Adjustment of pH: yes (modified to 6.0 with HNO3 and NaOH
- Test concentration: chosen concentration was close to the concentration in a natural aquatic environment

ELIMINATION EXPERIMENTS:
When equilibrium was reached, 30 fishes of each test aquarium were placed in non-contaminated water. This was renewed three times a week to monitor REEs elimination according to the same experimental protocols as during the bioconcentration study.

Nominal and measured concentrations:

Mixture of:
0.3 mg/L Lanthanum
0.27 mg/L Cerium
0.29 mg/L Neodymium
0.06 mg/L Praseodymium
0.25 mg/L Samarium

Reference substance (positive control):

not specified

Details on estimation of bioconcentration:

- toxicokinetic study within 43 d: equilibrium was reached or approached
- BCF was calculated as the concentration of test substance in fish tissue (mg/kg ww)) divided by the nominal concentration of test substance in test
water (mg/L).

Type:

BCF

Value:

0.22 - 1.46

Basis:

organ w.w.

Remarks:

muscle

Calculation basis:

steady state

Remarks on result:

other: time of plateau: see table 2

Remarks:

Conc. in environment / dose: 0.27 mg Ce/L

Type:

BCF

Value:

1.12 - 5.94

Basis:

organ w.w.

Remarks:

skeleton

Calculation basis:

steady state

Remarks on result:

other: time of plateau: see table 2

Remarks:

Conc. in environment / dose: 0.27 mg Ce/L

Type:

BCF

Value:

5.83 - 14.8

Basis:

organ w.w.

Remarks:

gills

Calculation basis:

steady state

Remarks on result:

other: time of plateau: see table 2

Remarks:

Conc. in environment / dose: 0.27 mg Ce/L

Type:

BCF

Value:

44 - 804

Basis:

organ w.w.

Remarks:

internal organs

Calculation basis:

steady state

Remarks on result:

other: time of plateau: see table 2 / internal organs reflect the normal transit of the substance rather than indication of bioaccumulation

Remarks:

Conc. in environment / dose: 0.27 mg Ce/L

Details on kinetic parameters:

Elimination experiments:
The elimination process of light REEs in gills, muscle and skeleton were similar and could be divided into two periods: a fast elimination period followed by slower loss period. After 8-day elimination experiment, the elimination rate became slow and equilibria were reached. This elimination pattern suggests that the light REEs which bioconcentrated in fish tissues may exist in two forms, one is unbound REEs which accounted for more than 50%-70% of total tissue REEs concentrations, another is the REEs which are bound tightly in fish tissues. Half-lives of the unbound form and the bound form that fitted mathematically a two-compartment model, are given in table 3.
The elimination process of REEs in internal organs can also be divided into two periods, in the first period the concentrations of REEs increased and reached the maximum values at the end of the second day. In the second period, REEs were lost from internal organs and the kinetics of elimination can be described by the one-compartment model. Half-life (d) for Cerium: 8.66 d with R=0.98 (R= correlation coefficient).

Only data for cerium are shown here.

Table 1: Background values of cerium in Cyprinus carpio

tissue	Ce concentration (mg/kg wet weight)
gills	--
muscle	0.10
skeleton	--
internal organs	0.87

Large variations of BCFs are observed for different tissues, the order of bioconcentration factors is: internal organs >> gills > skeleton > muscle. The BCF value in internal organs was higher than that reported for muscles, skeleton and gills. This was expected considering that the alimentary tract reflects normal transit of the substance. For this reason, this observation cannot be considered as an indication of bioaccumulation.

Table 2: Variations of BCFs of cerium in Cyprinus carpio exposed to mixed REEs at pH 6.0 (only data for cerium shown here)

tissue	Bioconcentration Factor (L/kg wet weight)
	3 d	8 d	15 d	29 d	36 d	43 d
gills	5.83	13.0	7.81	13.4	14.8	12.8
muscle	0.60	1.01	0.82	1.46	0.49	0.22
skeleton	1.49	2.02	4.00	4.52	1.12	5.94
internal organs	128	163	387	804	44.0	608

Table 3: The biological half-lives and percentage of cerium in different tissues of Cyprinus carpio

tissue	Unbound form		Bound form
	Half-live d	%	Half-live d	%	R*
skeleton	0.24	47.5	23.9	52.4	0.89
gills	0.13	83.7	25.7	16.3	0.98
muscle	0.14	85.2	25.7	14.8	0.98

R*: The correlation coefficient of releasing equations according to a two-compartment model

Conclusions:

In this study, carp (Cyprinus carpio) were exposed to a mixture of light REEs (among which Ce, at 0.27 mg Ce/L) for 43 days. BCF values were calculated for skeleton, gills, muscle, and internal organs, ranging from 1.12 to 5.94, 5.83 to 14.8, 0.22 to 1.46 and 44 to 804 L/kg ww, respectively. The BCF value in internal organs was higher than that reported for muscles, skeleton and gills. This was expected considering that the alimentary tract reflects the normal transit of the substance. For this reason, this observation cannot be considered as an indication of bioaccumulation. Based on the BCF values calculated for other organs (i.e., skeleton, gills, muscle), cerium presents a low potential for bioaccumulation in carp.

Reference 2

Endpoint:

bioaccumulation in aquatic species, other

Remarks:

all types of organisms studied in the source studies for read across

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

The endpoint aquatic bioaccumulation is covered by a series of read across studies, among which several field studies (in which cerium was analysed in field samples) as well as laboratory studies performed with water soluble cerium salts other than Ce(NO3)3 (e.g., CeCl3, as well as a non-identified Ce(+IV) salt). The rationale for read across is described to detail in the read across document attached to IUCLID Section 13. One study (Sun et al., 1996) was performed with Ce(NO3)3 but for completeness the results of this study have been included in the derivation of the overall ranges and the key bioaccumulation factor for fish presented here below.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Type:

BCF

Value:

>= 1.72 - <= 17 200 L/kg

Basis:

whole body w.w.

Calculation basis:

other: steady state assumed

Remarks on result:

other: overall range for aquatic algae and cyanobacteria and aquatic macrophytes

Type:

BAF

Value:

>= 2.75 - <= 24 000 L/kg

Basis:

whole body w.w.

Calculation basis:

other: steady state assumed

Remarks on result:

other: overall range for aquatic invertebrates

Type:

BAF

Value:

>= 1.25 - <= 2 000 L/kg

Basis:

whole body w.w.

Calculation basis:

other: steady state assumed

Remarks on result:

other: overall range for fish (whole body)

Type:

BMF

Value:

<= 1 dimensionless

Basis:

whole body d.w.

Calculation basis:

other: steady state assumed

Remarks on result:

other: BMF values for fish

Key result

Type:

BAF

Value:

16 L/kg

Basis:

whole body w.w.

Calculation basis:

other: steady state assumed

Remarks on result:

other: key BAF value derived for fish - worst case value since all data were included, i.e. results for whole body as well as internal organs

Reference 3

Endpoint:

bioaccumulation in aquatic species, other

Remarks:

fish and bivalves

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:

Reliability with limitations (Klimisch 2) because not all information seems to be reported on the field study set-up. It is important to note that field studies provide snapshots in time of environmental concentrations of polluents and therefore cannot entirely guarantee steady state in the sampled organisms. For this reason, BAF values resulting from such studies have to be considered with caution.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Samples of water and organisms were taken from coastal and open waters and analysed for cerium.

GLP compliance:

not specified

Radiolabelling:

no

Details on sampling:

200-mL samples of water were collected with a submersible pump and polyethylene hoses directly into polyethylene tanks, except for the ocean samples that were collected with a large-volume sampler.
No details reported on sampling of marine organisms. Only edible portions were analysed.
Sampling locations: Chesapeake Bay and Chincoteague Bay

Vehicle:

no

Test organisms (species):

other: Roccus saxatilus, Crassostrea virginica, and Mya arenaria

Details on test organisms:

Roccus saxatilis: striped bass (fish).
Crassostrea virginica: Eastern oyster (bivalve).
Mya arenaria: soft-shell clam (bivalve).

Route of exposure:

aqueous

Test type:

field study

Water / sediment media type:

natural water: marine

Hardness:

not reported

Test temperature:

not reported

pH:

not reported

Dissolved oxygen:

not reported

TOC:

not reported

Salinity:

not reported

Details on test conditions:

Field samples taken from surface water and organisms (fish and bivalves).

Nominal and measured concentrations:

Not clearly reported for the exact sampling locations.

Reference substance (positive control):

no

Details on estimation of bioconcentration:

BAF values were calculated based on Ce concentrations measured in organisms and Ce concentrations measured in water samples (L/kg ww).

Type:

BAF

Value:

< 20 L/kg

Basis:

organ w.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: edible portions of striped bass (Roccus saxatilus)

Remarks:

Conc. in environment / dose: not clearly reported

Type:

BAF

Value:

60 - 80 L/kg

Basis:

organ d.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: edible portions of Eastern oyster (Crassostrea virginica)

Remarks:

Conc. in environment / dose: not clearly reported

Type:

BAF

Value:

1 000 L/kg

Basis:

organ w.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: edible portions of soft-shell clam (Mya arenaria)

Remarks:

Conc. in environment / dose: not clearly reported

Validity criteria fulfilled:

not specified

Conclusions:

In this study, samples were taken from surface water and organisms from two coastal areas (Chesapeake Bay and Chincoteague Bay) and analysed for Ce. The publication reports a concentration factor (BAF) of < 20 L/kg ww for striped bass (Roccus saxatilus), ca. 60-80 L/kg ww for Eastern oyster (Crassostrea virginica) and 1000 L/kg ww for soft-shell clam (Mya arenaria).

Reference 4

Endpoint:

bioaccumulation in aquatic species: algae / cyanobacteria

Remarks:

periphyton

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:

Reliable with restrictions (Klimisch 2) because data were only presented in figures and because the concentration factor reported was calculated using a combination of the concentration in sediment and water. It is important to note that field studies provide snapshots in time of environmental concentrations of polluents and therefore cannot entirely guarantee steady state in the sampled organisms. For this reason, BCF values resulting from such studies have to be considered with caution.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Samples were taken of surface water and periphyton of the Sava River and analysed for cerium. In the Sava River environment radionuclides such as 144Ce are present in higher than background concentrations since the Chernobyl accident in 1986.

GLP compliance:

not specified

Details on sampling:

Periphyton samples were collected manually.
Water samples were collected with plastic bottles and acidified with 0.1N HNO3.

Vehicle:

no

Test organisms (species):

other: periphyton

Details on test organisms:

not reported - periphyton

Route of exposure:

aqueous

Test type:

field study

Water / sediment media type:

natural water: freshwater

Hardness:

not reported

Test temperature:

not reported

pH:

not reported

Dissolved oxygen:

not reported

TOC:

not reported

Salinity:

not applicable

Details on test conditions:

not reported, field study

Nominal and measured concentrations:

not reported

Details on estimation of bioconcentration:

The reported concentration ratio was calculated dividing the radionuclide concentration in the periphyton by the sum of the radionuclide concentration in sediment and water. The ratio was expressed in mg/g.

Type:

BCF

Value:

ca. 1 000 L/kg

Basis:

whole body d.w.

Calculation basis:

steady state

Remarks on result:

other: 144Ce in periphyton divided by sum of 144Ce in water and sediment, recalculated assuming all 144Ce in water

Remarks:

Conc. in environment / dose: not reported

Validity criteria fulfilled:

not specified

Conclusions:

In this study, 144Ce was analysed in water, sediment and periphyton samples taken from the Sava River, which is affected by the Chernobyl accident in 1986. Concentration ratios were reported dividing 144Ce in periphyton by the sum of 144Ce in sediment and water. When assuming all 144Ce in sediment and water was present in the water, a BCF of 1000 L/kg dw could be calculated.

Reference 5

Endpoint:

bioaccumulation in aquatic species, other

Remarks:

algae, aquatic plants, and aquatic invertebrates

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:

It is important to note that field studies provide snapshots in time of environmental concentrations of polluents and therefore cannot entirely guarantee steady state in the sampled organisms. For this reason, BCF/BAF values resulting from such studies have to be considered with caution.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Field study in which samples were taken of water, sediment, and organisms in the Forsmark area, Baltic Sea, and analysed for cerium (and other elements).

GLP compliance:

not specified

Radiolabelling:

no

Details on sampling:

- The selected study area is Tixlan Bay in the Forsmark area (NW Baltic Proper) which is located within the area of interest for the potential localisation of a geological repository for spent nuclear fuel.
- Water samples: integrated 10-L samples collected at 0-4 m depth using a metal-free pump.
- Phytoplankton: depth-integrated water sample (from 1 m above the bottom to the surface, usually about 0-4 m), pumped into two nested plankton nets with mesh sizes 60 µm and 20 µm. The fraction retained on the 20 µm net was washed out into plastic containers. In the lab, the samples were concentrated by sieving them on a 20 µm plastic sieve.
- Zooplankton: water was pumped into nested 100 µm and 60 µm nets. A depth-integrated sample was taken from ca. 1 m above the seabed up to the surface. The retained fractions were pooled. Further concentration was done in the lab over a 50 µm sieve.
- Benthic microalgae: stones collected in shallow (1-2 m) water, surface organic film brushed off using a toothbrush, resulting suspension sieved through 400 µm and 20 µm plastic sieves.
- Macroalgae, macrophytes and phytobenthic fauna: manual collection.
- Soft bottom benthos: surface sediment (0-10 cm) collected at 7-8 m depth using plastic scoop and mesh bags and Ekman grabs.
- Fish: fish nets laid in eastern part of the bay on two consecutive evenings and collected the next morning.
- Sediment: Kajak cores were taken at 7-8 m depth. Cores were sliced shortly afterwards into two sections (0-3 cm, 3-6 cm).
- Pore water: extracted by centrifugation from sediment samples (20 min at 4500 rpm).

Vehicle:

no

Test organisms (species):

other: phyto/zooplankton, benthic microalgae, aquatic macrophytes, aquatic invertebrates, fish

Details on test organisms:

- phyto/zooplankton
- benthic microalgae
- aquatic macrophytes (Fucus vesiculosus, Pilayella littoralis, Potamogeton pectinatus)
- aquatic invertebrates (Theodoxus fluviatilis, Idothea spp., Cerastoderma glaucum, Macoma baltica
- fish (Rutilus rutilus (roach), Gymnocephalus cernuus (ruffe), Osmerus eperlanus (smelt))

Route of exposure:

aqueous

Test type:

field study

Water / sediment media type:

natural water: brackish

Hardness:

not reported

Test temperature:

Temperature during sampling was between 2.3 and 12.3°C.

pH:

Roughly between 7.95 and 8.05 during sampling.

Dissolved oxygen:

> 14.7 mg O2/L during sampling

TOC:

not reported

Salinity:

Roughly between 5.21 and 5.23 ppt during sampling.

Details on test conditions:

field study

Nominal and measured concentrations:

average measured concentration of Ce was 0.01 µg Ce/L

Details on estimation of bioconcentration:

BCF values (bioconcentration factor) and BAF values (bioaccumulation factors) were calculated dividing element concentration in organism by element concentration in water (L/kg ww).

Type:

BCF

Value:

20 L/kg

Basis:

whole body w.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: phytoplankton

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BCF

Value:

2 800 L/kg

Basis:

whole body w.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: benthic microalgae

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BCF

Value:

1 800 L/kg

Basis:

whole body w.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: Fucus vesiculosus (brown macroalga)

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BCF

Value:

270 L/kg

Basis:

whole body w.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: Pilayella littoralis (brown macroalga)

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BCF

Value:

930 L/kg

Basis:

whole body w.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: Potamogeton pectinatus (Sago pondweed)

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BAF

Value:

2 900 L/kg

Basis:

whole body w.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: zooplankton

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BAF

Value:

6 400 L/kg

Basis:

whole body w.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: Theodoxus fluviatilis (river nerite - snail)

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BAF

Value:

640 L/kg

Basis:

whole body w.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: Idothea spp. (isopod)

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BAF

Value:

11 000 L/kg

Basis:

whole body w.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: Macoma baltica (Baltic clam)

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BAF

Value:

4 200 L/kg

Basis:

whole body w.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: Cerastoderma glaucum (lagoon cockle)

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Details on results:

In this endpoint study record only the BCFs for algae and macroflora and the BAFs for aquatic invertebrates were reported.

Conversion factors for conversion of wet to dry weight and vice versa are reported in the publication. In the following table these conversion factors are shown as well as the BCF/BAF values in L/kg.

Organism / group of organisms	% dw	BCF / BAF (L/kg dw)
Phytoplankton	2.07	966
Benthic microalgae	5.76	48611
Fucus vesiculosus	20.74	8679
Pilayella littoralis	8.17	3305
Potamogeton pectinatus	11.12	8363
Zooplankton	0.83	349398
Theodoxus fluviatilis	33.00	19394
Idothea spp.	16.68	3837
Macoma baltica	32.95	33384
Cerastoderma glaucum	30.73	13667

Conclusions:

In this study, water and organisms were sampled from locations in the Forsmark area, and analysed for Ce. In this endpoint study record the results were shown for algae and macroflora and for aquatic invertebrates. For algae and macroflora BCF values ranged from 20 to 2800 L/kg ww (corresponding to a range of 966 to 48611 L/kg dw, using ww-dw conversion factors reported in the publication). For aquatic invertebrates BAF values were obtained between 640 and 11000 L/kg ww (corresponding to a range of 3837 to 349398 L/kg dw, using ww-dw conversion factors reported in the publication).

Reference 6

Endpoint:

bioaccumulation in aquatic species, other

Remarks:

aquatic invertebrates and fish

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:

It is important to note that field studies provide snapshots in time of environmental concentrations of polluents and therefore cannot entirely guarantee steady state in the sampled organisms. For this reason, BMF values resulting from such studies have to be considered with caution.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Field study in which samples were taken of water, sediment, and organisms in the Forsmark area, Baltic Sea, and analysed for cerium (and other elements).

GLP compliance:

not specified

Radiolabelling:

no

Details on sampling:

- The selected study area is Tixlan Bay in the Forsmark area (NW Baltic Proper) which is located within the area of interest for the potential localisation of a geological repository for spent nuclear fuel.
- Water samples: integrated 10-L samples collected at 0-4 m depth using a metal-free pump.
- Phytoplankton: depth-integrated water sample (from 1 m above the bottom to the surface, usually about 0-4 m), pumped into two nested plankton nets with mesh sizes 60 µm and 20 µm. The fraction retained on the 20 µm net was washed out into plastic containers. In the lab, the samples were concentrated by sieving them on a 20 µm plastic sieve.
- Zooplankton: water was pumped into nested 100 µm and 60 µm nets. A depth-integrated sample was taken from ca. 1 m above the seabed up to the surface. The retained fractions were pooled. Further concentration was done in the lab over a 50 µm sieve.
- Benthic microalgae: stones collected in shallow (1-2 m) water, surface organic film brushed off using a toothbrush, resulting suspension sieved through 400 µm and 20 µm plastic sieves.
- Macroalgae, macrophytes and phytobenthic fauna: manual collection.
- Soft bottom benthos: surface sediment (0-10 cm) collected at 7-8 m depth using plastic scoop and mesh bags and Ekman grabs.
- Fish: fish nets laid in eastern part of the bay on two consecutive evenings and collected the next morning.
- Sediment: Kajak cores were taken at 7-8 m depth. Cores were sliced shortly afterwards into two sections (0-3 cm, 3-6 cm).
- Pore water: extracted by centrifugation from sediment samples (20 min at 4500 rpm).

Vehicle:

no

Test organisms (species):

other: phytoplankton, benthic microalgae, aquatic macrophytes, aquatic invertebrates, fish

Details on test organisms:

- phytoplankton
- benthic microalgae
- aquatic macrophytes (Fucus vesiculosus, Pilayella littoralis, Potamogeton pectinatus)
- aquatic invertebrates (Theodoxus fluviatilis, Idothea spp., Cerastoderma glaucum, Macoma baltica
- fish (Rutilus rutilus (roach), Gymnocephalus cernuus (ruffe), Osmerus eperlanus (smelt))

Route of exposure:

aqueous

Test type:

field study

Water / sediment media type:

natural water: brackish

Hardness:

not reported

Test temperature:

Temperature during sampling was between 2.3 and 12.3°C.

pH:

Roughly between 7.95 and 8.05 during sampling.

Dissolved oxygen:

> 14.7 mg O2/L during sampling

TOC:

not reported

Salinity:

Roughly between 5.21 and 5.23 ppt during sampling.

Details on test conditions:

field study

Nominal and measured concentrations:

average measured concentration of Ce was 0.01 µg Ce/L

Details on estimation of bioconcentration:

BMF values (biomagnification factors) were calculated dividing element concentration in organism by element concentration in food (kg/kg dw based).

Type:

BMF

Value:

0 L/kg

Basis:

whole body d.w.

Calculation basis:

steady state

Remarks on result:

other: Idothea spp. (isopod) feeding on Fucus vesiculosus in pathway I

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BMF

Value:

0 L/kg

Basis:

whole body d.w.

Calculation basis:

steady state

Remarks on result:

other: Gymnocephalus cernuus (Ruffe, benthic fish), feeding on Isothea spp. in pathway I

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BMF

Value:

1 L/kg

Basis:

whole body d.w.

Calculation basis:

steady state

Remarks on result:

other: Osmerus eperlanus (Smelt, carnivore fish), feeding on Ruffe in pathway I

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BMF

Value:

0 L/kg

Basis:

whole body d.w.

Calculation basis:

steady state

Remarks on result:

other: Macoma baltica (Baltic clam), feeding on sediment in pathway II

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BMF

Value:

0 L/kg

Basis:

whole body d.w.

Calculation basis:

steady state

Remarks on result:

other: Gymnocephalus cernuus (Ruffe, benthic fish), feeding on Macoma baltica in pathway II

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BMF

Value:

1 L/kg

Basis:

whole body d.w.

Calculation basis:

steady state

Remarks on result:

other: Osmerus eperlanus (Smelt, carnivore fish), feeding on Ruffe in pathway II

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BMF

Value:

374 L/kg

Basis:

whole body d.w.

Calculation basis:

steady state

Remarks on result:

other: zooplankton, feeding on phytoplankton in pathway III

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BMF

Value:

0 L/kg

Basis:

whole body d.w.

Calculation basis:

steady state

Remarks on result:

other: Rutilus rutilus (Roach, planktivore fish), feeding on zooplankton in pathway III

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BMF

Value:

1 L/kg

Basis:

whole body d.w.

Calculation basis:

steady state

Remarks on result:

other: Osmerus eperlanus (Smelt, carnivore fish), feeding on Roach in pathway III

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Details on results:

In this endpoint study record the obtained BMFs (biomagnification factors) were reported for three different foodchains:
I. Fucus vesiculosus (brown macroalga) - Idothea spp. (isopod) - Gymnocephalus cernuus (Ruffe, benthic fish) - Osmerus eperlanus (Smelt, carnivore fish).
II. Sediment - Macoma baltica (Baltic clam) - Gymnocephalus cernuus (Ruffe, benthic fish) - Osmerus eperlanus (Smelt, carnivore fish).
III. Phytoplankton - zooplankton - Rutilus rutilus (Roach, planktivore fish) - Osmerus eperlanus (Smelt, carnivore fish).

Validity criteria fulfilled:

not specified

Conclusions:

In this study, water and organisms were sampled from locations in the Forsmark area, and analysed for Ce. In this endpoint study record the biomagnification factors (BMF) for organisms in three different food pathways were reported. No biomagnification occurs, except for zooplankton feeding on phytoplankton in the third food pathway (BMF = 374 kg/kg, dw based). However, this biomagnification did not continue further in the foodchain, as the next organisms in food pathway III showed BMF values of 0 and 1 (planktivore and carnivore fish, respectively).

Reference 7

Endpoint:

bioaccumulation in aquatic species: fish

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:

It is important to note that field studies provide snapshots in time of environmental concentrations of polluents and therefore cannot entirely guarantee steady state in the sampled organisms. For this reason, BAF values resulting from such studies have to be considered with caution.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Field study in which samples were taken of water, sediment, and organisms in the Forsmark area, Baltic Sea, and analysed for cerium (and other elements).

GLP compliance:

not specified

Radiolabelling:

no

Details on sampling:

- The selected study area is Tixlan Bay in the Forsmark area (NW Baltic Proper) which is located within the area of interest for the potential localisation of a geological repository for spent nuclear fuel.
- Water samples: integrated 10-L samples collected at 0-4 m depth using a metal-free pump.
- Phytoplankton: depth-integrated water sample (from 1 m above the bottom to the surface, usually about 0-4 m), pumped into two nested plankton nets with mesh sizes 60 µm and 20 µm. The fraction retained on the 20 µm net was washed out into plastic containers. In the lab, the samples were concentrated by sieving them on a 20 µm plastic sieve.
- Zooplankton: water was pumped into nested 100 µm and 60 µm nets. A depth-integrated sample was taken from ca. 1 m above the seabed up to the surface. The retained fractions were pooled. Further concentration was done in the lab over a 50 µm sieve.
- Benthic microalgae: stones collected in shallow (1-2 m) water, surface organic film brushed off using a toothbrush, resulting suspension sieved through 400 µm and 20 µm plastic sieves.
- Macroalgae, macrophytes and phytobenthic fauna: manual collection.
- Soft bottom benthos: surface sediment (0-10 cm) collected at 7-8 m depth using plastic scoop and mesh bags and Ekman grabs.
- Fish: fish nets laid in eastern part of the bay on two consecutive evenings and collected the next morning.
- Sediment: Kajak cores were taken at 7-8 m depth. Cores were sliced shortly afterwards into two sections (0-3 cm, 3-6 cm).
- Pore water: extracted by centrifugation from sediment samples (20 min at 4500 rpm).

Vehicle:

no

Test organisms (species):

other: phyto/zooplankton, benthic microalgae, aquatic macrophytes, aquatic invertebrates, fish

Details on test organisms:

- phytoplankton/zooplankton
- benthic microalgae
- aquatic macrophytes (Fucus vesiculosus, Pilayella littoralis, Potamogeton pectinatus)
- aquatic invertebrates (Theodoxus fluviatilis, Idothea spp., Cerastoderma glaucum, Macoma baltica
- fish (Rutilus rutilus (roach), Gymnocephalus cernuus (ruffe), Osmerus eperlanus (smelt))

Route of exposure:

aqueous

Test type:

field study

Water / sediment media type:

natural water: brackish

Hardness:

not reported

Test temperature:

Temperature during sampling was between 2.3 and 12.3°C.

pH:

Roughly between 7.95 and 8.05 during sampling.

Dissolved oxygen:

> 14.7 mg O2/L during sampling

TOC:

not reported

Salinity:

Roughly between 5.21 and 5.23 ppt during sampling.

Details on test conditions:

field study

Nominal and measured concentrations:

average measured concentration of Ce was 0.01 µg Ce/L

Details on estimation of bioconcentration:

BAF values (bioaccumulation factors) were calculated dividing element concentration in organism by element concentration in water (L/kg ww).

Type:

BAF

Value:

2 000 L/kg

Basis:

whole body w.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: Gymnocephalus cernuus (Ruffe) - whole fish samples

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BAF

Value:

160 L/kg

Basis:

whole body w.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: Osmerus eperlanus (Smelt) - whole fish samples

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BAF

Value:

110 L/kg

Basis:

whole body w.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: Rutilus rutilus (Roach) - whole fish samples

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BAF

Value:

4.6 L/kg

Basis:

whole body w.w.

Remarks:

without internal organs

Calculation basis:

other: assumed steady state

Remarks on result:

other: Gymnocephalus cernuus (Ruffe) - mixed fish slices (without internal organs)

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BAF

Value:

2.7 L/kg

Basis:

whole body w.w.

Remarks:

without internal organs

Calculation basis:

other: assumed steady state

Remarks on result:

other: Osmerus eperlanus (Smelt) - mixed fish slices (without internal organs)

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Type:

BAF

Value:

1.8 L/kg

Basis:

whole body w.w.

Remarks:

without internal organs

Calculation basis:

other: assumed steady state

Remarks on result:

other: Rutilus rutilus (Roach) - mixed fish slices (without internal organs)

Remarks:

Conc. in environment / dose: average 0.01 µg Ce/L

Details on results:

In this endpoint study record only the BAFs for fish are shown.

Validity criteria fulfilled:

not specified

Conclusions:

In this study, water and organisms were sampled from locations in the Forsmark area, and analysed for Ce. In this endpoint study record the results were shown for fish. When whole fish were analysed, BAF values ranged from 110 to 2000 L/kg ww, the highest factor being obtained for Ruffe (Gymnocephalus cernuus), a benthic omnivore which lives in close contact with the sediment. When however mixed fish slices were analysed, from which internal organs were removed, the BAF values ranged from 1.8 to 4.6 L/kg ww. In order to conclude on the bioaccumulation potential for fish, it is more relevant to look at the BAF values obtained after removal of internal organs as presence of cerium in these organs represents the normal transit of the substance and is therefore not indicative of bioaccumulation.

Reference 8

Endpoint:

bioaccumulation in sediment species: invertebrate

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:

Calculated BCF/BAF values are however only indicative (K2, reliable with restrictions) because they were calculated based on median values. For the values derived from the field study, it is important to note that field studies provide snapshots in time of environmental concentrations of polluents and therefore cannot entirely guarantee steady state in the sampled organisms. For this reason, BAF values resulting from such studies have to be considered with caution.

Principles of method if other than guideline:

The aim of the study was to quantify the variation in estuarine lanthanide solid/water distribution, speciation, and bioaccumulation. The latter was studied in the amphipod Corophium volutator under field and laboratory conditions.

GLP compliance:

no

Radiolabelling:

no

Details on sampling:

Field study:
- Surface water, suspended solids, sediments (through 25-cm deep, box-core sampling), and amphipods (where present) were collected during June and July 1997 at six locations in the Rhine-Meuse estuary at turn of tide in the North Sea. Surface and pore water samples were obtained by positive-pressure fltration (0.45 µm, Gelman, Ann Arbor, MI, USA).
Lab study:
Standard bioassays: after 10 d samples were taken of sediment, pore water, surface water, and biota
Bioassay with varying duration (0, 0.5, 1, 2, 10 and 20 d) were used to evaluate whether time of exposure was sufficient to reach equilibrium.

Location 1: Nieuwe Maas
Location 2: Nieuwe Maas
Location 3: First Petroleum harbour
Location 4: Botlekhaven
Location 5: Northsea, Loswal Noord
Location 6: Northsea, Terheide 30

Vehicle:

no

Details on preparation of test solutions, spiked fish food or sediment:

Surface-water samples, suspended solids, sediments (through 25-cm-deep, box-core sampling), and amphipods (where present) were collected during June and July 1997 at six locations in the Rhine-Meuse estuary at turn of tide and in the North Sea. These locations in the western Netherlands represented a gradient in salinity (S) from location 1 to 6 as well as a gradient in pollution. Locations 1, 2, and 6 are relatively clean. Locations 3 and 4 are directly influenced by industrial (i.e., lanthanide) discharges, and location 5 is a disposal site for sediments that are contaminated through industrial
discharges.
Location 2 sediment and water was used in the laboratory bioassays.

Test organisms (species):

other: Corophium volutator

Details on test organisms:

Field study:
- Amphipods (C. volutator) were gathered where present.
Lab study:
- Randomly picked individuals of C. volutator obtained from a non contaminated intertidal area.

Route of exposure:

other: sediment + aquatic

Test type:

other: static laboratory study and field study

Water / sediment media type:

natural sediment: marine

Total exposure / uptake duration:

10 d

Hardness:

no data available

Test temperature:

Median during lab study: 15°C - Median during field study: 19°C

pH:

Median pH in surface water during lab study: 8.0
Median pH in surface water during field study: 7.9
Lab bioassay with varying pH: 7.1, 7.7, 8.1 and 8.5

Dissolved oxygen:

no data available

TOC:

only data given for DOC in pore water of the six locations: 15.6 mg/L (range 6.7 - 25.3 mg/L)

Salinity:

Standard bioassays: 30 g/L
Lab bioassay with varying salinity: 10, 20 and 30 g/L

Details on test conditions:

Bioassays were conducted according to the protocol described by Ciarelli et al., 1997.
For every bioassay, two acid-rinsed polystyrene aquaria (replicates) were filled with sediments (1750 g wet weight) and seawater (4 L) from the appropriate location. After 24 h of adaptation, 400 randomly picked individuals of C. volutator obtained from a non contaminated intertidal area were added (no information is given about the background concentration in the biota). After an exposure period of 10 d (standard bioassay), one replicate was separated into a water phase and a sediment phase, including the biota. The C. volutator from the other replicate were sieved out. Dead animals were not included in the biota sample for chemical analysis. Biota, sediment, and water were frozen until further analysis.
Bioassays at different conditions:
1. To determine if the time of exposure was sufficient to reach equilibrium, a time series was conducted with standard environmental conditions (pH 8.1, salinity 30 g/L).
2. The effects of carbonate complexation on lanthanide bioavailability were studied by varying pH with aeration by CO2-manipulated air.
3. To assess the effects of chloride and sulfate complexation, salinity was varied by diluting the seawater with demineralized water.
4. The effects of gypsum disposal were mimicked through addition of phosphate and fluoride. (500 mg H(PO4)2-, 400 µg F)
5. For the resuspension experiment, the effects of turbulence associated with dredging were simulated as follows: First, the overlying water was carefully transferred to another aquarium. Subsequently, 20-cm3 portions of the remaining sediment layer, including the biota, were gently added to the water in the new aquarium. This procedure was repeated until all sediments were transferred. (Conditions according to the standard bioassay: pH 8.1, salinity 30g/L)

Nominal and measured concentrations:

Contaminated sediment and seawater in the laboratory:
Surface water: 758E-12 mol Ce/L (180E-12 - 1758E-12 mol Ce/L)
Pore water: 3463E-12mol Ce/L (1518E-12 - 26282E-12 mol Ce/L)
Sediment: 361 µmol Ce/kg (293 - 458 µmol Ce/kg)
Contaminated sediment and seawater in the field:
Surface water: 269E-12 mol Ce/L (149E-12 - 872E-12 mol Ce/L)
Pore water: 501E-12 mol Ce/L (344E-12 - 1419E-12 mol Ce/L)
Sediment: 367 µmol Ce/kg (89 - 1899 µmol Ce/kg)

Reference substance (positive control):

no

Details on estimation of bioconcentration:

BAF values (field study) were calculated dividing Ce concentration in C. volutator (mg/kg dw) by Ce concentration in surface water or pore water (mg/L).
BCF values (lab study) were calculated in a similar way.

Type:

BCF

Value:

17 500 L/kg

Basis:

whole body d.w.

Calculation basis:

steady state

Remarks on result:

other: Corophium volutator, laboratory experiment, BCF based on surface water concentration

Remarks:

Conc. in environment / dose: 0.106 µg Ce/L

Type:

BCF

Value:

3 840 L/kg

Basis:

whole body d.w.

Calculation basis:

steady state

Remarks on result:

other: C. volutator, laboratory experiment, BCF based on pore water concentration

Remarks:

Conc. in environment / dose: 0.485 µg Ce/L

Type:

BAF

Value:

6 320 L/kg

Basis:

whole body d.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: based on field samples of surface water and C. volutator

Remarks:

Conc. in environment / dose: 0.038 µg Ce/L

Type:

BAF

Value:

3 390 L/kg

Basis:

whole body d.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: based on field samples of pore water and C. volutator

Remarks:

Conc. in environment / dose: 0.070 µg Ce/L

Cerium concentrations and biota sediment accumulation factor (BSAF) values at six locations in the Rhine-Meuse estuary (The

Netherlands) compared with conditions during laboratory bioassays:

	field		laboratory
	median	range	median	range
Surface water (pmol/L)	269	149-872	758	180-1758
Pore water (pmol/L)	501	344-1419	3463	1518-26282
Sediment (µmol/kg)	367	89-1899	361	293-458
Suspended solids (µmol/kg)	535	53-760
C. volutator (mmol/kg d.w.)	1.7	1.0-5.1	13.3	10.1-23.9
BSAF*	0.078	0.037-0.139	0.369	0.258-0.786

* Defined as the concentration in biota (mol/kg dry wt) divided by concentration in sediment (mol/kg).

The BSAFs for field locations are generally much lower than those for the laboratory bioassays, except for the t = 0 bioassay. Salinity and pH had no clear effect on BSAF. In contrast, lanthanide BSAF values were higher after resuspension, especially for lanthanum, and after addition of phosphate and fluoride (paired t-test, p , 0.01). The exposure-time experiment showed a rapid uptake during the first day, after which no clear further uptake was observed. The authors stated that at t = 0, the low BSAF relates to the background value of lanthanides in the uncontaminated biota.

Validity criteria fulfilled:

not specified

Conclusions:

In this study, samples of surface water, pore water, sediment, and biota (Corophium volutator) were taken in the field at six locations in the Netherlands and analysed for Ce, yielding BAF values of 6320 L/kg (based on surface water) and 3390 L/kg (based on pore water) (both dw based). These BAF values were calculated using median concentrations, i.e., to be used as indicative values (not based on paired concentrations). A lab study exposing C. volutator from uncontaminated sites for 10 days to field samples of sediment and surface water yielded BCF values of 17500 L/kg (based on surface water) and 3840 L/kg (based on pore water) (dw based, also based on medians).

Reference 9

Endpoint:

bioaccumulation in sediment species: invertebrate

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Remarks:

Scientific review listing available data on several endpoints. BAF values reported in lumped way for La, Ce, Nd. It is important to note that field studies provide snapshots in time of environmental concentrations of polluents and therefore cannot entirely guarantee steady state in the sampled organisms. For this reason, BAF values resulting from such studies have to be considered with caution.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Field experiment. BAFs were reported for bivalves, worms and crustaceans in the Dutch Rhine estuary area.

GLP compliance:

not specified

Radiolabelling:

no

Details on sampling:

no data

Vehicle:

no

Details on preparation of test solutions, spiked fish food or sediment:

- 6 locations in the Rhine estuary and the North Sea: Brienneoord, Nieuwe Maas 1006, 1e Petroleumhaven, Botlek, Loswal Noord, Ter Heijde 30
- Brienneoord and Niewe Maas 1006: freshwater samples, the other locations: brackish and salt water samples
- the samples were taken in 1997, three samples per location

Test organisms (species):

other: Crustaceans, worms and bivalves (Corbicula fluminea)

Details on test organisms:

TEST ORGANISMS
- field collection of species with numerous occurrence at the different sample sites
- van Brienneoord: Corophium multisetosum (a few Gammarus trigrinus, one Palaemon longirostris), Corbicula fluminea
- Nieuwe Maas 1006: Corophium multisetosum, Nereis diversicolor, Corbicula fluminea
- 1e Petroleumhaven: Corbicula fluminea
- Botlek: Corophium multisetosum, Nereis diversicolor
- Ter Heijde 30: Urothoe poseidonis (and a few other crustacean taxa); Nephtys cirrosa (and a few other worm taxa)

Route of exposure:

aqueous

Test type:

field study

Water / sediment media type:

natural sediment: marine

Hardness:

2.4 - 24.4 meq/L CaCO3

Test temperature:

no data

pH:

7.5 - 8.2

Dissolved oxygen:

no data

TOC:

no data

Salinity:

0.22 - 33 mg/L

Details on test conditions:

Exposure in the field, field samples analysed.

Nominal and measured concentrations:

Measured Ce concentrations:
in sediment: 12.5 - 183.3 mg/kg dw
in pore water: 0.0482 - 0.1988 µg/L
in surface water: 0.0209 - 0.1221 µg/L

Reference substance (positive control):

no

Details on estimation of bioconcentration:

- Monitoring data
- BAF calculated by dividing concentrations of the element measured in the organisms (mg/kg dw) by concentrations of the element measured in the water (mg/L).

Type:

BAF

Value:

ca. 15 000 - 50 000

Basis:

whole body d.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: Corbicula fluminea (bivalves), field data, lumped BAF range for La, Ce, Nd

Remarks:

Conc. in environment / dose: concentration in pore water: 0.0482 - 0.1988 µg/L

Type:

BAF

Value:

ca. 8 000 - 120 000

Basis:

whole body d.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: worms, field data, lumped BAF range for La, Ce, Nd

Remarks:

Conc. in environment / dose: concentration in pore water: 0.0482 - 0.1988 µg/L

Type:

BAF

Value:

ca. 10 000 - 40 000

Basis:

whole body d.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: crustaceans, field data, lumped BAF range for La,Ce,Nd

Remarks:

Conc. in environment / dose: concentration in pore water: 0.0482 - 0.1988 µg/L

Differences in BAF of salt and fresh water samples were not observed.

Values derived from field studies may not be comparable to those from classical laboratory methods. The analytical data may vary considerably in the field and give only one point in time. The organisms could have been exposed via different routes of exposure and there was no way to determine if the concentrations really reflect steady state or a momentary peak ion exposure.

Nevertheless the values are in good agreement with other investigations, which showed that cerium has a potential to bioaccumulate in aquatic organisms. The reported BAF values were rather high, which may be partly due to the fact that very low aquatic concentrations were measured (concentration dependence). However, these values may serve as worst case values.

Conclusions:

In this study, water samples and samples from worms, crustaceans and bivalves were taken from the Dutch Rhine estuary and analysed for La, Ce and Nd. Bioaccumulation factors were reported to be 15000-50000 L/kg dw for bivalves, 8000-120000 L/kg dw for worms, and 10000-40000 L/kg dw for crustaceans. Ranges were reported in a lumped way for La, Ce, and Nd. These BAF values may be in the upper range of BAF values for REEs because they were observed at very low aquatic concentrations (concentration-dependency of metal uptake).

Reference 10

Endpoint:

bioaccumulation in sediment species: invertebrate

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Remarks:

Scientific review listing available data on several endpoints. Source publication not available. It is important to note that field studies provide snapshots in time of environmental concentrations of polluents and therefore cannot entirely guarantee steady state in the sampled organisms. For this reason, BAF values resulting from such studies have to be considered with caution.

Qualifier:

no guideline followed

Principles of method if other than guideline:

BAFs were determined in a field study for amphipods in salt and brackish water.

GLP compliance:

not specified

Radiolabelling:

not specified

Details on sampling:

no data

Vehicle:

no

Test organisms (species):

other: Corophium volutator (amphipoda)

Details on test organisms:

TEST ORGANISM
- Common name: mud shrimp
- Source: field collection

Route of exposure:

other: aqueous and sediment

Test type:

field study

Water / sediment media type:

natural sediment: marine

Hardness:

no data

Test temperature:

no data

pH:

8-8.5

Dissolved oxygen:

no data

TOC:

no data

Salinity:

30 g/L

Details on test conditions:

SEDIMENT
- harbour sediment from Nieuwe Maas, Rijnmond, The Netherlands

Nominal and measured concentrations:

Not reported by Sneller et al. (2000).

Details on estimation of bioconcentration:

Determination of BAF: content of Ce in biota per content of Ce in pore water (mg/kg dw per mg/L)

Type:

BAF

Value:

48 978

Basis:

whole body d.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: field data

Remarks:

Conc. in environment / dose: concentration in pore water: no data given

Conclusions:

In this study, field samples were taken from sediment and amphipods (Corophium volutator) from a harbour in the Netherlands. Based on Ce measured in pore water and amphipods, a BAF of 48978 L/kg dw could be calculated. Ce concentrations in pore water and supernatant water may have been very low. Note that a concentration dependency may exist for Ce resulting in higher BAF values with decreasing Ce concentrations in water.

Reference 11

Endpoint:

bioaccumulation in aquatic species: aquatic plant

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:

Reliable with restrictions (Klimisch 2) because most likely radioactivity in water was not measured in filtered samples.

Qualifier:

no guideline followed

Principles of method if other than guideline:

In this study, the uptake of radiolabeled Ce from water by Ulva lactuca was studied, as well as the influence of pCO2, pH and time on bioconcentration.

GLP compliance:

not specified

Radiolabelling:

yes

Details on sampling:

In the first and second experiment (constant pH or pCO2), at the end of the 15 min exposure time, Ulva disks were quickly removed, rinsed with non-spiked seawater, patted dry and placed into tared plastic petri dishes for weighing and counting.
Seawater samples were taken at the start of the experiment as well as after 15 min.
In the third experiment, in which time was varied, similar samples were taken after 1, 3, 5, 10, 15, 30, 60, 180, 360 min (and 1330 min in the longest sub-experiment).

Vehicle:

no

Details on preparation of test solutions, spiked fish food or sediment:

A stock solution of spiked seawater was prepared by adding 20-40 µCi of 144Ce to 600 mL of filtered seawater (total added metal ca. 5E-08 mol/kg solution). 1 h of equilibration was foreseen. When equilibration was attained, 100 mL of stock solution was added to a 250 mL thermostatic beaker.

Test organisms (species):

other: Ulva lactuca

Details on test organisms:

Ulva lactuca was collected along the southern shore of Tampa Bay within 48 h of each experiment.
12 h before the start of an experiment, tissue discs were cut out of the sampled specimens (diameter 14 mm).

Route of exposure:

aqueous

Test type:

static

Water / sediment media type:

natural water: marine

Total exposure / uptake duration:

15 - 1 330 min

Hardness:

not reported

Test temperature:

20°C

pH:

Experiments in which pH was varied: pH 6.28 up to 8.97
Other experiments: pH 7.46 to 8.0, depending on the experiment

Dissolved oxygen:

not reported
Experiments in which pCO2 was varied: pCO2 = 164 up to 1650 x 10^-6 atm
Other experiments: pCO2 = 329 or 1219 x 10^-6 atm, depending on the experiment

TOC:

not reported

Salinity:

36.4 ppt

Details on test conditions:

Three experiments were performed:
1. pH was held constant and REE uptake was monitored as a function of the solution partial pressure of CO2.
2. CO2 partial pressure was held constant and REE uptake was monitored as a function of pH.
3. pCO2 and pH were held constant while metal uptake was followed through time. An experiment of 360 min was performed at pCO2 of 329E-06 atm and pH 7.5, another experiment of 1330 min was performed at pCO2 of 329E-06 atm and pH 8.0, and a last experiment of 360 min was performed at pCO2 of 1219E-06 atm and pH 8.0.
Experiment 1 and 2 were performed over 15 min.
Seawater was collected near the surface, well offshore in the eastern Gulf of Mexico (27°N, 86°W). It was filtered through 0.5 µm polycarbonate filters (Nuclepore).
Three Ulva disks (patted dry) were added to each solution treatment (in 250 mL beakers with 100 mL of test solution).
Bubbling gas provided gentle agitation during the experiment.
Where pH or pCO2 needed to be constant, the necessary amounts of NaHCO3 were added.

Nominal and measured concentrations:

7 µg Ce/L (ca.)

Details on estimation of bioconcentration:

Partition coefficients were calculated by dividing the counts/s/g of Ulva by the counts/s/g of seawater and correcting the ratio by a geometry correction factor that compensates for the differences in counting efficiency attributable to purely physical (geometrical) differences between Ulva discs and liquid seawater samples. For Ce, this correction factor was 2.02 +/- 0.15 (determined empirically).

Type:

BCF

Value:

1.72 - 979.66 L/kg

Basis:

whole body w.w.

Calculation basis:

other: steady state was not reached in all experiments

Remarks on result:

other: range for all experiments

Remarks:

Conc. in environment / dose: ca. 7 µg Ce/L

Details on results:

There was a slight decrease of bioconcentration with increasing pCO2.
A drastic decrease of bioconcentration with increasing pH was observed.
In most experiments steady state was not reached and bioconcentration increased with increasing exposure time.

Conclusions:

In this study, bioconcentration of 144Ce by Ulva lactuca was studied with increasing pH, pCO2 levels, and time. Overall, BCF values ranged from 1.72 to 979.66 L/kg ww. A decrease of BCF values was observed with increasing pCO2 levels and - more drastically - increasing pH levels. Bioconcentration also increased with increasing exposure time (within the exposure duration range tested in this study). Overall, the affinity of Ulva lactuca for Ce uptake decreased with increasing carbonate levels in solution.

Reference 12

Endpoint:

bioaccumulation in aquatic species, other

Remarks:

aquatic plants and aquatic invertebrates

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:

Klimisch 2 score assigned because data was only presented in figures, which yields somewhat less accurate values. It is important to note that field studies provide snapshots in time of environmental concentrations of polluents and therefore cannot entirely guarantee steady state in the sampled organisms. For this reason, BCF/BAF values resulting from such studies have to be considered with caution.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Samples were taken from five locations in the Netherlands. Concentrations of cerium were measured in five different species of snails, two different species of bivalves, and in common duckweed. Further, sediment fractions (< 2mm and < 63 µm), surface water and sediment pore water were analysed for Ce.

GLP compliance:

not specified

Radiolabelling:

no

Details on sampling:

Sampling locations were all situated in the catchment of the Rhine and Meuse rivers:
- Veluwemeer
- Botlekpark, Rozenburg
- Kralingse Plas, Rotterdam
- Nieuwe Maas, Rotterdam
- Charlois, Rotterdam
Samples were taken in August and September 2000.
Surface water samples (n=3): filtered 0.45 m.
Pore water samples (n=3): extracted in situ using Rhizon soil moisture samplers.
Sediment samples (n=3): collected with a bottom sampler according to Ekman-Birge.
Common duckweed (Lemna minor) (n=2): collected with a small plastic sieve, unwanted material removed with plastic tweezers.
Molluscs (n=2-20): hand-collected, allowed to empty their guts in native water for 3-5 h, shells cleaned on outside with soft plastic brush.

Vehicle:

no

Test organisms (species):

other: different molluscs (snails and bivalves) and Lemna minor

Details on test organisms:

- Snails: Potamopyrgus antipodarum; Lymnaea stagnalis; Radix ovata.; Physella acuta; Planorbarius corneus; Planorbis planorbis
- Bivalves: Dreissena polymorpha and Corbicula fluminae
- Common duckweed, Lemna minor

Route of exposure:

aqueous

Test type:

field study

Water / sediment media type:

natural sediment: freshwater

Hardness:

no data

Test temperature:

Range of all sampling locations: 18 - 21 °C (surface and pore water)

pH:

Range of all sampling locations: 7.3 - 8.72 (surface water), 6.92 - 7.55 (pore water)

Dissolved oxygen:

no data

TOC:

no data

Salinity:

no data

Details on test conditions:

Sampling sites:
- Five locations in The Netherlands: four of them in the highly industrialised region around the city of Rotterdam (Botlekpark, Kralingse Plas, Nieuwe Maas (slightly brackish), Charlois)
- All sampling locations are situated in the catchment of the Rhine and Meuse rivers, and hence the sediments originate from the same source, a well-mixed riverine flood plain.
- Samples were taken in August and September 2000
- a large and open freshwater body (Veluwemeer) served as control.

Nominal and measured concentrations:

surface water: approx. 0.5 - 2 nmol Ce/L (measured)
pore water: approx. 0.2 - 1 nmol Ce/L (measured)

Details on estimation of bioconcentration:

The bioconcentration factor was estimated from the monitoring data for Ce in surface water and organisms and was expressed in L/kg dw.

Type:

BAF

Value:

ca. 950 - 40 000 L/kg

Basis:

whole body d.w.

Remarks:

soft tissue

Calculation basis:

other: assumed steady state

Remarks on result:

other: snails: L. stagnalis, R. ovata, P. Planorbis, P. acuta, P. antipodarum

Remarks:

Conc. in environment / dose: concentration in surface water: approx. 0.07-0.28 µg Ce/L

Type:

BAF

Value:

ca. 2 000 - 4 000 L/kg

Basis:

whole body d.w.

Remarks:

soft tissue

Calculation basis:

other: assumed steady state

Remarks on result:

other: bivalves (C. fluminae, D. polymorpha)

Remarks:

Conc. in environment / dose: concentration in surface water: approx. 0.07-0.28 µg Ce/L

Type:

BCF

Value:

ca. 2 000 - 3 000 L/kg

Basis:

whole body d.w.

Calculation basis:

other: assumed steady state

Remarks on result:

other: common duckweed, Lemna minor

Remarks:

Conc. in environment / dose: concentration in surface water: approx. 0.07-0.28 µg Ce/L

Generally, the concentrations in the organisms reflect exposure over a longer time period, while the analysis in the surface water only reflects one point in time.

There was no significant variation in sediment and surface or pore water cerium concentrations at the five locations (four of them being located near a highly industrialised region and one of them representing a control region). Therefore, the range of BAF/BCF values obtained for each group of organisms is reported in the result box, not distinguishing between the individual sampling sites.

The samples taken for this study may be considered representative for background concentrations in The Netherlands, based on the lack of any significant variation in sediment/surface/pore water concentrations, sampled at five locations with different characteristics. However, the biota (plants and molluscs) showed significant variation in cerium concentrations for the various locations, comprising about two orders of magnitude. This may be attributed to inter- and intra-specific biological variation, differences in cerium speciation and the involvement of different cerium sources for organisms, e.g. surface water, pore water and food for snails.

Conclusions:

In this study, samples of sediment, surface water, pore water, and biota were taken at five locations in the Rhine Meuse estuary and analysed for Ce. For snails, molluscs, and common duckweed, BAF/BCF values were obtained of 950-40000, 2000-4000 and 2000-3000 L/kg dw, respectively.

Reference 13

Endpoint:

bioaccumulation in aquatic species, other

Remarks:

fish, aquatic invertebrates, aquatic plants

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:

it is not entirely clear why for certain organisms no BCF/BAF values were reported, since data in figures indicate relevant bioconcentration/bioaccumulation. Mixed exposure.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Microcosm study for evaluation of distribution and bioavailability of rare earth elements. Duckweed (phytoplankton), Daphnia (crustaceans), shellfish (benthic species) and goldfish (fishes) were used as representative aquatic community.

GLP compliance:

not specified

Radiolabelling:

no

Details on sampling:

Water, sediment, duckweed, daphnids: sampled at 12, 24, 48, 96, 192, 288, 384 h.
Shellfish and goldfish: sampled at 48, 96, 192, 288, 384 h.
Water samples: 5 mL, filtered 0.45 µm.
Sediment samples: washed by deionised water, dried by air, 0.5 g digested with Na2O2 under 700°C and passed through cation-exchange columns.
Organism samples: 50 mg duckweeds, 30 daphnids, 1 shellfish, 1 goldfish digested (HNO3 and HClO4). Final solutions brought to 5 mL with 7% HCl.

Vehicle:

no

Details on preparation of test solutions, spiked fish food or sediment:

Water and sediment samples were collected from an eutrophic lake - Xuanwu Lake in Nanjing, China.
Water 0.45 µm filtered.
Sediment samples dried by air and weighed before adding to aquarium.
Sediment was placed at the bottom of the aquarium to about 2 cm thick (aquarium of 20x50x50 cm).
50 L lake water was added.
After 1 week equilibration (with organisms added too), a stock solution (mixture of five REEs with 1.00 mg/mL each) was spiked into the aquarium to 1 mg/L.

Test organisms (species):

other: duckweed, Daphnia, shellfish, goldfish

Details on test organisms:

1. Duckweed (Sperollela polyrrhiza), cultured in laboratory.
2. Crustaceans (Daphnia magna), parthenogenetic females maintained in laboratory and fed unicellular green algae (Chlorella pyrenoidosa, cultures in HB-4 aqueous medium by the method of Hua (1986).
3: Goldfish (Carassius auratus): 5 cm body length, fed commercial fish food.
4. Shellfish (Bellamya aeruginosa): reared in laboratory.
All organisms acclimated to laboratory conditions one week prior to the experiment.

Route of exposure:

aqueous

Test type:

static

Water / sediment media type:

natural sediment: freshwater

Total exposure / uptake duration:

16 d

Hardness:

not reported

Test temperature:

water temperature held at 22 +/- 1 °C

pH:

kept at ca. 6.5-6.8

Dissolved oxygen:

not reported (continuous aeration)

TOC:

not reported

Salinity:

not applicable

Details on test conditions:

TEST SYSTEM
- Test vessel: aquarium
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: aquarium 20x50x50 cm), 50 L lake water, 2 cm thick sediment layer
- Aeration: yes
- No. of organisms per vessel: 400 adult daphnids (placed in nylon cage 15x15x20 cm with 1x1 mm mesh to maintain adult daphnids while allowing larvae to swim through freely), 20 g duckweeds (ww), 30 shellfish, 15 goldfish
- No. of vessels per concentration (replicates): 1
- No. of vessels per control / vehicle control (replicates): 1

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Lake water (Xuanwu Lake, Nanjing, China)
- Holding medium different from test medium: yes
- Intervals of water quality measurement: physicochemical characteristics of sediment and water of Xuanwu Lake have been studied by Nanjing EPA (1996).

OTHER TEST CONDITIONS
- Adjustment of pH: pH kept at 6.5-6.8 because REEs will precipitate under alkaline conditions
- Photoperiod: 12L:12D
- Light intensity: not reported, fluorescent lamps used

Nominal and measured concentrations:

nominal: 1 mg Ce/L
measured: ca. 0.2 mg Ce/L

Reference substance (positive control):

no

Details on estimation of bioconcentration:

BCF/BAF values calculated dividing concentrations in test species (mg/kg ww), corrected for background concentrations observed in the control, by concentrations in test water (mg/L).

Type:

BAF

Value:

ca. 2.75 L/kg

Basis:

whole body w.w.

Calculation basis:

steady state

Remarks on result:

other: shellfish, not reported in Table but derived based on Figure for 16 d sampling point

Remarks:

Conc. in environment / dose: ca. 0.2 mg Ce/L

Type:

BCF

Value:

214.3 L/kg

Basis:

whole body w.w.

Calculation basis:

steady state

Remarks on result:

other: duckweed, reported in Table for 16 d sampling point

Remarks:

Conc. in environment / dose: ca. 0.2 mg Ce/L

Type:

BAF

Value:

ca. 400 L/kg

Basis:

whole body w.w.

Calculation basis:

steady state

Remarks on result:

other: Daphnia, not reported in Table but derived based on Figure for 16 d sampling point

Remarks:

Conc. in environment / dose: ca. 0.2 mg Ce/L

Type:

BAF

Value:

ca. 1.25 L/kg

Basis:

whole body w.w.

Calculation basis:

steady state

Remarks on result:

other: goldfish, not reported in Table but derived based on Figure for 16 d sampling point

Remarks:

Conc. in environment / dose: ca. 0.2 mg Ce/L

Details on results:

In fish and shellfish BAFs were rather low compared to Daphnia and duckweed, where BAF/BCF values were about 100-fold higher.
BAF = Bioaccumulation factor, combined exposure via food and water (i.e., because this is a microcosm study in which the organisms are not administered external feed, the animals in the microcosm study were exposed both via water and via food).
BCF = Bioconcentration factor, exposure via water only (in this case relevant for the plants present in the microcosm study).

Reported statistics:

Student's t test for comparison of treatments with control, p <= 0.05.

Conclusions:

In this microcosm study, goldfish, shellfish, Daphnia and duckweed were exposed for up to 16 days to a single concentration of Ce (added as a mixture of REEs). Ce analysis in samples taken after 16 days of exposure yielded BCF/BAF values of ca. 1.25, ca. 2.75, 214.3 and ca. 400 L/kg ww for goldfish, shellfish, duckweed and Daphnia, respectively.

Reference 14

Endpoint:

bioaccumulation in aquatic species: algae / cyanobacteria

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:

mixed exposure, and no analytical follow-up of Ce and La concentration in test medium (concentrations may have been lower).

Qualifier:

no guideline followed

Principles of method if other than guideline:

In a mixed exposure system (La3+ + Ce4+), Microcystis aeruginosa was exposed for up to 7 days and frequent samples were taken for analysis of accumulated La and Ce.

GLP compliance:

not specified

Radiolabelling:

no

Details on sampling:

Samples for analysis of La and Ce accumulated by the blue-green algae were taken after 24, 48, 72, 96, 120, 144 and 168 h of exposure.

Vehicle:

no

Test organisms (species):

Microcystis aeruginosa

Details on test organisms:

Microcystis aeruginosa Kütz, freshwater blue green algae, obtained from Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China.
Algae grown in HGZ medium.
Initial cell density during test not clearly reported.

Route of exposure:

aqueous

Test type:

static

Water / sediment media type:

natural water: freshwater

Total exposure / uptake duration:

168 h

Hardness:

not reported

Test temperature:

28 +/- 1°C

pH:

adjusted to pH 8

Dissolved oxygen:

not reported

TOC:

not reported

Salinity:

not applicable

Details on test conditions:

TEST SYSTEM
- Test vessel: not clearly reported
- Material, size, headspace, fill volume: not clearly reported
- Aeration: no
- No. of organisms per vessel: initial cell density not clearly reported
- No. of vessels per concentration (replicates): 2
- No. of vessels per control / vehicle control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: HGZ medium
- Holding medium different from test medium: no

OTHER TEST CONDITIONS
- Adjustment of pH: adjustment to pH 8
- Photoperiod: 12L:12D
- Light intensity: 2000 lux
- Vessels shaken manually 4 times a day

Absorbance was measured periodically at 650 nm using a spectrophotometer.

Nominal and measured concentrations:

Nominal (La3+ + Ce4+):
Control (0 + 0 mg/L), 0.5 + 0.05 mg/L, 0.5 + 0.1 mg/L, 0.5 + 0.2 mg/L, 1 + 0.05 mg/L, 1 + 0.1 mg/L, 1 + 0.2 mg/L, 2 + 0.05 mg/L, 2 + 0.1 mg/L, 2 + 0.2 mg/L.

Reference substance (positive control):

no

Details on estimation of bioconcentration:

BCF values were calculated dividing observed accumulation at equilibrium (mg Ce/kg dw) by nominal concentrations in the test medium (mg Ce/L).

Type:

BCF

Value:

72 000 - 86 000 L/kg

Basis:

whole body d.w.

Calculation basis:

steady state

Remarks on result:

other: Range for treatments with 0.05 mg Ce/L and either 0.5, 1 or 2 mg La/L.

Remarks:

Conc. in environment / dose: 0.05 mg Ce/L (nominal)

Details on kinetic parameters:

Second order kinetics absorption model (Ho et al., 1996) provides realistic description of sorption process.
Model: t/qt = (1/2 * k2 * qe^2) + t/qe
With
k2 = second order rate constant for sorption (g/mg/h)
qe = amount of Ce absorbed at equilibrium (mg/g)
qt = amount of Ce absorbed at tim (mg/g)
k2 was reported to be 0.56 to 0.86 g/mg/h.

Details on results:

Ce4+ can directly penetrate through cell membrane into algal cells, but can also move into algal cells through anionic pathways by forming complex anions e.g. with Cl- and OH- in culture solution. Ca2+ transport systems may be involved.

Conclusions:

In this study, Microcystis aeruginosa was exposed for up to 7 days to combined concentrations of La3+ and Ce4+. At a nominal concentration of 0.05 mg Ce/L, BCF values of 72000 to 86000 L/kg dw were obtained. Because at the pH of the study (8), Ce may have been precipitated to a certain extent, and Ce was not analytically determined in the test medium, these factors may actually have been even higher.

Description of key information

The endpoint was covered using a weight of evidence approach including 11 publications that were assigned a K2 score (reliable with restrictions) (one publication was assigned a K4 score - not assignable - because the original source was not available). Overall, bioconcentration/bioaccumulation was only observed to be high in organisms from lower trophic levels in the foodchain. Cerium does not seem to accumulate further in the aquatic foodchain, as was clear from the results of four studies with fish, including one study reporting BMF factors for organisms in three different aquatic foodchains. A key BCF/BAF value of 16 L/kg ww was calculated for fish as a worst case key value for use in case exposure calculations are needed for secondary poisoning (aquatic foodchain) or man via the environment.

Key value for chemical safety assessment

BCF (aquatic species):

16 L/kg ww

Additional information

Overall, 11 publications (of which one review) were identified as useful in a weight of evidence approach for aquatic bioaccumulation. Data are available for fish, aquatic invertebrates, aquatic plants, and a blue-green alga. The available data were both from field studies and laboratory experiments and for both freshwater and marine organisms. In all studies, cerium concentration in (parts of) the exposed organisms was analytically determined, as well as cerium concentration in the water column (the latter was not the case in all studies). In the laboratory studies, soluble cerium compounds such as cerium trichloride and cerium trinitrate were used or sometimes also mixtures of salts of different rare earth elements were used (i.e., mixed exposure).

For aquatic plants (algae as well as higher plants) and blue-green algae, six studies were identified as containing useful information on bioconcentration of cerium. Weltje et al. (2002) reported BCF values between 2000 and 3000 L/kg dw for Lemna minor sampled along the Rhine-Meuse estuary (corresponding to 400 and 600 L/kg ww, assuming 20% dw, which is a very conservative value for aquatic plants). In a microcosm study in which goldfish, shellfish, Daphnia and duckweed were exposed for up to 16 days to cerium (Yang et al., 1999), a BCF value of 214.3 L/kg ww (assuming 20% dw corresponding to 1071.5 L/kg dw) was calculated for duckweed for the 16-d sampling point. In the study of Kumblad and Bradshaw (2008), BCF values were reported ranging from 20 to 2800 L/kg ww (corresponding to a range of 966 to 48611 L/kg dw, using ww-dw conversion factors reported in the publication) for microalgae and macroflora sampled from locations in the Forsmark area. Zhou et al. (2004) performed a laboratory study with the blue-green alga Microcystis aeruginosa and obtained BCF values of 72000 to 86000 L/kg dw (assuming 20% dw corresponding to 14400-17200 L/kg ww). From the study of Drndarski and Golobocanin (1995) a BCF value of ca. 1000 L/kg dw was obtained for periphyton sampled in the Sava River (affected by the Chernobyl accident) (assuming 20% dw corresponding to 200 L/kg ww). Finally, Stanley and Byrne (1990) reported BCF values of 1.72 to 979.66 L/kg ww (assuming 20% dw corresponding to a range of 8.6 to 4898 L/kg dw) for Ulva lactuca obtained in a series of experiments in which either time, pCO2 or pH were varied. The overall range of BCF values obtained in these studies was 8.6 to 86000 L/kg dw (corresponding to a range of 1.72-17200 L/kg ww), indicating that cerium is bioconcentrated in aquatic plants and blue-green algae.

Seven studies contained useful information on bioconcentration/bioaccumulation of cerium in aquatic invertebrates. Carpenter and Grant (1967) reported BAF values of 60 to 1000 L/kg ww (corresponding to 300 to 5000 L/kg dw when assuming 20% dw) for Crassostrea virginica and Mya arenaria sampled from two coastal areas (Chesapeake Bay and Chincoteague Bay). Moermond et al. (2001) reported BAF/BCF values for Corophium volutator taken from the field (Dutch locations) as well as for a laboratory study with the species. The values ranged from 3390 to 17500 L/kg dw (corresponding to 678 to 3500 L/kg ww when assuming 20% dw). Sneller et al. (2000) discussed the results of Tijink and Yland (1998) and Stronkhorst and Yland (1998). The first study calculated BAF values for worms, crustaceans and bivalves taken from the Dutch Rhine estuary. The latter study calculated BAF values for amphipods (Corophium volutator) taken from a harbour in the Netherlands. The values from these studies ranged from 8000 to 120000 L/kg dw (corresponding to 1600 to 24000 L/kg ww when assuming 20% dw). For snails and molluscs sampled along the Rhine-Meuse estuary, Weltje et al. (2002) reported BAF values of 950 to 40000 and 2000 to 4000 L/kg dw, respectively (corresponding to an overall range of 190 to 8000 L/kg ww when assuming 20% dw). In the microcosm study of Yang et al. (1999) the BAF values after 16 days of exposure were 2.75 and 400 L/kg ww for shellfish and Daphnia, respectively (assuming 20% dw corresponding to 13.75 and 2000 L/kg dw). And finally, Kumblad and Bradshaw (2008) reported BAF values for aquatic invertebrates sampled from locations in the Forsmark area ranging from 640 to 11000 L/kg ww (corresponding to a range of 3837 to 349398 L/kg dw, using ww-dw conversion factors reported in the publication). Overall, the BCF/BAF values ranged from 13.75 to 349398 L/kg dw (corresponding to a range of 2.75 to 24000 L/kg ww), indicating that cerium is also bioconcentrated in aquatic invertebrates.

For bioconcentration/bioaccumulation in fish, four studies were identified. The laboratory study of Sun et al. (1996) reported BCF values for muscle, skeleton, gills, and internal organs of carp (Cyprinus carpio) after 43 days of exposure to a mixture of rare earth elements, among which cerium. Maximum BCF values for muscle tissue, skeleton, gills, and internal organs were 1.46, 5.94, 14.8 and 804 L/kg ww, respectively. The BCF values for internal organs were highest but are not considered as a good indication of the bioconcentration potential of cerium, since the alimentary tract reflects the normal transit of the substance. The second study (Yang et al., 1999) was a microcosm study in which goldfish, shellfish, Daphnia and duckweed were exposed for up to 16 days to cerium. The BAF value for goldfish (Carassius auratus) appeared to be around 1.25 L/kg ww, based on whole body analysis. This is in agreement with the low values for muscle and skeleton observed in the study from Sun et al. (1996). The third study (Carpenter and Grant, 1967) reported a BAF value of < 20 L/kg ww for edible portions of striped bass sampled in the field, which also confirms that bioconcentration/bioaccumulation of cerium in fish is rather low. Finally, the study of Kumblad and Bradshaw (2008) reported BAF values between 1.8 and 4.6 L/kg ww when internal organs were removed from fish sampled in the Forsmark area. BAF values varied between 110 and 2000 L/kg ww however when whole fish were analysed. This is in agreement with the results from the study of Sun et al. (1996), which obtained higher bioconcentration/bioaccumulation in internal organs.

Overall, bioconcentration/bioaccumulation in fish seemed to be substantially lower than in organisms at a lower level in the food chain. The fact that goldfish in a microcosm study (in which they could feed on other organisms present in the microcosm) showed a low bioaccumulation factor (BAF = 1.25 L/kg ww) indicates that the high bioconcentration/bioaccumulation is leveled out when ascending along the foodchain. This is confirmed by the results on biomagnification in three aquatic foodchains reported by Kumblad and Bradshaw (2008). Biomagnification factors (BMFs) were generally 0 or 1 for all organisms, except one value for zooplankton which was 374 kg/kg (dw based). For fish (whether planktivore, feeding on benthos, or carnivore), BMFs were all <= 1 kg/kg (dw based), confirming that biomagnification is not an issue for cerium.

Clearly, cerium has a limited potential to bioaccumulate through the foodchain and it definitely does not biomagnify. Similar differences in bioconcentration/bioaccumulation between different trophic levels have been observed for other metals. In case exposure assessments need to be performed, a value is needed that can be used for calculating exposure levels in prey via the generic scenario for secondary poisoning starting in the aquatic foodchain, as well as for calculating exposure levels for exposure of man via the environment. An average (geometric mean) BCF/BAF of 16 L/kg ww for fish was therefore calculated based on the results of the four available studies. Before calculating the overall mean, a study-specific mean (geometric mean) was calculated for each study. For Sun et al. (1996), all data were included, also those for internal organs. For Kumblad and Bradshaw (2008), only the results for whole fish were included (i.e., not those for samples from which the internal organs were removed). Therefore, the obtained value can be considered as a worst case value.

Finally, on the relatively high values observed for aquatic plants, blue-green algae, and aquatic invertebrates, it should be noticed that many of the studies investigated bioconcentration/bioaccumulation at a very low environmental concentration of cerium (e.g., 1 µg Ce/L or lower). What is often observed for metals is that bioconcentration/bioaccumulation is concentration dependent, showing increasing BCF/BAF values with decreasing (almost background) environmental concentrations. This may also have shifted the upper boundaries of the ranges for these trophic levels up. Overall, the results for fish clearly indicate that bioconcentration/bioaccumulation is typically high only for lower trophic levels and cerium does not further accumulate through the foodchain. Metals are typically well regulated by living organisms, especially when they are essential for their vital functions. For cerium, there is evidence available that it is either an essential element that is needed at extremely low concentrations or it can stimulate certain vital functions. The concentration dependency of the BCF/BAF values in organisms from lower trophic levels may be explained to a certain extent by this.