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Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Meets generally accepted scientific standards, well documented and acceptable for assessment. Justification for read-across: No data on the behavior of titanium carbide in the environment are available. Concentration data for titanium metal are appropriate for read-across for this endpoint as the soluble species released are expected to be similar for each of the compounds, and are thus expected to behave similarly in the environment. For more details refer to the attached description of the read across approach.
Reason / purpose for cross-reference:
read-across source
Qualifier:
no guideline followed
Principles of method if other than guideline:
The authors examined the partitioning behaviour of Ti and other trace metals between surface water and sediments and their environmental fate within the sediments. Water and sediment samples for the experiment were taken from 20 randomly chosen sites of the Blesbokspruit, a riparian wetland near Johannesburg, South Africa, which is affected by mining activities.

Concentrations of Ti were measured in the sediment samples as well as in the water phase. The partition coefficient Kd is calculated as follows (equilibrium is assumed):

Kd = Cs/Cw, with:
Cs = Ti concentration in the solid phase;
Cw = Ti concentration in the water phase.
GLP compliance:
not specified
Type of method:
other: monitoring data
Media:
sediment
Radiolabelling:
not specified
Analytical monitoring:
yes
Details on sampling:
- Water and sediment samples were taken from 20 randomly chosen sites within the Blesbokspruit wetland
- 2 water samples per site were collected and filtered (0.45 µm); one sample was acidified (3M HNO3) to pH < 2 to prevent precepitation of trace metals
- Water sample storage before analysis: in sealed plastic bottles pre-rinsed with HNO3 and deionized water at 4°C
- Sediment samples were taken form the sediment-water interface by means of completely inserting inverted 50 ml polypropylene centrifuge vials into the sediment; vials were digged out and closed without headspace
- Sediment sample storage before analysis: on ice in anaerobic jars (anoxic conditions maintained by BBL gas pack
Details on matrix:
COLLECTION AND STORAGE
- Geographic location: Blesbokspruit wetland (near Johannesburg, South Africa)
- Collection procedures:
* 2 water samples per site were collected and filtered (0.45 µm); one sample was acidified (3M HNO3) to pH < 2 to prevent precepitation of trace metals
* Sediment samples were taken form the sediment-water interface by means of completely inserting inverted 50 ml polypropylene centrifuge vials into the sediment; vials were digged out and closed without headspace
- Storage conditions:
* Water samples: in sealed plastic bottles pre-rinsed with HNO3 and deionized water at 4°C
* Sediment samples: on ice in anaerobic jars (anoxic conditions maintained by BBL gas pack

SEDIMENT PROPERTIES
- predominantly quartzose sand and silt with low amounts of gravel and clay
- % gravel: 0-44 (mean: 5.65)
- % sand: 11-85 (mean: 40)
- % silt: 8-73 (mean: 39.9)
- % clay: 4-43 (mean: 14.6)
- Organic carbon (%): 0.5-9 (2.28)
Details on test conditions:
Samples were diluted 1000 times with an internal standard.
To asses any external contamination while sampling, a trip blank was analyzed.
Key result
Phase system:
solids-water in sediment
Type:
log Kp
Value:
4.61 L/kg
Remarks on result:
other: mean log Kp value for 20 locations, range: 3.79-5.13
Transformation products:
no
Details on results (Batch equilibrium method):
See "Any other infromation on results incl. tables".
Statistics:
The partition coefficient Kd is calculated as follwos (equilibrium is assumed):
Kd = Cs/Cw,
with Cs = Ti concentration in the solid phase; Cw = Ti concentration in the water phase

1. Surface water samples

- pH: neutral to alkaline (pH 7-9.2) due to dolomitic bedrock

- Dissolved oxygen: 2.5–10.8 mg/L

- Electric conductivity: 521-2400 µS/cm (differences attributed to location of sampling point above or below discharge point of the Grootvlei mine effluent)

- Dominant anions: chloride (28-161 mg/L) and sulphate (73-702 mg/L)

- Dominant cations: Na+ (69-855 mg/L) and Ca+ (21 -195 mg/L)

- Charge balance was for all samples in the range of 0.1 -9.8 % (thus below the acceptable value of 10 %) ecept for one site where major cations were underestimated (imbalance: 29 %)

2. Trace metal concentrations in water samples

- Systematic analytical error for all of the trace metals: < below 9% except for two trace metals (Zn and Fe: 32.9% and 26.2%, respectively)

- Ti concentrations range between 26.5 µg/L and 200.2 µg/L (average measured Ti concentration in major world rivers (Gaillardet et al., 2003): 0.489 µg/L)

3. Trace metal concentrations in sediment samples

- Sediment characteristics: predomi nantly quartzose sand and silt with minor amounts of gravel and clay

- ICP-MS analyses (geostandard analytical error: < 10% ) of Ti concentratrions: 1289 -5359 mg/kg bulk sediment (mean concentration: 3461.95 mg/kg bulk sediment; Ti background concentration based on average crustal shale: 4600 (see Turekian, 1972))

- Highest amounts of Ti in carbonate fraction and residual fraction of sediments

Validity criteria fulfilled:
not applicable
Conclusions:
The mean (for 20 locations) log Kd for sediment is 4.61 L/kg dw.
Executive summary:

The authors examined the partitioning behaviour of Ti and other trace metals between surface water and sediments and their environmental fate within the sediments. Water and sediment samples for the experiment were taken from 20 randomly chosen sites of the Blesbokspruit, a riparian wetland near Johannesburg, South Africa, which is affected by mining activities.

Concentrations of Ti were measured in the sediment samples as well as in the water phase. The partition coefficient Kd is calculated as follows (equilibrium is assumed):

Kd = Cs/Cw, with:

Cs = Ti concentration in the solid phase;

Cw = Ti concentration in the water phase.

The mean log Kd for sediment is 4.61 L/kg dw (range: 3.79-5.13).

Endpoint:
adsorption / desorption
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Documentation insufficent for assessment with regard to results reported for Ti (sufficient detail levels for other trace elements investigated in this study). Justification for read-across: No data on the behavior of titanium carbide in the environment are available. Concentration data for titanium metal are appropriate for read-across for this endpoint as the soluble species released are expected to be similar for each of the compounds, and are thus expected to behave similarly in the environment. For more details refer to the attached description of the read across approach.
Qualifier:
no guideline followed
Principles of method if other than guideline:
The authors examined the partitioning behaviour of Ti and other trace metals between surface water and suspended matter. Water and sediment samples for the experiment were taken from 54 Czech rivers at 119 locations.

Concentrations of Ti were measured in suspended matter as well as in the water phase. The partition coefficient Kd is calculated as follows (equilibrium is assumed):

Kd = Cs/Cl, with:
Cs = Ti concentration in suspended matter;
Cl = Ti concentration in the liquid phase.
GLP compliance:
not specified
Type of method:
other:
Media:
other: suspended solids
Radiolabelling:
not specified
Test temperature:
not reported
Analytical monitoring:
yes
Details on sampling:
- 0.4µm-filtered and unfiltered water samples were collected under stable hydrological conditions; filtration was done in the field
- Samples for HPLC, ISE, FAAS, GFAAS and ICP-MS were cooled and transported to the laboratory for analysis
- Samples for FAAS, GFAAS and ICP-MS were acidified to pH 1.5 (> 1 ml HNO3)
- Prior to sampling vessels were cleaned with 10% HNO3 for at least 2 days; in addition filters and hand pump filter system were cleaned by means of HNO3 and distilled water prior to use in the field
- Sampling volume: 200 ml per sampling site were filtered; additional 100 ml of each sample required for analysis in the laboratory
Key result
Phase system:
solids-water in suspended matter
Type:
log Kp
Value:
2.36 L/kg
Remarks on result:
other: median for samples from 54 rivers in 119 locations
Transformation products:
no

1. Surface water samples

- Mean pH: 7.74 (range 6.9-8.8)

- Ionic strength I: 7.8 mmol/L

- Electric conductivity: 538 µS/cm at 25 °C

- Alkalinity (ANC): 1.9 mmol/L

- Suspended particulate matter: 9.9 mg/L (range: 1.0-124 mg/L)

Mean concentrations of major solutes and main SPM components

 

Dissolved fraction [mg/L]a

SPM [%]

Al

< 0.2

3.96

Ca

47.7

1.51

Cl

35.1

0.30

F

0.22

-c

Fe

0.31

4.66

K

6.32

1.42

Mg

14.6

-

Mn

0.13

0.28

Na

30.8

0.81

P

-

0.54

S-SO4

29.4

0.26

Si

4.91

14.4

Ti

 

0.33

DOC/POMb

5.65

(47)

aDissolved fraction = filtered water = true solution + colloids

bParticulate organic matter (POM): calculated as residue

c– Not determined

- Influence of DOC: for Ti increasing DOC resulted in decreasing Kd values (range not reported)

Validity criteria fulfilled:
not applicable
Conclusions:
The median (n=119) for the Ti log Kd for suspended matter is 2.36 L/kg dw.
Executive summary:

The authors examined the partitioning behaviour of Ti and other trace metals between surface water and suspended matter. Water and sediment samples for the experiment were taken from 54 Czech rivers at 119 locations.

Concentrations of Ti were measured in suspended matter as well as in the water phase. The partition coefficient Kd is calculated as follows (equilibrium is assumed):

Kd = Cs/Cl, with:

Cs = Ti concentration in suspended matter;

Cl = Ti concentration in the liquid phase.

The median for the Ti log Kd for suspended matter is 2.36 L/kg dw.

Endpoint:
adsorption / desorption
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Secondary source. Original data (Li, 2000) not available. Results are reported in Roychoudhury & Starke (2006). Justification for read-across: No data on the behavior of titanium carbide in the environment are available. Concentration data for titanium metal are appropriate for read-across for this endpoint as the soluble species released are expected to be similar for each of the compounds, and are thus expected to behave similarly in the environment. For more details refer to the attached description of the read across approach.
Reason / purpose for cross-reference:
reference to other study
Qualifier:
no guideline followed
Principles of method if other than guideline:
No data. Secondary source, results from Li (2000) cited in Roychoudhury & Starke (2006).
GLP compliance:
not specified
Type of method:
other: No data, secondary source.
Media:
sediment
Radiolabelling:
not specified
Test temperature:
No data, secondary source.
Analytical monitoring:
not specified
Key result
Phase system:
solids-water in sediment
Type:
log Kp
Value:
5.75 L/kg
Remarks on result:
other: World average for riverine environments.
Validity criteria fulfilled:
not specified
Conclusions:
The world average partition coefficient (log Kp in L/kg) for Ti is reported to be 5.75.
Executive summary:

Roychoudhury & Starke (2006) cite the world average partition coefficient (log Kp in L/kg) for Ti (reported in Li, 2000) to be 5.75.

Endpoint:
adsorption / desorption
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Key result
Phase system:
solids-water in suspended matter
Type:
log Kp
Value:
2.36 L/kg
Remarks on result:
other: median for samples from 54 rivers in 119 locations
Transformation products:
no

1. Surface water samples

- Mean pH: 7.74 (range 6.9-8.8)

- Ionic strength I: 7.8 mmol/L

- Electric conductivity: 538 µS/cm at 25 °C

- Alkalinity (ANC): 1.9 mmol/L

- Suspended particulate matter: 9.9 mg/L (range: 1.0-124 mg/L)

Mean concentrations of major solutes and main SPM components

 

Dissolved fraction [mg/L]a

SPM [%]

Al

< 0.2

3.96

Ca

47.7

1.51

Cl

35.1

0.30

F

0.22

-c

Fe

0.31

4.66

K

6.32

1.42

Mg

14.6

-

Mn

0.13

0.28

Na

30.8

0.81

P

-

0.54

S-SO4

29.4

0.26

Si

4.91

14.4

Ti

 

0.33

DOC/POMb

5.65

(47)

aDissolved fraction = filtered water = true solution + colloids

bParticulate organic matter (POM): calculated as residue

c– Not determined

- Influence of DOC: for Ti increasing DOC resulted in decreasing Kd values (range not reported)

Validity criteria fulfilled:
not applicable
Conclusions:
The median (n=119) for the Ti log Kd for suspended matter is 2.36 L/kg dw.
Executive summary:

The authors examined the partitioning behaviour of Ti and other trace metals between surface water and suspended matter. Water and sediment samples for the experiment were taken from 54 Czech rivers at 119 locations.


 


Concentrations of Ti were measured in suspended matter as well as in the water phase. The partition coefficient Kd is calculated as follows (equilibrium is assumed):


 


Kd = Cs/Cl, with:


Cs = Ti concentration in suspended matter;


Cl = Ti concentration in the liquid phase.


 


The median for the Ti log Kd for suspended matter is 2.36 L/kg dw.


This information is used in a read-across approach in the assessment of the target substance. For justification of read-across please refer to the attached read-across report (see IUCLID section 13). 

Endpoint:
adsorption / desorption: screening
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Justification for read-across: Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. Therefore, the dose descriptors are expected to be sufficiently higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read-across approach (see IUCLID section 13.2).
Reason / purpose for cross-reference:
read-across source
Key result
Phase system:
solids-water in sediment
Type:
log Kp
Value:
4.61 L/kg
Remarks on result:
other: mean log Kp value for 20 locations, range: 3.79-5.13
Transformation products:
no
Details on results (Batch equilibrium method):
See "Any other infromation on results incl. tables".
Statistics:
The partition coefficient Kd is calculated as follwos (equilibrium is assumed):
Kd = Cs/Cw,
with Cs = Ti concentration in the solid phase; Cw = Ti concentration in the water phase

1. Surface water samples

- pH: neutral to alkaline (pH 7-9.2) due to dolomitic bedrock

- Dissolved oxygen: 2.5–10.8 mg/L

- Electric conductivity: 521-2400 µS/cm (differences attributed to location of sampling point above or below discharge point of the Grootvlei mine effluent)

- Dominant anions: chloride (28-161 mg/L) and sulphate (73-702 mg/L)

- Dominant cations: Na+ (69-855 mg/L) and Ca+ (21 -195 mg/L)

- Charge balance was for all samples in the range of 0.1 -9.8 % (thus below the acceptable value of 10 %) ecept for one site where major cations were underestimated (imbalance: 29 %)

2. Trace metal concentrations in water samples

- Systematic analytical error for all of the trace metals: < below 9% except for two trace metals (Zn and Fe: 32.9% and 26.2%, respectively)

- Ti concentrations range between 26.5 µg/L and 200.2 µg/L (average measured Ti concentration in major world rivers (Gaillardet et al., 2003): 0.489 µg/L)

3. Trace metal concentrations in sediment samples

- Sediment characteristics: predomi nantly quartzose sand and silt with minor amounts of gravel and clay

- ICP-MS analyses (geostandard analytical error: < 10% ) of Ti concentratrions: 1289 -5359 mg/kg bulk sediment (mean concentration: 3461.95 mg/kg bulk sediment; Ti background concentration based on average crustal shale: 4600 (see Turekian, 1972))

- Highest amounts of Ti in carbonate fraction and residual fraction of sediments

Validity criteria fulfilled:
not applicable
Conclusions:
The mean (for 20 locations) log Kd for sediment is 4.61 L/kg dw.
Executive summary:

The authors examined the partitioning behaviour of Ti and other trace metals between surface water and sediments and their environmental fate within the sediments. Water and sediment samples for the experiment were taken from 20 randomly chosen sites of the Blesbokspruit, a riparian wetland near Johannesburg, South Africa, which is affected by mining activities.


 


Concentrations of Ti were measured in the sediment samples as well as in the water phase. The partition coefficient Kd is calculated as follows (equilibrium is assumed):


 


Kd = Cs/Cw, with:


Cs = Ti concentration in the solid phase;


Cw = Ti concentration in the water phase.


 


The mean log Kd for sediment is 4.61 L/kg dw (range: 3.79-5.13).


This information is used in a read-across approach in the assessment of the target substance. For justificcation of read-across please refer to the attached read-across report (see IUCLID section 13).

Endpoint:
adsorption / desorption
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Reason / purpose for cross-reference:
reference to other study
Key result
Phase system:
solids-water in sediment
Type:
log Kp
Value:
5.75 L/kg
Remarks on result:
other: World average for riverine environments.
Validity criteria fulfilled:
not specified
Conclusions:
The world average partition coefficient (log Kp in L/kg) for Ti is reported to be 5.75.
Executive summary:

Roychoudhury & Starke (2006) cite the world average partition coefficient (log Kp in L/kg) for Ti (reported in Li, 2000) to be 5.75.


This information is used in a read-across approach in the assessment of the target substance. For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Description of key information

Based on the available data for titanium, titanium compounds like titanium carbide are expected to have a very low mobility in soil. 

Key value for chemical safety assessment

Other adsorption coefficients

Type:
log Kp (solids-water in sediment)
Value in L/kg:
4.61

Additional information

Roychoudhury and Starke (2006) examined the partitioning behaviour of Ti between surface water and riverine sediments. Concentrations of Ti were measured in the sediment samples as well as in the water phase. The mean log Kd for sediment is 4.61 L/kg dw (range: 3.79-5.13), which is within the same order of magnitude as the world average partition coefficient (log Kp in L/kg) for Ti of 5.75 reported by Li (2000).

Vesely et al. (2001), who examined the partitioning behaviour of Ti between surface water and suspended matter, report a lower log Kd for suspended matter of 2.36 L/kg dw. However, the publication is not considered reliable due to deficiencies in documentation. Therefore, this result is not further considered in the assessment.

In conclusion, based on the available data for titanium, titanium compounds like titanium carbide are expected to have a very low mobility in soil.