Sodium dichromate

Sediment toxicity

Link to relevant study record(s)

Reference

Endpoint:

sediment toxicity: long-term

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Although not all the experimental details are given in the paper, it is clear that the studies were conducted in accordance with the referenced guideline. However, the test did not include a geometric series of test concentrations but rather three different sediments with different concentration of Cr were tested. Decreasing pore water concentrations of chromium over the test duration indicate that the equilibration time of sediment prior to the test was too short, thus presumably leading to an overestimation of Cr toxicity in sediments.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

ASTM E1706 (Test Method for Measuring the Toxicity of Sediment-Associated Contaminants with Freshwater Invertebrates)

Version / remarks:

04. Remark: ASTM E1706-00

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EPA/600/R-99/064 (Method for Measuring the Toxicity and Bioaccumulation of Sediment-Associated Contaminants with Freshwater Invertebrates)

Deviations:

no

GLP compliance:

no

Analytical monitoring:

yes

Details on sampling:

Overlying water (filtered): samples for total Cr and Cr(VI) were taken at days 0, 14, and 28; (day 42 for aqueous exposures)
Spiked sediment: total Cr, SEM metals in controls (day 0); SEM-Cr and AVS (days 0 and 28)
Pore water (filtered): Total Cr and Cr(VI) (days 0, 28); SEM metals, in high treatment (day 0)

Vehicle:

no

Details on sediment and application:

PREPARATION OF SPIKED SEDIMENT
- Details of spiking: Spike solutions of K2Cr2O7 were prepared in deionised water and 300 mL was added to 3 L of wet sediment
- Equilibration time: 1 week
- Equilibration conditions: Initially stirred thoroughly and then stored at 4C with periodic mixing
- Controls: Control sediment were prepared by mixing sediments with 300 mL of deionised water

Test organisms (species):

Hyalella azteca

Details on test organisms:

TEST ORGANISM
- Age of animals at beginning of exposure: 7 d
- Feeding during test: yes
- Food type: Yeast-cereal-trout chow (YCT) suspension
- Amount: 1.8 mg/beaker
- Frequency: daily

Study type:

laboratory study

Test type:

semi-static

Water media type:

freshwater

Type of sediment:

natural sediment

Limit test:

yes

Duration:

42 d

Exposure phase:

other: total test duration

Duration:

28 d

Exposure phase:

total exposure duration

Duration:

14 d

Exposure phase:

reproduction phase

Remarks:

in clean test water

Post exposure observation period:

Surviving animals were removed from sediment after 28 days and transferred to clean water for 14 days to facilitate reproduction measurements.

Hardness:

Sediment and pore water:
0.6 to 4.8 mM (control sediment)
0.3 to 2.8 mM (Cr(VI) spiked sediment)
Overlying water:
0.125 to 0.145 mM (control)
0.119 to 0.149 mM (Cr(VI) spiked sediment)

Test temperature:

23 °C

pH:

Sediment and pore water:
pH 6.03 to 7.46 (control sediment)
pH 5.85 to 8.95 (Cr(VI) spiked sediment)
Overlying water:
pH 7.94-8.12 (control)
pH 7.57-8.22 (Cr(VI) spiked sediment)

Dissolved oxygen:

Not stated.

Salinity:

Not relevant.

Ammonia:

Sediment and pore water:
1.6 to 8.6 mg/L (control sediment)
1.0 to 7.9 mg/L (Cr(VI) spiked sediment)
Overlying water:
0.23 to 0.35 mg/L (control)
0.23 to 0.60 mg/L (Cr(VI) spiked sediment)

Conductivity:

Overlying water:
323-334 µS/cm (control)
320-357 µS/cm (Cr(VI) spiked sediment)

Nominal and measured concentrations:

See Table 2 in 'Any other information on results incl. tables'.

Details on test conditions:

TEST SYSTEM
- Test container (material, size): 300 mL test beakers
- Sediment volume: 100 mL of test sediment
- Overlying water volume: 175 mL overlying water
- Three different sediments used for testing

EXPOSURE REGIME
- No. of organisms per container (treatment): 10
- No. of replicates: 16 replicates (4 replicates for 10-d survival , 4 to 8 replicates for 28-d survival and growth, 4 replicates for 28-d chemistry, 4 replicates for 42-d survival, growth, and reproduction)
- Feeding regime: daily
- Type and preparation of food: Yeast-cereal-trout chow (YCT) suspension
- Amount of food: 1.8 mg/beaker/day

RENEWAL OF OVERLYING WATER
- Details on volume additions: Replacement rate of 2 volumes/day

OVERLYING WATER CHARACTERISTCS
- Type of water (e.g. deionized, ground water, sea water, Elendt medium acc. to OECD 219): Well water diluted 1:1 with deionized water
- Alkalinity: 130 mg/L
- Salinity: Not stated
- Conductivity: 330 uS/cm
- Hardness: 140 mg/L

SOURCE OF NATURAL SEDIMENT
- Location and description of sampling site: Florissant, West Bearskin Lake, Columbia (USA)
- Contamination history of site: Not stated

HANDLING OF NATURAL SEDIMENT
- Time of collection: Not stated
- Core depth: Not stated
- Water depth: Not stated
- Storage conditions: Not stated
- Storage duration (prior to test): Not stated

CHARACTERIZATION OF SEDIMENT: See Table 1

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Survival (at 10, 28, 35, 42 days), growth (carapace length) (day 28) and reproduction (young per female) (at 35, 42 d)

Reference substance (positive control):

no

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

72.8 mg/kg sediment dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element (total fraction)

Remarks:

Cr

Basis for effect:

mortality

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

171.6 mg/kg sediment dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element (total fraction)

Remarks:

Cr

Basis for effect:

mortality

Duration:

42 d

Dose descriptor:

NOEC

Effect conc.:

2 704 mg/kg sediment dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element (total fraction)

Remarks:

Cr

Basis for effect:

reproduction

Remarks on result:

other: WB sediment

Duration:

42 d

Dose descriptor:

NOEC

Effect conc.:

2 548 mg/kg sediment dw

Nominal / measured:

meas. (not specified)

Conc. based on:

element (total fraction)

Remarks:

Cr

Basis for effect:

reproduction

Remarks on result:

other: CW sediment

Reported statistics and error estimates:

Standard error reported in Table 2 where n=4, except n=8 for 28 d survival.
ANOVA and Dunnett's test on rank-transformed data.

Table 2 - Characteristics of Sediments from a Toxicity test with Cr(VI) spiked sediments

				AVS (µmol/g)
Treatment	total Cr (µmol/g)	total Cr (mg/kg)	TOC (%)	day 0	day 28
FL-control	0.69	35.9	0.82	<0.01	<0.01
FL-Cr6	3.3	171.6	0.87	<0.01	<0.01
WB-control	1.4	72.8	9.0	33	28
WB 1x	52	2703.8	8.8	30	12
WB 3x	77	4003.7	8.9	21	13
WB 10x	220	11439.1	8.5	0.9	2.6
CW-control	1.2	62.4	2.2	55	51
CW 1x	31	1611.9	2.2	45	41
CW 1.5x	49	2547.8	2.0	30	35
CW 3x	94	4887.6	1.8	4.9	11

Table 3 - Characteristics of Porewater from a Toxicity test with Cr(VI) spiked sediments

	filterable Cr (µg/L)
Treatment	day 0	day 28
FL-control	4	43
FL-Cr6	276000	39400
WB-control	2	10
WB 1x	67	235
WB 3x	1070	132
WB 10x	695000	19500
CW-control	4	3
CW 1x	74	358
CW 1.5x	178	485
CW 3x	133000	4450

Table 4 - Results of a toxicity test with the amphipod Hyalella azteca, exposed to Cr(VI) spiked sediments

Treatment	total Cr (mg/kg)	survival (%) day 28	length (mm) day 28	reproduction (young/female)
FL-control	35.9	96 (3)	4.5 (0.1)	8.7 (1)
FL-Cr6	171.6	0*	nd	nd
WB-control	72.8	96 (2)	4.5 (0.1)	8.7 (1)
WB 1x	2703.8	95 (3)	4.6 (0.1)	8.7 (2)
WB 3x	4003.7	91 (4)	4.7 (0.1)	6.6 (1)
WB 10x	11439.1	0*	nd	nd
CW-control	62.4	95 (3)	4.5 (0.1)	6.3 (1)
CW 1x	1611.9	95 (2)	4.7 (0.1)	6.1 (1)
CW 1.5x	2547.8	91 (4)	4.8 (0.1)	8.2 (4)
CW 3x	4887.6	79 (7)	4.3 (0.2)	3.8 (8)

Means with standard error (n ) 8 for survival, n ) 4 for length and reproduction).

Asterisk indicates significant decrease in Cr(VI) treatment, relative to appropriate

control (p e 0.05; ANOVA and Dunnett’s test with rank-transformed data). nd, no data.

Validity criteria fulfilled:

yes

Remarks:

Control survival (28 d) > 80%; control length (28 d) > 3.2 mm; control reproduction (28-42 d) > 2 young/female

Conclusions:

Amphipod (Hyalella azteca) survival was significantly affected in two treatments, in the FL sediment at 171.6 mg Cr/kg dw (LOEC) and in the WB sediment at 11439.1 mg Cr/kg. A NOEC of 72.8 mg Cr/kg dw was thus conservatively derived for the highest concentration below the LOEC, although no effects on survival were observed at significantly higher concentration in different sediments (WB, CW). For surviving amphipods, no significant effects on lentgh and reproduction were observed. Results show a strong dependence of Cr toxicity on sediment characteristics, in particular a correlation between toxicity and AVS in the sediment was shown. For the Florissant sediment, which showed toxicity at 171 mg/kg dw, the AVS was below 0.01 µmol/g, while VAS ranged from 2.6-28 µmol/g and 11-51 µmol/g in the West Bearskin and Columbia sediment, respectively. Furthermore, a significant decrease of pore water Cr concentrations from day 0 to day 28 indicates that sediments were not sufficiently equilibrated after spiking with Cr, thus potentially overestimating bioavailability and consequently toxicity of chromium to Hyalella azteca. However, the derived value for amphipod survival is considered as worst case for the chemical safety assessment.

Description of key information

In one reliable study, Hyallela azteca was exposed for 28 days to three different freshwater sediments spiked with potassium dichromate. Amphipod survival was significantly affected in two treatments, in the Florissant sediment at 171.6 mg Cr/kg dw (LOEC) and in the West Bearskin sediment at 11439.1 mg Cr/kg. A NOEC of 72.8 mg Cr/kg dw was thus conservatively derived for the Florissant sediment although effects on survival were not observed at higher concentrations in the two other sediments (West Bearskin, Columbia). For surviving amphipods, significant effects on length and reproduction could not be observed. Results indicate a strong dependency of Cr toxicity on sediment characteristics, in particular a correlation between toxicity and acide volatile sulfide (AVS) in the sediment was shown. For the Florissant sediment, in which toxicity was observed at 171.6 mg/kg dw, the AVS was below 0.01 µmol/g, whereas AVS ranged from 2.6-28 µmol/g and 11-51 µmol/g in the West Bearskin and Columbia sediment, respectively. Chromium (VI) is thermodynamically not favoured in anoxic sediments, but AVS are formed only in anoxic sediments. Therefore, sediments with measurable amounts of AVS should not contain chromium (VI). Thus, chromium (VI) may get reduced to chromium (III) and bound by AVS in the two other sediments. Furthermore, the large decrease of Cr concentrations of the pore water from day 0 to day 28 indicates that sediments may not have been sufficiently equilibrated after being spiked with chromium (VI). Thus, bioavailability and consequently toxicity of potassium dichromate to the sediment organism Hyalella azteca may be overestimated. However, the derived NOEC for amphipod survival is considered as worst case for the chemical safety assessment.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater sediment:

72.8 mg/kg sediment dw