Benzododecinium chloride

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:

From March 10, 1987 to September 25, 1987

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: U.S. EPA Guideline subdivision N 163-1

Deviations:

no

GLP compliance:

yes

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

25±1°C

Analytical monitoring:

yes

Details on sampling:

- Isotopic dilutions:
To ensure availability of enough test substance, 20 mL of the purified primary stock solution of the radiolabelled test substance (46 µg/mL in methanol) were placed into a 50 mL volumetric flask. The solvent was evaporated under nitrogen. 30 mL of non-radiolabelled test substance (1000 µg/mL in H2O) were added and brought to 50 mL total volume with water. The concentration of the isotopically diluted purified stock solution was 698 µg/mL (purity: 99.1% as per TLC-radiochemical determination). Five 50 uL replicates of this solution were assayed by LSC to calculate the specific activity. The specific activity was calculated to be 2.03E04 dpm/µg.

Details on matrix:

Test soil:
- Source: The #32 sand, #45 silt loam, #59 sandy loam and #58 clay loam were supplied by ABC laboratories. Representative subsamples of these soils were collected and shipped to A and L Mid west agricultural laboratories Inc, Omaha, Nebraska for characterisation.
- The soils were sieved through a 10 mesh screen and autoclaved at 20 degF (121 degC) and 15 psi for 1 h.

Properties:
- Soil texture:
- % sand: 93, 38, 64 and 28 for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively
- % silt: 3, 52, 20 and 38 for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively
- % clay: 4, 10, 16 and 34 for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively
- Organic carbon (%): 0.2, 1, 1.6 and 3.9 for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively
- CEC (meq/100 g): 3.8, 7.6, 9.5 and 20.9 meq/100 g for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively
- pH: 6.5, 7.7, 6.2 and 7.5 for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively
- Bulk density (g/cm3): 1.56, 1.45, 1.18 and 1.03 for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively
- Field capacity at 1/3 Bar: 7.77, 17.36, 15.12 for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively

Details on test conditions:

Preliminary study:
The objectives of the preliminary study were to select appropriate soil to water ratios and equilibrium times for the test compound and four soil types at a nominal test concentration of 1 µg/mL. The test containers were Pyrex culture tubes.
- At the 1:20 soil to water ratio, greater than 95% of the test substance was adsorbed to the soil (#32 sand, #45 silt loam, #59 sandy loam and #58 clay loam). Significant 14C-losses were attributed to adsorption of the test substance to the Pyrex test containers and to filters which were employed for filtration of supernatants.
- Additionally the preliminary study identified 4 experimental limitations. They were: (a) elimination of any filtration steps due to loss of the 14C-test substance onto filter media (b) use of direct addition of 14C-test substance onto the test systems to reduce 14C-losses incurred by manipulation of 0.01 M CaCl2 14C-test substance stock solutions (c) use of nalgene test containers rather than silanized glass to reduce adsorption of 14C- test substance to the test system surfaces (D) use of an increased water to soil ratio to decrease the percent 14C-test substance adsorbed to soil.
- The highest practical water to soil ratio that could be used was 200:1 since the size of the test container could not exceed a capacity which could be successfully centrifuged (1.e., 250 mL capacity).

Main study:
A: ADSORPTION PROCEDURE:
- Ten one-gram portions of each soil were weighed and transferred into appropriately labelled Nalgene bottles. To each bottle, 200 mL aliquots of 0.01 M CaCl2 solution were added.
- Nominal test concentrations of 0, 0.1, 0.5, 1 and 2 µg/mL (i.e., equivalent to a measured concentration of 0.689, 0.441, 0.887 and 1.85 µg/mL) were prepared by pipetting appropriate aliquots of isotopically diluted purified primary stock solution of 14C-test substance at 698 µg/mL directly into nalgene test bottles containing 0.01 M CaCl2 solution and test soils. The 0.1, 0.5, 1 and 2 µg/mL nominal test concentrations received approximately 28 µL, 243 µL, 287 µL and 573 µL respectively.
- Equal volumes of test substance isotopically diluted purified primary stock solution were added directly into nalgene test bottles containing only 0.01M CaCl2 solution.
- Duplicate LSC samples were taken of each resulting 14C-test substance concentration (less soil) to measure the levels of the 14C-test substance present at initiation.
- The soil suspensions were shaken in darkness for 20 h on a mechanical shaker in an environmentally controlled chamber at 25±1°C. The suspensions were then centrifuged for 15 mins at approximately. 2000 rpm in centrifuge. Duplicate 5 mL aliquots of the supernatant were taken for liquid scintillation counting analysis directly from each nalgene test bottle. The remaining supernatant (approximately 186 mL) was removed from each bottle by decanting.

B. DESORPTION PROCEDURE:
- 196 mL aliquots of sterile test water at a 0.01 M CaCl2 concentration were added to each sample. All soil suspensions were shaken in darkness on a mechanical shaker for 14 h and 45 min in an environmentally controlled chamber at 25±1°C.
- All soil suspensions were shaken in darkness on a mechanical shaken for 14 h and 45 min in an environmentally controlled chamber at 25±1°C.
- After shaking, the suspensions were centrifuged for 15 mins at approximately 2000 rpm in a centrifuge. Duplicate 10 mL aliquots of the supernatant were taken for liquid scintillation counting analysis directly from the nalgene sample bottles. The remaining supernatant was removed by pipetting. The soil was air dried, combusted in triplicate, and was then analyzed by liquid scintillation counting to determine the 14C-mass balance.
- Following the initial liquid scintillation counting analysis of these combusted soil samples, triplicate re-combustions were done on those samples that were determined to be "questionable".
- Questionable results included: 14C-residue levels at 14C-accountability <80% or >120% and at 14C-residue replicate levels having a high variability.

Duration:

20 h

Initial conc. measured:

0.689 other: µg/mL

Duration:

20 h

Initial conc. measured:

0.441 other: µg/mL

Duration:

20 h

Initial conc. measured:

0.887 other: µg/mL

Duration:

20 h

Initial conc. measured:

1.85 other: µg/mL

Computational methods:

Measurements of radioactivity were made using a Beckman liquid scintillation system, model 3801 for 5 minutes or to a 2 sigma value of 2.0. The beckman LSC system determines total counts and the results are reported in disintegrations per minute (DPM or ppm).

for
the definitive test samples were counted where the LSC system was interfaced with a Beckman data transporter. Data calculations were performed using an IBMR PC-XTR system.

Liquid sample aliquots were pipetted into scintillation vials where they received appropriate aliquots of beckman ready-SolvTM MP for LSC analysis.
Soilsamples for LSc analysis were combusted in a Packard 306D tri-carb sample oxidizer to determine 14C-mass balance.

Calculations:
The adsorption and desorption properties of the test substance were characterized by Freundlich isotherm:
x/m = Kd.Ce(1/n) 1n x/m = 1n Kd + 1/n 1n Ce
where,
X= the amount of chemical adsorbed in µg
M= mass of adsorbent in g.
When in equilibrium with an aqueous solution solution, where
Ce= concentration of chemical in aqueous solution
Kd= adsorption coefficient and
N= a constant

The Freundlich isotherm given as 1n x/m = 1n Kd + 1/n 1n Ce is the form of a line equation. When 1n Ce is plotted vs 1n x/m, the constants Kd and n are determined from the slope (1/n) and intercept (1n Kd) of the resultant straight line.

The equilibrium concentration of the test compound (Ce) in the aqueous phase of the samples was determined by LSC analysis.
The amount of test compound in µg adsorbed, X, in each of the samples was calculated in the following manner,
Xad= [(µg/mL of test compound in solution at initiation (In) x (volume added at initiation)] – [(µg/mL of test compound in equilibrium after adsorption phase (ad) x (volume added at initiation)]

Desorption phase:
Xde= [(µg/mL of test compound in solution at initiation (In) x (volume added at initiation)] – [(µg/mL of test compound in equilibrium at adsorption phase (ad) x (volume of filterate removed at adsorption phase)]- [(µg/mL in solution at desorption phase (de)) x (volume added at initiation)]

The mass of soil, m, for each sample was the dry soil weight (1.000 g).

Calculations were made of x/m, 1n x/m and 1n Ce. From this data, 1n Ce was plotted vs 1n x/m and line equations for the adsorption isotherm and desorption isotherm for each of the four soil types were determined.

The constants Kd and n were determined for each soil type from the slope (1/n) and y intercept (1n Kd) of the corresponding line equation. The adsorption coefficient Koc for each soil sample was determined by using the equation Koc = (Kd x 100% O.C.) where % O.C. is the organic carbon content of the soil. Percent organic values received from agricultural labs were converted to % organic carbon by the equation % O.C. = (% O.M.)/2.0.)

The 14C-mass balance of test substance in each soil system was determined. The µg in soil after desorption was determined by combustion radioanalysis using the following formula:
µg in soil=
DPM/ S.A. (sample size g) x 1.0. g x % recovery from soil

Key result

Type:

Koc

Remarks:

mobility coefficient

Value:

6 171 657 L/kg

Temp.:

25 °C

Matrix:

#32 sand

% Org. carbon:

0.1

Remarks on result:

other: immobile

Key result

Type:

other: Ka

Remarks:

adsorption coefficient

Value:

6 172 L/kg

Temp.:

25 °C

Matrix:

#32 sand

% Org. carbon:

0.1

Remarks on result:

other: immobile

Key result

Type:

Koc

Remarks:

mobility coefficient

Value:

2 159 346 L/kg

Temp.:

25 °C

Matrix:

#45 silt loam

% Org. carbon:

0.5

Remarks on result:

other: immobile

Key result

Type:

other: Ka

Remarks:

adsorption coefficient

Value:

10 797 L/kg

Temp.:

25 °C

Matrix:

#45 silt loam

% Org. carbon:

0.5

Remarks on result:

other: immobile

Key result

Type:

Koc

Remarks:

mobility coefficient

Value:

640 389 L/kg

Temp.:

25 °C

Matrix:

#59 sandy loam

% Org. carbon:

0.8

Remarks on result:

other: immobile

Key result

Type:

other: Ka

Remarks:

adsorption coefficient

Value:

5 123 L/kg

Temp.:

25 °C

Matrix:

#59 sandy loam

% Org. carbon:

0.8

Remarks on result:

other: immobile

Key result

Type:

Koc

Remarks:

mobility coefficient

Value:

1 663 039 L/kg

Temp.:

25 °C

Matrix:

#58 clay loam

% Org. carbon:

2

Remarks on result:

other: immobile

Key result

Type:

other: Ka

Remarks:

adsorption coefficient

Value:

32 429 L/kg

Temp.:

25 °C

Matrix:

#58 clay loam

% Org. carbon:

2

Remarks on result:

other: immobile

Details on results (HPLC method):

The #32 sand at 0.1% organic carbon had an adsorption Kd and Koc as: 6,172 and 6,171,657 respectively and a desorption Kd and Koc as: 7,137 and 7,137,310 respectively.
The #45 silt loam at 0.5% organic carbon had an adsorption Kd and Koc as: 10,797 and 2,159,346 respectively and a desorption Kd and Koc as: 14,083 and 2,816.590 respectively.
The #59 sandy loam at 0.8% organic carbon had an adsorption Kd and Koc as: 5,123 and 640,389 respectively and a desorption Kd and Koc as: 96,540 and 12,067,457 respectively.
The #58 clay loam at 2% organic carbon had an adsorption Kd and Koc as: 32,429 and 1,663,039 respectively and a desorption Kd and Koc as: 165,556 and 8,490,062 respectively.

Transformation products:

no

Details on results (Batch equilibrium method):

See the below table under 'any other information on results incl. tables' for percent adsorption and desorption and total mass balance.

Table 1. Adsorption (K_d) and mobility coefficients.(K_oc)

Soil Types	Adsorption coefficient (Kd)	Mobility coefficient (Koc)	Desorption coefficient (Kd)	Mobility coefficient (Koc)
# 32 Sand	6,172	6,171,657	7173	7137310
# 45 Silt loam	10,797	2,159,346	14083	2816590
# 58 Clay loam	32,429	1,663,039	165556	8490062
# 59 Sandyloam	5,123	640,389	96540	12067457

Table 2. Mean percentage of adsorption, desorption and total mass balance

Soil type	Mean percent adsorption	Mean percent desorption	Mean percent total mass balance
# 32 sand	97.91±0.72%	1.19±0.48%	100.04±15.20%
# 45 silt loam	98.67±0.16%	0.45±0.17%	103.29±10.69%
# 59 sandy loam	98.51±0.77%	0.23±0.05%	95.29±4.94%
# 58 clay loam	99.13±0.10%	0.09±0.02%	100.04±10.97%

 No apparent degradation occurred to the test substance in any of the four soils under the conditions of the study.

Validity criteria fulfilled:

not specified

Conclusions:

Under the conditions of the study, the test substance was considered to have little or no potential for mobility in all the four soil/sediment types, with a mean Koc value was 2,658,608 L/kg.

Executive summary:

A study was conducted to determine the adsorption / desorption of the test substance, C12-16 ADBAC (30% active in water and 98.4% radiolabeled purity), according to U.S. EPA Guideline subdivision N 163-1, in compliance with GLP. The adsorption / desorption coefficients were determined by equilibrating with four soil types (sand, sandy loam, clay loam and silt loam). Based on the very high percent of 14C-test substance adsorption onto the test soil in a preliminary study conducted with a 1: 20 soil: water ratio, the definitive study was carried out at 1: 200 soil: water. Nominal test concentrations of 0, 0.1, 0.5, 1 and 2 µg/mL (equivalent to measured concentrations of 0.689, 0.441, 0.887 and 1.85 µg/mL) were prepared by pipetting appropriate aliquots of 14C-test substance at 698 µg/mL directly into bottles containing 0.01 M CaCl2 solution and soils. Liquid scintillation counting was employed to measure the concentrations in the aqueous phase. The amount of the test substance remaining adsorbed on the soil was determined by combustion/radio analysis. Although the amount of 14C-test substance adsorbed onto the four test soils was well above the 20 to 80% recommended to ensure Freundlich isotherms, excellent correlations were obtained ranging from 0.9682 to 0.9983. In addition, the 14C-mass balance for the four soils types ranged from 95.3 to 103.2%. No apparent degradation of the test substance occurred in any of the four soils. The Freundlich constants were determined as summarized below:

Soil Types	% organic carbon	Adsorption coefficient (Kd)	Mobility coefficient (Koc)	Desorption coefficient (Kd)	Mobility coefficient (Koc)
Sand	0.1	6,172	6,171,657	7173	7137310
Silt loam	0.5	10,797	2,159,346	14083	2816590
Clay loam	2.0	32,429	1,663,039	165556	8490062
Sandy loam	0.8	5,123	640,389	96540	12067457

 

The mean Koc value was 2,658,608 L/kg. Under the conditions of the study, the test substance was considered to have little or no potential for mobility in all the four soil/sediment types and therefore should not pose a probable environmental risk for contamination of ground water (Daly, 1988).

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:

From March 10, 1987 to September 25, 1987

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

KL2 due to RA

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:

other: U.S. EPA Guideline subdivision N 163-1

Deviations:

no

GLP compliance:

yes

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

25±1°C

Analytical monitoring:

yes

Details on sampling:

- Isotopic dilutions:
To ensure availability of enough test substance, 20 mL of the purified primary stock solution of the radiolabelled test substance (46 µg/mL in methanol) were placed into a 50 mL volumetric flask. The solvent was evaporated under nitrogen. 30 mL of non-radiolabelled test substance (1000 µg/mL in H2O) were added and brought to 50 mL total volume with water. The concentration of the isotopically diluted purified stock solution was 698 µg/mL (purity: 99.1% as per TLC-radiochemical determination). Five 50 uL replicates of this solution were assayed by LSC to calculate the specific activity. The specific activity was calculated to be 2.03E04 dpm/µg.

Details on matrix:

Test soil:
- Source: The #32 sand, #45 silt loam, #59 sandy loam and #58 clay loam were supplied by ABC laboratories. Representative subsamples of these soils were collected and shipped to A and L Mid west agricultural laboratories Inc, Omaha, Nebraska for characterisation.
- The soils were sieved through a 10 mesh screen and autoclaved at 20 degF (121 degC) and 15 psi for 1 h.

Properties:
- Soil texture:
- % sand: 93, 38, 64 and 28 for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively
- % silt: 3, 52, 20 and 38 for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively
- % clay: 4, 10, 16 and 34 for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively
- Organic carbon (%): 0.2, 1, 1.6 and 3.9 for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively
- CEC (meq/100 g): 3.8, 7.6, 9.5 and 20.9 meq/100 g for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively
- pH: 6.5, 7.7, 6.2 and 7.5 for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively
- Bulk density (g/cm3): 1.56, 1.45, 1.18 and 1.03 for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively
- Field capacity at 1/3 Bar: 7.77, 17.36, 15.12 for # 32 sand, #45 silt loam, #59 sandy loam and #58 clay loam respectively

Details on test conditions:

Preliminary study:
The objectives of the preliminary study were to select appropriate soil to water ratios and equilibrium times for the test compound and four soil types at a nominal test concentration of 1 µg/mL. The test containers were Pyrex culture tubes.
- At the 1:20 soil to water ratio, greater than 95% of the test substance was adsorbed to the soil (#32 sand, #45 silt loam, #59 sandy loam and #58 clay loam). Significant 14C-losses were attributed to adsorption of the test substance to the Pyrex test containers and to filters which were employed for filtration of supernatants.
- Additionally the preliminary study identified 4 experimental limitations. They were: (a) elimination of any filtration steps due to loss of the 14C-test substance onto filter media (b) use of direct addition of 14C-test substance onto the test systems to reduce 14C-losses incurred by manipulation of 0.01 M CaCl2 14C-test substance stock solutions (c) use of nalgene test containers rather than silanized glass to reduce adsorption of 14C- test substance to the test system surfaces (D) use of an increased water to soil ratio to decrease the percent 14C-test substance adsorbed to soil.
- The highest practical water to soil ratio that could be used was 200:1 since the size of the test container could not exceed a capacity which could be successfully centrifuged (1.e., 250 mL capacity).

Main study:
A: ADSORPTION PROCEDURE:
- Ten one-gram portions of each soil were weighed and transferred into appropriately labelled Nalgene bottles. To each bottle, 200 mL aliquots of 0.01 M CaCl2 solution were added.
- Nominal test concentrations of 0, 0.1, 0.5, 1 and 2 µg/mL (i.e., equivalent to a measured concentration of 0.689, 0.441, 0.887 and 1.85 µg/mL) were prepared by pipetting appropriate aliquots of isotopically diluted purified primary stock solution of 14C-test substance at 698 µg/mL directly into nalgene test bottles containing 0.01 M CaCl2 solution and test soils. The 0.1, 0.5, 1 and 2 µg/mL nominal test concentrations received approximately 28 µL, 243 µL, 287 µL and 573 µL respectively.
- Equal volumes of test substance isotopically diluted purified primary stock solution were added directly into nalgene test bottles containing only 0.01M CaCl2 solution.
- Duplicate LSC samples were taken of each resulting 14C-test substance concentration (less soil) to measure the levels of the 14C-test substance present at initiation.
- The soil suspensions were shaken in darkness for 20 h on a mechanical shaker in an environmentally controlled chamber at 25±1°C. The suspensions were then centrifuged for 15 mins at approximately. 2000 rpm in centrifuge. Duplicate 5 mL aliquots of the supernatant were taken for liquid scintillation counting analysis directly from each nalgene test bottle. The remaining supernatant (approximately 186 mL) was removed from each bottle by decanting.

B. DESORPTION PROCEDURE:
- 196 mL aliquots of sterile test water at a 0.01 M CaCl2 concentration were added to each sample. All soil suspensions were shaken in darkness on a mechanical shaker for 14 h and 45 min in an environmentally controlled chamber at 25±1°C.
- All soil suspensions were shaken in darkness on a mechanical shaken for 14 h and 45 min in an environmentally controlled chamber at 25±1°C.
- After shaking, the suspensions were centrifuged for 15 mins at approximately 2000 rpm in a centrifuge. Duplicate 10 mL aliquots of the supernatant were taken for liquid scintillation counting analysis directly from the nalgene sample bottles. The remaining supernatant was removed by pipetting. The soil was air dried, combusted in triplicate, and was then analyzed by liquid scintillation counting to determine the 14C-mass balance.
- Following the initial liquid scintillation counting analysis of these combusted soil samples, triplicate re-combustions were done on those samples that were determined to be "questionable".
- Questionable results included: 14C-residue levels at 14C-accountability <80% or >120% and at 14C-residue replicate levels having a high variability.

Duration:

20 h

Initial conc. measured:

0.689 other: µg/mL

Duration:

20 h

Initial conc. measured:

0.441 other: µg/mL

Duration:

20 h

Initial conc. measured:

0.887 other: µg/mL

Duration:

20 h

Initial conc. measured:

1.85 other: µg/mL

Computational methods:

Measurements of radioactivity were made using a Beckman liquid scintillation system, model 3801 for 5 minutes or to a 2 sigma value of 2.0. The beckman LSC system determines total counts and the results are reported in disintegrations per minute (DPM or ppm).

for
the definitive test samples were counted where the LSC system was interfaced with a Beckman data transporter. Data calculations were performed using an IBMR PC-XTR system.

Liquid sample aliquots were pipetted into scintillation vials where they received appropriate aliquots of beckman ready-SolvTM MP for LSC analysis.
Soilsamples for LSc analysis were combusted in a Packard 306D tri-carb sample oxidizer to determine 14C-mass balance.

Calculations:
The adsorption and desorption properties of the test substance were characterized by Freundlich isotherm:
x/m = Kd.Ce(1/n) 1n x/m = 1n Kd + 1/n 1n Ce
where,
X= the amount of chemical adsorbed in µg
M= mass of adsorbent in g.
When in equilibrium with an aqueous solution solution, where
Ce= concentration of chemical in aqueous solution
Kd= adsorption coefficient and
N= a constant

The Freundlich isotherm given as 1n x/m = 1n Kd + 1/n 1n Ce is the form of a line equation. When 1n Ce is plotted vs 1n x/m, the constants Kd and n are determined from the slope (1/n) and intercept (1n Kd) of the resultant straight line.

The equilibrium concentration of the test compound (Ce) in the aqueous phase of the samples was determined by LSC analysis.
The amount of test compound in µg adsorbed, X, in each of the samples was calculated in the following manner,
Xad= [(µg/mL of test compound in solution at initiation (In) x (volume added at initiation)] – [(µg/mL of test compound in equilibrium after adsorption phase (ad) x (volume added at initiation)]

Desorption phase:
Xde= [(µg/mL of test compound in solution at initiation (In) x (volume added at initiation)] – [(µg/mL of test compound in equilibrium at adsorption phase (ad) x (volume of filterate removed at adsorption phase)]- [(µg/mL in solution at desorption phase (de)) x (volume added at initiation)]

The mass of soil, m, for each sample was the dry soil weight (1.000 g).

Calculations were made of x/m, 1n x/m and 1n Ce. From this data, 1n Ce was plotted vs 1n x/m and line equations for the adsorption isotherm and desorption isotherm for each of the four soil types were determined.

The constants Kd and n were determined for each soil type from the slope (1/n) and y intercept (1n Kd) of the corresponding line equation. The adsorption coefficient Koc for each soil sample was determined by using the equation Koc = (Kd x 100% O.C.) where % O.C. is the organic carbon content of the soil. Percent organic values received from agricultural labs were converted to % organic carbon by the equation % O.C. = (% O.M.)/2.0.)

The 14C-mass balance of test substance in each soil system was determined. The µg in soil after desorption was determined by combustion radioanalysis using the following formula:
µg in soil=
DPM/ S.A. (sample size g) x 1.0. g x % recovery from soil

Key result

Type:

Koc

Remarks:

mobility coefficient

Value:

6 171 657 L/kg

Temp.:

25 °C

Matrix:

#32 sand

% Org. carbon:

0.1

Remarks on result:

other: immobile

Key result

Type:

other: Ka

Remarks:

adsorption coefficient

Value:

6 172 L/kg

Temp.:

25 °C

Matrix:

#32 sand

% Org. carbon:

0.1

Remarks on result:

other: immobile

Key result

Type:

Koc

Remarks:

mobility coefficient

Value:

2 159 346 L/kg

Temp.:

25 °C

Matrix:

#45 silt loam

% Org. carbon:

0.5

Remarks on result:

other: immobile

Key result

Type:

other: Ka

Remarks:

adsorption coefficient

Value:

10 797 L/kg

Temp.:

25 °C

Matrix:

#45 silt loam

% Org. carbon:

0.5

Remarks on result:

other: immobile

Key result

Type:

Koc

Remarks:

mobility coefficient

Value:

640 389 L/kg

Temp.:

25 °C

Matrix:

#59 sandy loam

% Org. carbon:

0.8

Remarks on result:

other: immobile

Key result

Type:

other: Ka

Remarks:

adsorption coefficient

Value:

5 123 L/kg

Temp.:

25 °C

Matrix:

#59 sandy loam

% Org. carbon:

0.8

Remarks on result:

other: immobile

Key result

Type:

Koc

Remarks:

mobility coefficient

Value:

1 663 039 L/kg

Temp.:

25 °C

Matrix:

#58 clay loam

% Org. carbon:

2

Remarks on result:

other: immobile

Key result

Type:

other: Ka

Remarks:

adsorption coefficient

Value:

32 429 L/kg

Temp.:

25 °C

Matrix:

#58 clay loam

% Org. carbon:

2

Remarks on result:

other: immobile

Details on results (HPLC method):

The #32 sand at 0.1% organic carbon had an adsorption Kd and Koc as: 6,172 and 6,171,657 respectively and a desorption Kd and Koc as: 7,137 and 7,137,310 respectively.
The #45 silt loam at 0.5% organic carbon had an adsorption Kd and Koc as: 10,797 and 2,159,346 respectively and a desorption Kd and Koc as: 14,083 and 2,816.590 respectively.
The #59 sandy loam at 0.8% organic carbon had an adsorption Kd and Koc as: 5,123 and 640,389 respectively and a desorption Kd and Koc as: 96,540 and 12,067,457 respectively.
The #58 clay loam at 2% organic carbon had an adsorption Kd and Koc as: 32,429 and 1,663,039 respectively and a desorption Kd and Koc as: 165,556 and 8,490,062 respectively.

Transformation products:

no

Details on results (Batch equilibrium method):

See the below table under 'any other information on results incl. tables' for percent adsorption and desorption and total mass balance.

Table 1. Adsorption (K_d) and mobility coefficients.(K_oc)

Soil Types	Adsorption coefficient (Kd)	Mobility coefficient (Koc)	Desorption coefficient (Kd)	Mobility coefficient (Koc)
# 32 Sand	6,172	6,171,657	7173	7137310
# 45 Silt loam	10,797	2,159,346	14083	2816590
# 58 Clay loam	32,429	1,663,039	165556	8490062
# 59 Sandyloam	5,123	640,389	96540	12067457

Table 2. Mean percentage of adsorption, desorption and total mass balance

Soil type	Mean percent adsorption	Mean percent desorption	Mean percent total mass balance
# 32 sand	97.91±0.72%	1.19±0.48%	100.04±15.20%
# 45 silt loam	98.67±0.16%	0.45±0.17%	103.29±10.69%
# 59 sandy loam	98.51±0.77%	0.23±0.05%	95.29±4.94%
# 58 clay loam	99.13±0.10%	0.09±0.02%	100.04±10.97%

 No apparent degradation occurred to the test substance in any of the four soils under the conditions of the study.

Validity criteria fulfilled:

not specified

Conclusions:

Based on the results of the read across study, the test substance is considered to have little or no potential for mobility in all the four soil/sediment types, with a mean Koc value was 2,658,608 L/kg.

Executive summary:

A study was conducted to determine the adsorption / desorption of the read across substance, C12-16 ADBAC (30% active and 98.4% radiolabeled purity), according to U.S. EPA Guideline subdivision N 163-1, in compliance with GLP. The adsorption / desorption coefficients were determined by equilibrating with four soil types (sand, sandy loam, clay loam and silt loam). Based on the very high percent of 14C-read across substance adsorption onto the test soil in a preliminary study conducted with a 1: 20 soil: water ratio, the definitive study was carried out at 1: 200 soil: water. Nominal test concentrations of 0, 0.1, 0.5, 1 and 2 µg/mL (equivalent to measured concentrations of 0.689, 0.441, 0.887 and 1.85 µg/mL) were prepared by pipetting appropriate aliquots of 14C-read across substance at 698 µg/mL directly into bottles containing 0.01 M CaCl2 solution and soils. Liquid scintillation counting was employed to measure the concentrations in the aqueous phase. The amount of the read across substance remaining adsorbed on the soil was determined by combustion/radio analysis. Although the amount of 14C-read across substance adsorbed onto the four test soils was well above the 20 to 80% recommended to ensure Freundlich isotherms, excellent correlations were obtained ranging from 0.9682 to 0.9983. In addition, the 14C-mass balance for the four soils types ranged from 95.3 to 103.2%. No apparent degradation of the read across substance occurred in any of the four soils. The Freundlich constants were determined as summarized below:

Soil Types	% organic carbon	Adsorption coefficient (Kd)	Mobility coefficient (Koc)	Desorption coefficient (Kd)	Mobility coefficient (Koc)
Sand	0.1	6,172	6,171,657	7173	7137310
Silt loam	0.5	10,797	2,159,346	14083	2816590
Clay loam	2.0	32,429	1,663,039	165556	8490062
Sandy loam	0.8	5,123	640,389	96540	12067457

 

The mean Koc value was 2,658,608 L/kg. Under the conditions of the study, the read across substance was considered to have little or no potential for mobility in all the four soil/sediment types and therefore should not pose a probable environmental risk for contamination of ground water (Daly, 1988). Based on the results of the read across study, a similar adsorption potential is expected for the test substance.

Description of key information

Based on the results of the read across study, the test substance, C12 ADBAC, can be considered to be immobile in soil with a mean Koc of 1640329 L/kg.

Key value for chemical safety assessment

Koc at 20 °C:

1 640 329

Additional information

A study was conducted to determine the adsorption / desorption of the read across substance, C12-16 ADBAC (30% active and 98.4% radiolabeled purity), according to U.S. EPA Guideline subdivision N 163-1, in compliance with GLP. The adsorption / desorption coefficients were determined by equilibrating with four soil types (sand, sandy loam, clay loam and silt loam). Based on the very high percent of 14C-read across substance adsorption onto the test soil in a preliminary study conducted with a 1: 20 soil: water ratio, the definitive study was carried out at 1: 200 soil: water. Nominal test concentrations of 0, 0.1, 0.5, 1 and 2 µg/mL (equivalent to measured concentrations of 0.689, 0.441, 0.887 and 1.85 µg/mL) were prepared by pipetting appropriate aliquots of 14C-read across substance at 698 µg/mL directly into bottles containing 0.01 M CaCl2 solution and soils. Liquid scintillation counting was employed to measure the concentrations in the aqueous phase. The amount of the read across substance remaining adsorbed on the soil was determined by combustion/radio analysis. Although the amount of 14C-read across substance adsorbed onto the four test soils was well above the 20 to 80% recommended to ensure Freundlich isotherms, excellent correlations were obtained ranging from 0.9682 to 0.9983. In addition, the 14C-mass balance for the four soils types ranged from 95.3 to 103.2%. No apparent degradation of the read across substance occurred in any of the four soils. The Freundlich constants were determined as summarized below:

 

Soil Types	% organic carbon	Adsorption coefficient (Kd)	Mobility coefficient (Koc)	Desorption coefficient (Kd)	Mobility coefficient (Koc)
Sand	0.1	6,172	6,171,657	7173	7137310
Silt loam	0.5	10,797	2,159,346	14083	2816590
Clay loam	2.0	32,429	1,663,039	165556	8490062
Sandy loam	0.8	5,123	640,389	96540	12067457

The mean Koc value was 2,658,608 L/kg. Under the conditions of the study, the read across substance was considered to have little or no potential for mobility in all the four soil/sediment types and therefore should not pose a probable environmental risk for contamination of ground water (Daly, 1988). Based on the results of the read across study, a similar adsorption potential is expected for the test substance.

Apart from the above study, the Biocides assessment report on C12-16 ADBAC reported similar results to be found in another soil adsorption study, conducted by the European Quats consortium, in three soil types. The desorption (Kd) and mobility (Kdoc) coefficients were reported to be: Kd = 2828 and Kdoc = 81971 for loam, Kd = 6795 and Kdoc = 73459 for loamy sand, Kd = 2778 and Kdoc = 1111200 for silt loam. The mean Koc was calculated to be 282,624.3 L/kg. Based on the results of these studies, C12-16 ADBAC was concluded to be immobile, which is well known fact because of the positive charge, which makes the cationic surfactants adsorb strongly to the negatively charged surfaces of sludge, soil and sediments. For the purpose of risk assessment, a mean Koc value of 1640329 L/Kg, based on both these studies were considered in the Biocides report (ECHA biocides assessment report, 2015). In line with the biocides dossier, and based on read across approach, the mean Koc value of 1640329 L/Kg has also been considered for the test substance, C12 ADBAC, which indicates low mobility.