Quaternary ammonium compounds, di-C12-18-alkyldimethyl, chlorides

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

19 Mar, 2008 - 30 Aug, 2008

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

This study result has been assigned a validity of 2, due to the very high concentrations of the test substance used (0.5 g test substance for 1 g soil) causing extrapolations to lower concentrations to be less accurate. (Adsorption is likely to be higher at lower concentrations than suggested by the outcome of this study).

Qualifier:

according to guideline

Guideline:

OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Test temperature:

20 °C

Analytical monitoring:

yes

Key result

Type:

Koc

Value:

ca. 280 547 L/kg

% Org. carbon:

>= 3.29

Remarks on result:

other: Soil 1

Key result

Type:

Koc

Value:

ca. 120 000 L/kg

% Org. carbon:

ca. 2.39

Remarks on result:

other: Soil 2

Key result

Type:

Koc

Value:

ca. 43 855 L/kg

% Org. carbon:

ca. 3.32

Remarks on result:

other: Soil 3

Key result

Type:

Koc

Value:

ca. 160 882 L/kg

% Org. carbon:

ca. 1.36

Remarks on result:

other: Soil 4

Key result

Type:

Koc

Value:

ca. 40 339 L/kg

% Org. carbon:

ca. 4.43

Remarks on result:

other: Soil 5

Key result

Type:

Kd

Value:

ca. 9 230 L/kg

Remarks on result:

other: Soil 1

Key result

Type:

Kd

Value:

ca. 2 868 L/kg

Remarks on result:

other: Soil 2

Key result

Type:

Kd

Value:

ca. 1 456 L/kg

Remarks on result:

other: Soil 3

Key result

Type:

Kd

Value:

ca. 2 188 L/kg

Remarks on result:

other: Soil 4

Key result

Type:

Kd

Value:

ca. 1 787 L/kg

Remarks on result:

other: Soil 5

Preliminary studies confirmed that there was no adsorption to the apparatus or filter material and stability of the test item in the pH range of selected soils. A preliminary mass balance showed recoveries of ca. 90 %. Therefore, both aqueous and soil phase were analysed in the definitive study.

Based on the results of preliminary tests 100, 500, 1000, 5000 and 10000 mg/L were selected as nominal test substance concentrations for adsorption/desorption isotherms for all tested soils. The concentrations of the test substance were determined in CaCl2 solution via spectrophotometry after formation of an ion pair with an azo dye and subsequent extraction. The concentration adsorbed to soil was then determined by calculation.

Under the test conditions didecyldimethylammonium chloride (DDAC) demonstrated a high tendency to adsorb to the five test soils. There was no correlation between the degree of adsorption and the organic carbon content of the soil. This suggest that other mechanisms were involved in the adsorption of DDAC (e.g. interactions with the inorganic matter of the
soil). 

Desorption was also very low (3 - 23 %). For ail soils and test concentrations, the mass balance was < 90 %.
This could be caused by non-extractable residues which means irreversible adsorption.

Therefore, on the basis of these results, DDAC can be considered immobile in soil.


Freundlich (Kads(F) isotherm for adsorption:
Euro   log     1/n     r^2
soil  Kads(F)
____________________________
1    3.9652  0.4447  0.9947
2    3.4576  0.5715  0.9855
3    3.1632  0.4739  0.9528 
4    3.3400  0.6248  0.9738 
5    3.2521  0.4582  0.9651 

Freundlich (Kdes(F) isotherm for desorption:
Euro   log    1/n      r^2
soil  Kdes(F)    
_____________________________
1    3.5703  0.8048  0.9920
2    3.6271  0.7288  0.9947
3    3.3257  0.6390  0.9753
4    3.4998  0.6386  0.9851
5    3.3779  0.5815  0.9848

Desorption coefficient Kdes and Freundlich desorption
coefficient Fdes(F):

            Soil 1 soil 2  soil 3  soil 4 soil 5
________________________________________________
%desorption    3      11      23      18     15
Kdes        1900     414     175     232    295
Fdes(F)     3718    4237    2117    3161   2387

Validity criteria fulfilled:

yes

Conclusions:

Under the study conditions, the average Koc of the test substance was determined to be 129125 L/kg, indicating high adsorption potential and low mobility.

Executive summary:

A study was conducted to determine the adsorption / desorption of the read across substance, DDAC (40.37% active) using the batch equilibrium, according to OECD Guideline 106, in compliance with GLP.

The amount adsorbed on soils was calculated from depletion of the test substance in the overlaying solution (indirect method). The soils used were EURO-soil standard numbers 1, 2, 3, 4 and 5. The soil/solution ratio was 1:50 (1.0 g soil and 50 mL solution). Based on the results of preliminary tests, 100, 500, 1000, 5000 and 10000 mg/L were selected as nominal concentrations. The concentration of test substance in solution was determined via spectrophotometry. The concentration adsorbed to the soil was then determined by calculation. Under the study conditions, the test substance can be considered as immobile in five soil types. The adsorption mobility (Kaoc) and desorption mobility (Kdoc) coefficients were in the range 40339 to 280547 L/kg and 53883 to 232426 L/kg respectively. Based on the Kd values and organic carbon percentage, the respective Koc values were determined as follows:

Soil type	% Organic carbon	CEC (mval/100g)	Adsorption			Desorption
			Ka (L/kg)	1/na	KaOC (L/kg)	Kd (L/kg)	1/nd	KdOC (L/kg)	Ka/Kd
Euro soil 1: clay	3.29	32.4	9230	0.4447	280547	3718	0.8048	113009	2.48
Euro soil 2: silt loam	28.9	28.9	2868	0.5715	120000	4237	0.7288	177280	0.68
Euro soil 3: loam	16.6	16.6	1456	0.4739	43855	2117	0.6390	63765	0.69
Euro soil 4: silt	17.3	17.3	2188	0.6248	160882	3161	0.6386	232426	0.69
5: loamy sand	24.1	24.1	1787	0.4582	40339	2387	0.5815	53883	0.75

Ka = Adsorption coefficient; Kaoc = Adsorption coefficient based on organic carbon content; Kd=Desorption coefficient; Kdoc = Desorption coefficient based on organic carbon content; Ka/Kd = Adsorption / Desorption distribution coefficient

The 1/n values indicate that a non-linear relationship exists between the concentrations in soil and the concentrations the water. DDAC adsorbs strongly onto soil and does not desorb very easily for all soil types (2-3%). Based on these results, it can be concluded that the substance is immobile in soil (Geffke, 2002). It is well known that, because of their positive charge, cationic surfactants adsorb strongly to the negatively charged surfaces of sludge, soil and sediments. The average Koc is 129125 L/kg.

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:

19 Mar, 2008 - 30 Aug, 2008

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

This study result has been assigned a validity of 2, due to the very high concentrations of the test substance used (0.5 g test substance for 1 g soil) causing extrapolations to lower concentrations to be less accurate. (Adsorption is likely to be higher at lower concentrations than suggested by the outcome of this study).

Justification for type of information:

Refer to section 13 of IUCLID for details on the read-across justification. The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Test temperature:

20 °C

Analytical monitoring:

yes

Key result

Type:

Koc

Value:

ca. 280 547 L/kg

% Org. carbon:

>= 3.29

Remarks on result:

other: Soil 1

Key result

Type:

Koc

Value:

ca. 120 000 L/kg

% Org. carbon:

ca. 2.39

Remarks on result:

other: Soil 2

Key result

Type:

Koc

Value:

ca. 43 855 L/kg

% Org. carbon:

ca. 3.32

Remarks on result:

other: Soil 3

Key result

Type:

Koc

Value:

ca. 160 882 L/kg

% Org. carbon:

ca. 1.36

Remarks on result:

other: Soil 4

Key result

Type:

Koc

Value:

ca. 40 339 L/kg

% Org. carbon:

ca. 4.43

Remarks on result:

other: Soil 5

Key result

Type:

Kd

Value:

ca. 9 230 L/kg

Remarks on result:

other: Soil 1

Key result

Type:

Kd

Value:

ca. 2 868 L/kg

Remarks on result:

other: Soil 2

Key result

Type:

Kd

Value:

ca. 1 456 L/kg

Remarks on result:

other: Soil 3

Key result

Type:

Kd

Value:

ca. 2 188 L/kg

Remarks on result:

other: Soil 4

Key result

Type:

Kd

Value:

ca. 1 787 L/kg

Remarks on result:

other: Soil 5

Preliminary studies confirmed that there was no adsorption to the apparatus or filter material and stability of the test item in the pH range of selected soils. A preliminary mass balance showed recoveries of ca. 90 %. Therefore, both aqueous and soil phase were analysed in the definitive study.

Based on the results of preliminary tests 100, 500, 1000, 5000 and 10000 mg/L were selected as nominal test substance concentrations for adsorption/desorption isotherms for all tested soils. The concentrations of the test substance were determined in CaCl2 solution via spectrophotometry after formation of an ion pair with an azo dye and subsequent extraction. The concentration adsorbed to soil was then determined by calculation.

Under the test conditions didecyldimethylammonium chloride (DDAC) demonstrated a high tendency to adsorb to the five test soils. There was no correlation between the degree of adsorption and the organic carbon content of the soil. This suggest that other mechanisms were involved in the adsorption of DDAC (e.g. interactions with the inorganic matter of the
soil). 

Desorption was also very low (3 - 23 %). For ail soils and test concentrations, the mass balance was < 90 %.
This could be caused by non-extractable residues which means irreversible adsorption.

Therefore, on the basis of these results, DDAC can be considered immobile in soil.


Freundlich (Kads(F) isotherm for adsorption:
Euro   log     1/n     r^2
soil  Kads(F)
____________________________
1    3.9652  0.4447  0.9947
2    3.4576  0.5715  0.9855
3    3.1632  0.4739  0.9528 
4    3.3400  0.6248  0.9738 
5    3.2521  0.4582  0.9651 

Freundlich (Kdes(F) isotherm for desorption:
Euro   log    1/n      r^2
soil  Kdes(F)    
_____________________________
1    3.5703  0.8048  0.9920
2    3.6271  0.7288  0.9947
3    3.3257  0.6390  0.9753
4    3.4998  0.6386  0.9851
5    3.3779  0.5815  0.9848

Desorption coefficient Kdes and Freundlich desorption
coefficient Fdes(F):

            Soil 1 soil 2  soil 3  soil 4 soil 5
________________________________________________
%desorption    3      11      23      18     15
Kdes        1900     414     175     232    295
Fdes(F)     3718    4237    2117    3161   2387

Validity criteria fulfilled:

yes

Conclusions:

Based on the results of the read across study, the average Koc of the test substance was determined to be 129125 L/kg, indicating high adsorption potential and low mobility.

Executive summary:

A study was conducted to determine the adsorption / desorption of the read across substance, DDAC (40.37% active) using the batch equilibrium, according to OECD Guideline 106, in compliance with GLP.

The amount adsorbed on soils was calculated from depletion of the test substance in the overlaying solution (indirect method). The soils used were EURO-soil standard numbers 1, 2, 3, 4 and 5. The soil/solution ratio was 1:50 (1.0 g soil and 50 mL solution). Based on the results of preliminary tests, 100, 500, 1000, 5000 and 10000 mg/L were selected as nominal concentrations. The concentration of test substance in solution was determined via spectrophotometry. The concentration adsorbed to the soil was then determined by calculation. Under the study conditions, the test substance can be considered as immobile in five soil types. The adsorption mobility (Kaoc) and desorption mobility (Kdoc) coefficients were in the range 40339 to 280547 L/kg and 53883 to 232426 L/kg respectively. Based on the Kd values and organic carbon percentage, the respective Koc values were determined as follows:

Soil type	% Organic carbon	CEC (mval/100g)	Adsorption			Desorption
			Ka (L/kg)	1/na	KaOC (L/kg)	Kd (L/kg)	1/nd	KdOC (L/kg)	Ka/Kd
Euro soil 1: clay	3.29	32.4	9230	0.4447	280547	3718	0.8048	113009	2.48
Euro soil 2: silt loam	28.9	28.9	2868	0.5715	120000	4237	0.7288	177280	0.68
Euro soil 3: loam	16.6	16.6	1456	0.4739	43855	2117	0.6390	63765	0.69
Euro soil 4: silt	17.3	17.3	2188	0.6248	160882	3161	0.6386	232426	0.69
5: loamy sand	24.1	24.1	1787	0.4582	40339	2387	0.5815	53883	0.75

Ka = Adsorption coefficient; Kaoc = Adsorption coefficient based on organic carbon content; Kd=Desorption coefficient; Kdoc = Desorption coefficient based on organic carbon content; Ka/Kd = Adsorption / Desorption distribution coefficient

The 1/n values indicate that a non-linear relationship exists between the concentrations in soil and the concentrations the water. DDAC adsorbs strongly onto soil and does not desorb very easily for all soil types (2-3%). Based on these results, it can be concluded that the substance is immobile in soil (Geffke, 2002). It is well known that, because of their positive charge, cationic surfactants adsorb strongly to the negatively charged surfaces of sludge, soil and sediments. The average Koc is 129125 L/kg. Based on the results of the read across study, a similar high adsorption potential can be expected for the test substance.

Reference 3

Endpoint:

adsorption / desorption: screening

Remarks:

adsorption

Type of information:

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

Adequacy of study:

supporting study

Study period:

1983

Reliability:

2 (reliable with restrictions)

Justification for type of information:

Refer to section 13 of IUCLID for details on the read-across justification. The study with the read across substance is considered sufficient to fulfil the information requirements.

Reason / purpose for cross-reference:

read-across source

Principles of method if other than guideline:

The sorption potential of the 14C-radiolabeled test substance, C18 DAQ (>95% active) was determined in standard EPA sediment (EPA 18) and two river sediments from Rapid creek and Ohio river).

GLP compliance:

not specified

Type of method:

other: Adsorption was measured using a liquid scintillation counter

Media:

sediment

Radiolabelling:

yes

Test temperature:

No details given

Details on study design: HPLC method:

Not relevant

Analytical monitoring:

yes

Details on sampling:

No details supplied

Details on matrix:

Collected from two rivers (Rapid creek, Rapid City, SD; Ohio River, Cincinnati, OH) at locations 0.5 to 1.0 mile below the discharge of municipal wastewater treatment treatment plants. The sites varied significantly in terms of hydrological/geological characteristics. Rapid creek is a slow-flowing mountain stream (mean discharge ~ 50 ft3/s) with a low wastewater dilution factor (~1:5-1:10), whereas the Ohio River is a rapidly flowing major river (mean discharge ~2000,000 ft3) with high wastewater dilution factor (>1:10,000). Sediment samples were analysed for cation exchange capacity (CEC), pH, particle distribution, organic carbon, and suspended solids levels by standard procedures. They were tested on a dry weight basis. Compartive data for the two river sediments and a standard EPA sediment (EPA 18) are given in Table 1.

Details on test conditions:

Mixtures of test chemical and sediment were placed into 220 ml beakers containing 150-200 ml of 0.01 M KCl buffer. the beakers were agitated on a rotary platform shaker at room temperature to maintain uniform solids suspensions and at various intervals aliquots were removed and centrifuged at 39,000 xg for 30 min to remove particulate matter. The amount of radioactivity in solution, or on the solids after combustion, was then quantitated by liquid scintillation counting (LSC)
and expressed as Kd, the solid/solution partition coefficient, as follows:

Kd = Csolids/Csolution -------- Eq (1)

Where:
Csolids = ug/g on the solids
Csolution = ug/mL in solution

Eq (1) is a modified form of the Freundlich isotherm:
Csolids = Kd x Csolution x 1/n ----------------- Eq (2)

which is generally used to model adsorption processes. The Kd value can be derived from equation (2) when n = 1 and can be extrapolated to different sediments by normalizing for the organic carbon content of the sediment.

Computational methods:

Csolids

C solids
K2 = ____________
C solution

where: Csolids = ug/g on the solids

Csolution = ug/ml in solution

Equation (1) is a modified form of the Freundlich isotherm

Csolids = KdCsolution l/n

which is generally used to model adsorption processes. the Kd value can be derived from equation 2 when n=1 and can be extrapolated to different sediments by normalising for the organic carbon content of the sediment.

Key result

Phase system:

other: Kd (sediment-water)

Type:

other: Kd (sediment-water)

Value:

12 489 L/kg

Remarks on result:

other: EPA 18 sediment

Key result

Phase system:

other: Kd (sediment-water)

Type:

other: Kd (sediment-water)

Value:

3 833 L/kg

Remarks on result:

other: Ohio river sediment

Key result

Phase system:

other: Kd (sediment-water)

Type:

other: Kd (sediment-water)

Value:

10 775 L/kg

Remarks on result:

other: Rapid creek sediment

Recovery of test material:

N

Transformation products:

not specified

Statistics:

No details given

Validity criteria fulfilled:

not specified

Conclusions:

Based on the results of the read across study, the Kd values for the three sediments were determined to be 3833 (Ohio river), 10775 (Rapid creek) and 12489 (EPA 18) L/kg, indicating high adsorption potential or low mobility.

Executive summary:

A study was conducted to determine the sorption potential of the 14C-radiolabeled read across substance, C18 DAQ (>95% active) in standard EPA sediment (EPA 18) and two river sediments from Rapid creek and Ohio river. Mixtures of test substance and sediment were placed into 220 mL beakers containing 150-200 mL of 0.01 M KCl buffer. The beakers were agitated on a rotary platform shaker at room temperature to maintain uniform solids suspensions and at various intervals aliquots were removed and centrifuged at 39,000 xg for 30 min to remove particulate matter. The amount of radioactivity in solution, or on the solids after combustion, was then quantitated by liquid scintillation counting (LSC). The Kd values for the three sediments were determined to be 3833 (Ohio river), 10775 (Rapid creek) and 12489 (EPA 18) L/kg (see below table):

Sediment	% Organic carbon	% Sand	% Clay	% Silt	CEC (meg/100g)	pH	Kd (L/kg)
EPA18	0.7	34.6	39.5	25.8	15.4	7.8	12489
Ohio river	2.0	28.0	39.7	32.4	18.4	--	3833
Rapid Creek	3.5	0.2	2.4	97.4	15.7	7.1	10775

 

Under the conditions, of the study, the test substance is considered to have high adsorption potential to sediment and soil (Larson and Vashon, 1983). Based on the results of the read across study, a similar high adsorption potential is expected for the test substance.

Reference 4

Endpoint:

adsorption / desorption

Remarks:

adsorption

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1983

Reliability:

2 (reliable with restrictions)

Principles of method if other than guideline:

- Uniform alkyl-labeled 14 C-DSDMAC was synthesized in our laboratories with a specific activity of 3 .2 μCi/mg (1.9 mCi/mmol). Radiochemical purity was >95%, as determined by TLC and HPLC.

GLP compliance:

not specified

Type of method:

other: Adsorption was measured using a liquid scintillation counter

Media:

sediment

Specific details on test material used for the study:

- Uniform alkyl-labeled 14 C-DSDMAC was synthesized in our laboratories with a specific activity of 3 .2 μCi/mg (1.9 mCi/mmol). Radiochemical purity was >95%, as determined by TLC and HPLC.

Radiolabelling:

yes

Test temperature:

No details given

Details on study design: HPLC method:

Not relevant

Analytical monitoring:

yes

Details on sampling:

No details supplied

Details on matrix:

Collected from two rivers (Rapid creek, Rapid City, SD; Ohio River, Cincinnati, OH) at locations 0.5 to 1.0 mile below the discharge of municipal wastewater treatment treatment plants. The sites varied significantly in terms of hydrological/geological characteristics. Rapid creek is a slow-flowing mountain stream (mean discharge ~ 50 ft3/s) with a low wastewater dilution factor (~1:5-1:10), whereas the Ohio River is a rapidly flowing major river (mean discharge ~2000,000 ft3) with high wastewater dilution factor (>1:10,000). Sediment samples were analysed for cation exchange capacity (CEC), pH, particle distribution, organic carbon, and suspended solids levels by standard procedures. They were tested on a dry weight basis. Compartive data for the two river sediments and a standard EPA sediment (EPA 18) are given in Table 1.

Details on test conditions:

Mixtures of test chemical and sediment were placed into 220 ml beakers containing 150-200 ml of 0.01 M KCl buffer. the beakers were agitated on a rotary platform shaker at room temperature to maintain uniform solids suspensions and at various intervals aliquots were removed and centrifuged at 39,000 xg for 30 min to remove particulate matter. The amount of radioactivity in solution, or on the solids after combustion, was then quantitated by liquid scintillation counting (LSC)
and expressed as Kd, the solid/solution partition coefficient, as follows:

Kd = Csolids/Csolution -------- Eq (1)

Where:
Csolids = ug/g on the solids
Csolution = ug/mL in solution

Eq (1) is a modified form of the Freundlich isotherm:
Csolids = Kd x Csolution x 1/n ----------------- Eq (2)

which is generally used to model adsorption processes. The Kd value can be derived from equation (2) when n = 1 and can be extrapolated to different sediments by normalizing for the organic carbon content of the sediment.

Computational methods:

Csolids

C solids
K2 = ____________
C solution

where: Csolids = ug/g on the solids

Csolution = ug/ml in solution

Equation (1) is a modified form of the Freundlich isotherm

Csolids = KdCsolution l/n

which is generally used to model adsorption processes. the Kd value can be derived from equation 2 when n=1 and can be extrapolated to different sediments by normalising for the organic carbon content of the sediment.

Key result

Phase system:

other: Kd (sediment-water)

Type:

other: Kd (sediment-water)

Value:

12 489 L/kg

Remarks on result:

other: EPA 18 sediment

Key result

Phase system:

other: Kd (sediment-water)

Type:

other: Kd (sediment-water)

Value:

3 833 L/kg

Remarks on result:

other: Ohio river sediment

Key result

Phase system:

other: Kd (sediment-water)

Type:

other: Kd (sediment-water)

Value:

10 775 L/kg

Remarks on result:

other: Rapid creek sediment

Recovery of test material:

N

Transformation products:

not specified

Statistics:

No details given

Validity criteria fulfilled:

not specified

Conclusions:

Under the conditions of the study, the Kd values for the three sediments were determined to be 3833 (Ohio river), 10775 (Rapid creek) and 12489 (EPA 18) L/kg, indicating high adsorption potential or low mobility.

Executive summary:

A study was conducted to determine the sorption potential of the 14C-radiolabeled test substance, C18 DAQ (>95% active) in standard EPA sediment (EPA 18) and two river sediments from Rapid creek and Ohio river. Mixtures of test substance and sediment were placed into 220 mL beakers containing 150-200 mL of 0.01 M KCl buffer. The beakers were agitated on a rotary platform shaker at room temperature to maintain uniform solids suspensions and at various intervals aliquots were removed and centrifuged at 39,000 xg for 30 min to remove particulate matter. The amount of radioactivity in solution, or on the solids after combustion, was then quantitated by liquid scintillation counting (LSC). The Kd values for the three sediments were determined to be 3833 (Ohio river), 10775 (Rapid creek) and 12489 (EPA 18) L/kg (see below table):

Sediment	% Organic carbon	% Sand	% Clay	% Silt	CEC (meg/100g)	pH	Kd (L/kg)
EPA18	0.7	34.6	39.5	25.8	15.4	7.8	12489
Ohio river	2.0	28.0	39.7	32.4	18.4	--	3833
Rapid Creek	3.5	0.2	2.4	97.4	15.7	7.1	10775

 

Under the conditions, of the study, the test substance is considered to have high adsorption potential to sediment and soil (Larson and Vashon, 1983).

Description of key information

Based on the results of the read across studies, the test substance is expected to have little or no potential for mobility in soil.

Key value for chemical safety assessment

Koc at 20 °C:

562 314

Additional information

No soil adsorption study could be located on C12-18 DAQ. Therefore, read across studies available with the structurally similar substances DDAC and C18 DAQ are presented. Both the test and read across substances are di-alkyl dimethyl ammonium chloride compounds. While DDAC is structurally the same but only differs in having a slightly lower average alkyl chain length, the C16-18 DAQ contains higher average alkyl chains. Data from both substances together is expected to adequately cover the endpoint. 

Study 1:A study was conducted to determine the adsorption / desorption of the read across substance, DDAC (40.37% active) using the batch equilibrium, according to OECD Guideline 106, in compliance with GLP. 

The amount adsorbed on soils was calculated from depletion of the test substance in the overlaying solution (indirect method). The soils used were EURO-soil standard numbers 1, 2, 3, 4 and 5. The soil/solution ratio was 1:50 (1.0 g soil and 50 mL solution). Based on the results of preliminary tests, 100, 500, 1000, 5000 and 10000 mg/L were selected as nominal concentrations. The concentration of test substance in solution was determined via spectrophotometry. The concentration adsorbed to the soil was then determined by calculation. Under the study conditions, the test substance can be considered as immobile in five soil types. The adsorption mobility (Kaoc) and desorption mobility (Kdoc) coefficients were in the range 40339 to 280547 L/kg and 53883 to 232426 L/kg respectively. Based on the Kd values and organic carbon percentage, the respective Koc values were determined as follows:  

 

Soil type	% Organic carbon	CEC (mval/100g)	Adsorption			Desorption
			Ka (L/kg)	1/na	KaOC (L/kg)	Kd (L/kg)	1/nd	KdOC (L/kg)	Ka/Kd
Euro soil 1: clay	3.29	32.4	9230	0.4447	280547	3718	0.8048	113009	2.48
Euro soil 2: silt loam	28.9	28.9	2868	0.5715	120000	4237	0.7288	177280	0.68
Euro soil 3: loam	16.6	16.6	1456	0.4739	43855	2117	0.6390	63765	0.69
Euro soil 4: silt	17.3	17.3	2188	0.6248	160882	3161	0.6386	232426	0.69
5: loamy sand	24.1	24.1	1787	0.4582	40339	2387	0.5815	53883	0.75

Ka = Adsorption coefficient; Kaoc = Adsorption coefficient based on organic carbon content; Kd=Desorption coefficient; Kdoc = Desorption coefficient based on organic carbon content; Ka/Kd = Adsorption / Desorption distribution coefficient 

The 1/n values indicate that a non-linear relationship exists between the concentrations in soil and the concentrations the water. DDAC adsorbs strongly onto soil and does not desorb very easily for all soil types (2-3%). It is well known that, because of their positive charge, cationic surfactants adsorb strongly to the negatively charged surfaces of sludge, soil and sediments. Based on these results, it can be concluded that the substance is immobile in soil (Geffke, 2002). The average Koc was determined to be 129125 L/kg. 

Further, the DDAC biocides assessment report for Product Type 8 conducted under Directive 98/8/EC (evaluating Competent Authority: Italy, June 2015, attached in Section 13 of the IUCLID dataset), presented an additional study on DDAC, apart from the above EQC study (Geffke, 2002). In this study, DDAC was found to be immobile in in four soil/sediment types with the adsorption (Ka) and mobility (Kaoc) coefficients of

Ka=1095 L/kg and Kaoc=437805 L/kg for sand, Ka=8179 L/kg and Kaoc=908757 L/kg for sandy loam, Ka=32791 L/kg and Kaoc=1599564 L/kg for silty clay loam, and Ka=30851 L/kg and Kaoc=1469081 L/kg for silt loam. The desorption (Kd) and mobility (Kdoc) coefficients are following reported: Kd=591 L/kg and Kdoc=236473 L/kg for sand, Kd=2074 L/kg and Kdoc=230498 L/kg for sandy loam, Kd=8309 L/kg and Kdoc=405328 L/kg for silty clay loam, and Kd=7714 L/kg and Kdoc=367334 L/kg for silt loam. The average Koc is 1103801 L/kg.   

The RMS further stated that:“Based on the conclusion of the Ad-hoc follow up on ATMAC/TMAC (PT 8) (opinion of the ENV WG on the Koc to be used for the risk assessment) the koc value to be used for risk assessment is the mean Koc from the both studies available. The Koc value is 562314 L/Kg.” 

Study 2:A study was conducted to determine the sorption potential of the 14C-radiolabeled read across substance, C18 DAQ (>95% active) in standard EPA sediment (EPA 18) and two river sediments from Rapid creek and Ohio river. Mixtures of test substance and sediment were placed into 220 mL beakers containing 150-200 mL of 0.01 M KCl buffer. The beakers were agitated on a rotary platform shaker at room temperature to maintain uniform solids suspensions and at various intervals aliquots were removed and centrifuged at 39,000 xg for 30 min to remove particulate matter. The amount of radioactivity in solution, or on the solids after combustion, was then quantitated by liquid scintillation counting (LSC). The Kd values for the three sediments were determined to be 3833 (Ohio river), 10775 (Rapid creek) and 12489 (EPA 18) L/kg (see below table): 

 

Sediment	% Organic carbon	% Sand	% Clay	% Silt	CEC (meg/100g)	pH	Kd (L/kg)
EPA18	0.7	34.6	39.5	25.8	15.4	7.8	12489
Ohio river	2.0	28.0	39.7	32.4	18.4	--	3833
Rapid Creek	3.5	0.2	2.4	97.4	15.7	7.1	10775

 

Under the conditions, of the study, the test substance is considered to have high adsorption potential to sediment and soil (Larson and Vashon, 1983). 

 

For the EU Risk assessment, a Kd sediment of 10000 L/kg was assumed for the sediment/water partitioning of C18 DAQ/DODMAC. When assuming a suspended matter concentration of 15 mg/L in an STP effluent a Kd susp. matter of 16800 L/kg can be calculated from these data. As no measured data for the adsorption to soil is available the Kd sediment was used for Kd soil in the EU RAR.  

In general, for quaternary ammonium compounds there is no relationship between the values of Kd and the OC-content of the soils. This confirms that organic carbon content alone is not a suitable normalization basis for charged organic substances (Droge & Goss 2013). When comparing the sorption data per soil, no consistent variation of the Kd–values with the different soils can be discerned. Nevertheless, in line with the biocides assessment report, the higher mean Koc value of 562314 L/kg, which was derived based on both the available studies on the read across substance DDAC for all soil types, has as a worst case been considered further for hazard/risk assessment.