Calcium acetylide

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Type of information:

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

Adequacy of study:

key study

Study period:

2000

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Justification for type of information:

As calcium carbide instantly hydrolyses to Ca(OH)2 and C2H2 upon contact with water/moisture the assessment is based on the degradation products. For details please refer to the read across report in section 13.

Reason / purpose for cross-reference:

read-across source

Key result

Sample No.:

#1

Type:

Kd

Value:

37.6 L/kg

pH:

5.1

% Org. carbon:

ca. 0

Key result

Sample No.:

#2

Type:

Kd

Value:

41.96 L/kg

pH:

5.1

% Org. carbon:

ca. 0

Key result

Sample No.:

#3

Type:

Kd

Value:

49.1 L/kg

pH:

5.1

% Org. carbon:

ca. 0

Key result

Sample No.:

#4

Type:

Kd

Value:

5.3 L/kg

pH:

5.1

% Org. carbon:

ca. 0

Key result

Sample No.:

#5

Type:

Kd

Value:

16.97 L/kg

pH:

5.1

% Org. carbon:

ca. 0

Adsorption and desorption constants:

Experiment 1:
- Sample 1:
* Sorbed: 0.0564 cmolc Ca/kg
* Not-sorbed: 15.0 µmol Ca/L
* Kd: 37.6 l/kg

- Sample 2:
* Sorbed: 0.0944 cmolc Ca/kg
* Not-sorbed: 22.5 µmol Ca/L
* Kd: 41.96 l/kg

- Sample 3:
* Sorbed: 0.106 cmolc Ca/kg
* Not-sorbed: 21.6 µmol Ca/L
* Kd: 49.1 l/kg

- Sample 4:
* Sorbed: 0.0284 cmolc Ca/kg
* Not-sorbed: 53.4 µmol Ca/L
* Kd: 5.3 l/kg

Experiment 2:
The Kd was only calculated for the 0.218 mM CaCl2 (total Ca2+ in system: 244.6 µmol/L; adsorption experiment at soil pH, i.e. at a pH of ca. 5.1):
* Sorbed: 31.74 mg Ca/kg
* In solution: 1.87 mg Ca/L
* Kd: 16.97 l/kg.

Transformation products:

not measured

Validity criteria fulfilled:

not applicable

Conclusions:

Kd values were calculated for the adsorption of Ca2+ to soil particles from the B horizon of a podzolized soil.
In the first step, Ca2+ in soil solution and extractable Ca2+ was measured in 4 centrifuged samples of the soil. Respective Kd values range between 5.3 and 49.1 L/kg.
In the second step, the B2 horizon of the same soil was treated with different solutions (with or without CaCl2 and/or HCl). The respective Kd value was calculated to be 16.97 L/kg at a pH of approximately 5.1.

Executive summary:

In this experiment the soil water from the B2 horizon of Hyytiälä soil (podzolised soil) was analysed after centrifugation from soil samples for (amongst others) the concentration of Ca2+ cations (analysis were conducted on several samples obtained at 4 sampling occasions) in a first step (=experiment 1). In addition, extractable Ca2+ was measured by bulking the centrifuges samples, and subsequent extraction with BaCl2.

In a second step (=experiment 2), batch equilibrium experiments were conducted to determine the adsorption and desorption of Ca in the B2 horizon of the Hyytiälä soil: 2 g of soil was shaken for 8 days with 20 mL of different solutions with or without Ca (0.218 mM CaCl2) and increasing pH levels.

Subsequently, Kd values were calculated for the adsorption of Ca2+ to soil particles from the B horizon. In the first experiment Kd values range between 5.3 and 49.1 L/kg. In the second experiment, the Kd value was calculated to be 16.97 L/kg.

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 read-across report attached to IUCLID section 13.

Reference 2

Endpoint:

adsorption / desorption: screening

Type of information:

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

Adequacy of study:

key study

Study period:

2001

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Justification for type of information:

As calcium carbide instantly hydrolyses to Ca(OH)2 and C2H2 upon contact with water/moisture the assessment is based on the degradation products. For details please refer to the read across report in section 13.

Reason / purpose for cross-reference:

read-across source

Radiolabelling:

no

Key result

Sample No.:

#1

Type:

Kd

Value:

11.3 L/kg

Temp.:

20 °C

Remarks on result:

other: No data on organic carbon content.

Adsorption and desorption constants:

Kd = 11.3 L/kg for Ca2+
Log Kd = 1.05

Transformation products:

not measured

Details on results (Batch equilibrium method):

The soil pH changed quickly (less than 5 min) when treated with the leachate (pH = 12) to an equilibrium value (pH = 6.5).
For equilibrium, for the experimental conditions used (ratio soil/leachate 1/4), the distribution coefficients between the soil and the
liquid leachate could be established for Ca2+: Kd = 11.3 L/kg.

Validity criteria fulfilled:

not applicable

Conclusions:

Batch equilibrium experiments were performed with agricultural soil and a leachate obtained from sewage sludge. The leachate was obtained by simulating rainfall on lime-stabilized (20 % CaO) sludge.
In the course of the 6-h batch equilibrium experiment, Ca2+ cations from the leachate were adsorbed to soil particles.
The respective Kd value for Ca2+ was calculated to be 11.3 L/kg.
Although the pH of the leachate was quite high due to the added lime, the high buffer capacity of the soil maintained the soil pH.

Executive summary:

The aim of this study was to investigate the effect of an industrial lime-stabilized sludge deposited on an acid soil.

In a first step a leachate form the sludge was obtained by simulating leaching due to rainfall from sludge deposited over soil. The leachate was then analysed for its cation composition (Ca, Na, K, Mg, Ni, Zn).

In a second step batch equilibrium experiments were performed to investigate the adsorption behaviour of the cations from the leachate to soil particles during a 6 hour time period.

In the course of the 6-h batch equilibrium experiment, Ca2+ cations from the leachate were adsorbed to soil particles. The respective Kd value for Ca2+ was calculated to be 11.3 L/kg.

Although the pH of the leachate was quite high due to the added lime, the high buffer capacity of the soil maintained the soil pH.

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 read-across report attached to IUCLID section 13.

Reference 3

Endpoint:

adsorption / desorption: screening

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance has a low octanol water partition coefficient and the adsorption potential of this substance is related to this parameter

Reference 4

Endpoint:

adsorption / desorption: screening

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance and its relevant degradation products decompose rapidly

Description of key information

In contact with water/soil moisture calcium carbide instantly hydrolysis to calcium hydroxide and acetylene. Thus these two compounds are relevant in for the assessment of the environmental fate.

Additional information

In contact with water/soil moisture calcium carbide instantly hydrolysis to calcium hydroxide and acetylene. Thus these two compounds are relevant in the assessment of the environmental fate.

Calcium hydoxide:

Two studies are publically available that investigate the adosrption/desorption behaviour of calcium to soil.

In the first study the adsoprtion of Ca2+ to the B2 horizon of podzolided soil was determined. Repsective Kd values range between 5.3 and 49.1 L/kg.

In the second experiment, the Kd value of Ca2+ adsorption to soil particles was calculated to be 11.3 L/kg and thus is within the range of the Kd values determined in the first study.

It can be concluded that the adsorption of Ca+2 to soil is rather low.

Acetylene has a very low log Kow (0.37). In addition, the substance is a gas with high vapour pressure and high Henry Law constant¹ and will not remain in the water phase/soil pore water. Thus, significant adsorption of acetylene to soil and sediments is not expected.

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 read-across report attached to IUCLID section 13.

¹Solubilty in water: 1200 mg/L; vapour pressure: 4.04 x 10^4 mm Hg at 25 °C (Daubert, T.E., R.P. Danner. Physical and Thermodynamic Properties of Pure Chemicals Data Compilation. Washington, D.C.: Taylor and Francis, 1989; cited in HSDB)

=> approximate Henry Law constant = vapour pressure/ aqueous solubility = 5386224 Pa / 46.08 mol/m³ = ~ 116,900 Pa m³/mol