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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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bioaccumulation in aquatic species, other
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
2 (reliable with restrictions)

Data source

Reference Type:
Bio-accumulation of environmental residues or rare earth elements in aquatic flora Eichhornia crassipes (Mart.) Solms in Guangdong Province of China
H. Chua
Bibliographic source:
The Science of the Total Environment 214 (1998) 79 - 85

Materials and methods

Test guideline
no guideline followed
Principles of method if other than guideline:
Samples of water hyacinth (Eichhornia crassipes) were harvested from inland water courses in the Guangdong Province of Southern China. The exposure to water contamination as well as atmospheric exposure was simulated.
For the simulation of substrate water contamination by rare earth elements (Ce, La, Pr, Nd, Sm and Y) solutions of these rare eath nitrates were prepared (100, 300, 600, 900, 1200 and 1500 ppm) and added in a 40ml aliquot to the 10l culture solution of each plant sample. After 21 days the roots, stems and leaves extracts were analyzed by inductively coupled plasma-atomic emission spectroscope and expressed as mg/g dry weight.
For the simulation of atmospheric exposure to rare earth elements the water hyacinth leaves were smeared with 300 ppm solution of the radioactive isotope 141Ce(NO3)3 for four times. After 1, 2, 4, 8, 12 and 16 days the radiation accumulated in the roots, stems and leaves ware measured using an alpha-beta-gamma counter.
GLP compliance:
not specified

Test material

Constituent 1
Reference substance name:
Cerium trinitrate
EC Number:
EC Name:
Cerium trinitrate
Cas Number:
cerium(3+) trinitrate

Sampling and analysis

Details on sampling:
Previous to the ICP-AES measurement, extracts of water hyacinth in culture solution from the roots, stems and leaves were prepared by boiling these parts in 4N HCl solution to extract the bio-accumulated rare earth elements.

Previous to the alpha-beta-gamma counter measurement the atmospheric exposed roots, stems and leaves were separately oven dried, machine ground and weighted.

Test solutions

Details on preparation of test solutions, spiked fish food or sediment:
Simulation of substrate water contamination:
Solutions containing nitrates of the rare earth elements were prepared at 100, 300, 600, 900, 1200 and 1500 ppm. A 40 ml aliquot of each solution of microelement fertilizer was added into the 10l culture solution of each plant sample. Deionised water was added to one plant to act as a control.

Simulation of atmospheric exposure to rare earth elements:
A 0.0215 mCi of 300 ppm 141Ce(NO3)3 solution (specific radioactivity of 1.25 mCi/ml) was evenly smeared on the 12 leaves of the plant surface. This procedure was repeated four times.

Test organisms

Test organisms (species):
other: Eichhornia crassipes (water hyacinth)
Details on test organisms:
Eichhornia crassipes (water hyacinth) harvested from inland water courses in the Guangdong Province of Southern China.

Study design

Route of exposure:
Test type:
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
> 1 - < 21 d

Test conditions

Not reported
Test temperature:
Not reported
Not reported
Dissolved oxygen:
Not reported
Not reported
Not reported
Nominal and measured concentrations:
Nominal exposure concentrations:
Simulation of substrate water contamination: Solutions of the rare earth nitrates at 100, 300, 600, 900, 1200 and 1500 ppm.
Simulation of atmospheric exposure to rare earth elements: A 0.0215 mCi of 300 ppm 141Ce(NO3)3 solution (specific radioactivity of 1.25 mCi/ml).
Reference substance (positive control):

Results and discussion

Bioaccumulation factor
> 2.9 - < 6.4
other: measured in the roots, stems and leafs
Time of plateau:
21 d
Calculation basis:
steady state
Remarks on result:
other: This concentration in the environment corresponds to the official common dosage of rare earths in agricultural plantations in China.
Remarks: environment / dose:0.4 mg/L (ppm)
not specified

Any other information on results incl. tables

The uptake and distribution of rare earth elements via water hyacinth root system is summarised in following table:

Accumulation of REEs in water hyacinth:

 Concentration of nitrates of REEs in fertilizer solution (ppm)  Concentration of nitrates of REEs in culture solution (ppm)  Bio accumulated REEs (ppm) Root Stem Leaf  Bioconcentration factor (BCF) Root Stem Leaf
100  0,4 3,51 4,19 5,57  8,8 10,3 1 3,9
 300  1,2 3,48 5,42 7,65  2,9 4,5 6,4
 600  2,4 4,97 7,30 10,50  2,1 3,0 4,4
 900  3,6 5,62 9,65 12,44 1,6 2,7  3,5
 1200  4,8 6,65 12,19  14,12  1,4 2,5 2,9
 1500  6,0 7,56 13,79 16,27  1,3 2,3 2,7

REE concentrations in the culture solutions were calculated based on the amount of REEs applied in 10l of culture solution.

The bio-accumulated values are averages of three samples.

The correlation between concentrations of REE residues in the various parts of the plant sample and that in the substrate water appeared relatively linear:

For the roots: Y = 1.94 + 0.03X, r= 0.999

For the stems: Y = 2.39 + 0.01X, r=0.999

For the leaves: X = 4.00 + 0.01X, r=0.992

being Y the residual concentrations n the various parts of the plant and X the rare earth concentrations in the substrate water.

These results show that water hyacinth could bio-accumulate rare earths to concentration ratios (BCF) higher than it has been reported in other agricultural crops.

The absorption and distribution of 141Ce tracer in water hyacinth were also studied. The bio-accumulation of cerium via leaves and distribution in different parts are summarized in the following table:

Parts Day 1  Day 2  Day 4  Day 8  Day 12  Day 16 
 Roots  Accumulation a (cpm); Percentage b (%)  1089; 12.7  13411; 4.2  2087; 12.8  2270; 10.4  2069; 13.2  1999; 13.5
 Stems  Accumulation (cpm);Percentage (%)  3515; 41,1 3987; 42.1   5590; 34.3  7715; 35.4  5211; 33.3  4989; 33.7
 Leaves  Accumulation (cpm);Percentage (%)  3945; 46.1  4138; 43.7  8611; 52.9  11821; 54.2  8348; 53.4  7816; 52.8
 Entire plant  Accumulation (cpm);Percentage c (%)  8549; 0.87  9466; 0.96  16288; 1.65  21806; 2.21  15628; 1.59  14804; 1.50

a Figures are averages of four plant samples.

bCe in each plant as a percentage of that in the entire plant.

c Percentages= (bio-absorption of Ce in entire plant / Ce applied on leaf surface).x100. Quantity of Ce applied was taken as

985x103 cpm / plant.

Absorption of Ce in the leaves reached a highest level of 11821 cpm, accounting for 54.2% of that of the entire plant.

Applicant's summary and conclusion

Validity criteria fulfilled:
Rare earth elements could enter into water hyacinth via the root system in substrate water that was contaminated by rare earth elements and via the leaves that were exposed to atmospheric contaminants. In either case, the absorbed rare earth elements could be distributed to and bio-accumulate in various parts of the plant.
Therefore, high rare earth element concentrations in the substrate water in which water hyacinth grew could possible lead to harmful effects if this aquatic flora is used as animal feed-stock and hence enters into the human food chain.