Diarsenic trioxide

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Remarks:

adsorption

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

batch equilibration method.

GLP compliance:

not specified

Type of method:

batch equilibrium method

Media:

soil

Specific details on test material used for the study:

Na2HAsO4.7H2O

Radiolabelling:

no

Test temperature:

not reported

Analytical monitoring:

yes

Details on sampling:

Medium: AP hprizon
Background conc. of As: not reported
Location: USA
air-dried and sieved (2 mm)
sampling solution phase: shaking for 18h followed by filtration through quantitative filter paper

Matrix no.:

#1

Matrix type:

other: very fine, montmorillonitic acid, thermic vertic haplaquept

% Clay:

54.7

% Org. carbon:

1.54

pH:

4.8

CEC:

32.2 meq/100 g soil d.w.

Matrix no.:

#2

Matrix type:

other: Calciorthid

% Clay:

10.7

% Org. carbon:

0.44

pH:

8.5

CEC:

14.7 meq/100 g soil d.w.

Matrix no.:

#3

Matrix type:

other: clayey, kaolinitic, thermic typic hapludult

% Clay:

8.3

% Org. carbon:

0.61

pH:

5.7

CEC:

2 meq/100 g soil d.w.

Matrix no.:

#4

Matrix type:

other: medial, isothermic typic eithandept

% Clay:

0.9

% Org. carbon:

6.62

pH:

5.9

CEC:

22.5 meq/100 g soil d.w.

Matrix no.:

#5

Matrix type:

other: euic, thermic typic medisaprist

% Clay:

17.6

% Org. carbon:

11.6

pH:

3.9

CEC:

26.9 meq/100 g soil d.w.

Matrix no.:

#6

Matrix type:

other: clayey, kaolinitic, isohyperthermic typic torrox

% Clay:

28.2

% Org. carbon:

1.67

pH:

6

CEC:

11 meq/100 g soil d.w.

Matrix no.:

#7

Matrix type:

other: fine-silty mixed (calc.) thermic typic udifluvent

% Clay:

2.8

% Org. carbon:

0.21

pH:

6.9

CEC:

4.1 meq/100 g soil d.w.

Matrix no.:

#8

Matrix type:

other: fine-silty, mixed thermic awuic fragiudalf

% Clay:

6.2

% Org. carbon:

0.83

pH:

6.6

CEC:

8.6 meq/100 g soil d.w.

Matrix no.:

#9

Matrix type:

Spodsol

% Clay:

3.8

% Org. carbon:

1.98

pH:

4.3

CEC:

2.7 meq/100 g soil d.w.

Matrix no.:

#10

Matrix type:

other: Fine-loamy, mixed, mesic Typic Haplaquoll

% Clay:

23.9

% Org. carbon:

4.39

pH:

7.6

CEC:

48.1 meq/100 g soil d.w.

Matrix no.:

#11

Matrix type:

other: mised, mesic typic udipsament

% Clay:

2.8

% Org. carbon:

2.03

pH:

5.3

CEC:

2 meq/100 g soil d.w.

Details on matrix:

pH
Alligator 4.8
Calciorthid 8.5
Cecil 5.7
Kula 5.9
Lafitte 3.9
Molokai 6
Norwood 6.9
Olivier 6.6
Spodosol 4.3
Webster 7.6
Windsor 5.3

Sample name soil classification
Alligator very fine, montmorillonitic acid, thermic vertic haplaquept
Calciorthid Calciorthid
Cecil clayey, kaolinitic, thermic typic hapludult
Kula medial, isothermic typic eithandept
Lafitte euic, thermic typic medisaprist
Molokai clayey, kaolinitic, isohyperthermic typic torrox
Norwood fine-silty mixed (calc.) thermic typic udifluvent
Olivier fine-silty, mixed thermic awuic fragiudalf
Spodosol Spodosol
Webster Fine-loamy, mixed, mesic Typic Haplaquoll
Windsor mised, mesic typic udipsament

Sample name Organic carbon content (%)
Alligator 1.54
Calciorthid 0.44
Cecil 0.61
Kula 6.62
Lafitte 11.6
Molokai 1.67
Norwood 0.21
Olivier 0.83
Spodosol 1.98
Webster 4.39
Windsor 2.03

clay content (%)
Alligator 54.7
Calciorthid 10.7
Cecil 8.3
Kula 0.9
Lafitte 17.6
Molokai 28.2
Norwood 2.8
Olivier 6.2
Spodosol 3.8
Webster 23.9
Windsor 2.8


CEC ( cmolc/kg (=meq/100g) )
Alligator 30.2
Calciorthid 14.7
Cecil 2
Kula 22.5
Lafitte 26.9
Molokai 11
Norwood 4.1
Olivier 8.6
Spodosol 2.7
Webster 48.1
Windsor 2

Details on test conditions:

Addition test substance:
Samples (1 g) of the soil was mized with 10 ml aliquots of the solutions. The samples were shaken for 18h at 100 osc/min, filtered through quantitative gilfer paper
Added test concentrations (mg/L): 0.01, 0.05, 0.1, 0.2, 0.5, 1, 5, 10, 50, 100
equilibration period: 18h
solid:liquid ratio: 1:10
solution: 0.005M Ca(NO3)2

Duration:

18 h

Remarks:

all samples

Computational methods:

batch equilibrium method; S=Kd*C^n met C= mg/L
Kd calculated for C = 10 µg/L

Sample No.:

#1

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.407 L/kg

pH:

4.8

Remarks on result:

other: Alligator

Sample No.:

#2

Phase system:

solids-water in soil

Type:

log Kp

Value:

1.84 L/kg

pH:

8.5

Remarks on result:

other: Calciorthid

Sample No.:

#3

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.061 L/kg

pH:

5.7

Remarks on result:

other: Cecil

Sample No.:

#4

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.252 L/kg

pH:

5.9

Remarks on result:

other: Kula

Sample No.:

#5

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.357 L/kg

pH:

3.9

Remarks on result:

other: Lafitte

Sample No.:

#6

Phase system:

solids-water in sediment

Type:

log Kp

Value:

3.072 L/kg

pH:

6

Remarks on result:

other: Molokai

Sample No.:

#7

Phase system:

solids-water in soil

Type:

log Kp

Value:

1.911 L/kg

pH:

6.9

Remarks on result:

other: Norwood

Sample No.:

#8

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.567 L/kg

pH:

6.6

Remarks on result:

other: Olivier

Sample No.:

#9

Phase system:

solids-water in soil

Type:

log Kp

Value:

1.679 L/kg

pH:

4.3

Remarks on result:

other: Spodosol

Sample No.:

#10

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.077 L/kg

pH:

7.6

Remarks on result:

other: Webster

Sample No.:

#11

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.819 L/kg

pH:

5.3

Remarks on result:

other: Windsor

	Freundlich adsorption coefficient	Slope Freundlich adsorption isotherm (n)
Alligator	47.75	0.64
Calciorthid	8.87	0.55
Cecil	19.82	0.62
Kula	1499.68	1.46
Lafitte	70.96	0.75
Molokai	156.31	0.56
Norwood	8.53	0.51
Olivier	46.03	0.55
Spodosol	18.75	0.80
Webster	23.60	0.65
Windsor	104.95	0.60

Validity criteria fulfilled:

not specified

Conclusions:

No guideline followed, but study well performed and well documented. Adsorption experiment resulted in 11 log Kp (solids-water in soil) values between 1.70 and 3.07 L/kg dw. All values were used for derivation of the Kp (solids-water in soil) for the chemical safety assessment.

Reference 2

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

batch equilibration method.

GLP compliance:

not specified

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

no

Test temperature:

room temperature

Analytical monitoring:

yes

Details on sampling:

solid phase: air-dried and sieved (2 mm),
medium: 0-15 cm
solution phase: centrifugation at 4000 rpm, filter through a Whatman grade 42 filter paper
sampling location: USA

Matrix no.:

#1

% Clay:

5

pH:

7.7

Matrix no.:

#2

% Clay:

10

pH:

8

Matrix no.:

#3

% Clay:

10

pH:

8.1

Matrix no.:

#4

% Clay:

28

pH:

7.2

Details on matrix:

pH
amarillo: 7.7
arvana: 8
patricia: 8.1
pullmann: 7.2

clay content
amarillo: 5 %
arvana: 10 %
patricia: 10 %
pullmann: 28 %

Details on test conditions:

Added test concentrations: 0, 1, 5, 10, 20, 50, 100, 500 mg/kg
Background conc.: < 1 (negligible)
solid:liquid ratio: 01:10
Addition test substance: 24h equilibratation with potassium arsenate

Computational methods:

adsorption curves were fitted with Freundlich equation. Kp was calculated based on Freundlich parameters for an equilibrium As concentration of 0.01 mg As/L.

Sample No.:

#1

Phase system:

solids-water in soil

Type:

log Kp

Value:

0.1 L/kg

Temp.:

20 °C

pH:

7.7

Remarks on result:

other: amarillo

Sample No.:

#2

Phase system:

solids-water in soil

Type:

log Kp

Value:

1 L/kg

Temp.:

20 °C

pH:

8

Remarks on result:

other: arvana

Sample No.:

#3

Phase system:

solids-water in soil

Type:

log Kp

Value:

1.1 L/kg

Temp.:

20 °C

pH:

8.1

Remarks on result:

other: patricia

Sample No.:

#4

Phase system:

solids-water in soil

Type:

log Kp

Value:

2 L/kg

Temp.:

20 °C

pH:

7.2

Remarks on result:

other: pullmann

	Freundlich adsorption coefficient	Slope Freundlich adsorption isotherm (n)
amarillo	1.38	1.014
arvana	5.23	0.868
patricia	5.5	0.842
pullmann	21.6	0.65

Validity criteria fulfilled:

yes

Conclusions:

No guideline followed, but study well performed and well documented. Adsorption experiment resulted in 4 log Kp (solids-water in soil) values between 0.1 and 2.0 L/kg dw. All values were used for derivation of the Kp (solids-water in soil) for the chemical safety assessment.

Reference 3

Endpoint:

adsorption / desorption: screening

Remarks:

adsorption

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

batch equilibration method.

GLP compliance:

not specified

Type of method:

batch equilibrium method

Media:

soil

Specific details on test material used for the study:

Na2HAsO4.7H2O

Radiolabelling:

no

Test temperature:

25 °C

Analytical monitoring:

yes

Details on sampling:

depth of 30 cm, air-dried and sieved (2 mm)
solution phase: centrifuged and filtered

Matrix no.:

#1

Matrix type:

other: down gradient agricultural soil

% Clay:

28

pH:

6.5

Matrix no.:

#2

Matrix type:

other: down gradient agricultural soil

% Clay:

38

pH:

6.7

Matrix no.:

#3

Matrix type:

other: down gradient agricultural soil

% Clay:

38

pH:

6.5

Matrix no.:

#4

Matrix type:

other: down gradient agricultural soil

% Clay:

41

pH:

6.8

Matrix no.:

#5

Matrix type:

other: down gradient agricultural soil

% Clay:

44

pH:

6.1

Matrix no.:

#6

Matrix type:

other: down gradient agricultural soil

% Clay:

31

pH:

6.4

Matrix no.:

#7

Matrix type:

other: down gradient agricultural soil

% Clay:

36

pH:

5.9

Matrix no.:

#8

Matrix type:

other: down gradient agricultural soil

% Clay:

41

pH:

6.3

Details on matrix:

location: Korea
all samples are down gradient agricultural soil
Background conc. of As: n/a, As free soil
Clay content
DY2: 28%
DY3: 38 %
DY4: 38 %
DY5: 41 %
DY6: 44 %
BS2: 31 %
BS3: 36 %
BS4: 41 %

pH:
DY2: 6.5
DY3: 6.7
DY4: 6.5
DY5: 6.8
DY6: 6.1
BS2: 6.4
BS3: 5.9
BS4: 6.3

Details on test conditions:

Addition test substance:
As solutions were added to the polypropylene centrifuge tubes at a soil mass to solution vol- ume ratio of 1:20, with each sample prepared in triplicate. After attaining equilibrium in a rotary shaker at 25 °C for 36 h, the tubes were centrifuged and the pH of the aqueous phase measured.
Added test concentrations: 5 different concentrations up to 10 mg/L

solution: Na2HAs O47H2O diluted with appropriate volumes of CaCl2

solid:liquid ratio: 01:20

Duration:

1.5 d

Remarks:

all samples

Computational methods:

For the adsorption isotherms, the concentration of As adsorbed (Cs, mg/kg) was calculated by subtracting the mass of As in the equilibrated solution from that initially spiked. The adsorption iso- therm data were fitted to the Freundlich isotherm model: Cs = Kf CNw, where, Cw = As concentration in the aqueous phase (mg/L); Kf = the Freundlich coefficient); and N = a measure of the isotherm nonlinearity (unitless).
The Kp values were calculated for Cw = 10 µg As/L.

Sample No.:

#1

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.2 L/kg

Temp.:

25 °C

pH:

6.5

Remarks on result:

other: DY2

Sample No.:

#2

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.14 L/kg

Temp.:

25 °C

pH:

6.7

Remarks on result:

other: DY3

Sample No.:

#3

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.19 L/kg

Temp.:

25 °C

pH:

6.5

Remarks on result:

other: DY4

Sample No.:

#4

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.38 L/kg

Temp.:

25 °C

pH:

6.8

Remarks on result:

other: DY5

Sample No.:

#5

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.43 L/kg

Temp.:

25 °C

pH:

6.1

Remarks on result:

other: DY6

Sample No.:

#6

Phase system:

solids-water in sediment

Type:

log Kp

Value:

3.36 L/kg

Temp.:

25 °C

pH:

6.4

Remarks on result:

other: BS2

Sample No.:

#7

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.36 L/kg

Temp.:

25 °C

pH:

5.9

Remarks on result:

other: BS3

Sample No.:

#8

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.48 L/kg

Temp.:

25 °C

pH:

6.3

Remarks on result:

other: BS4

	concentration solid phase	concentration solution phase (drinking water WHO limit)
	mg As/kg	mg As/L
DY2	16.01	0.01
DY3	13.73	0.01
DY4	15.67	0.01
DY5	23.76	0.01
DY6	27.11	0.01
BS2	23.00	0.01
BS3	39.87	0.01
BS4	29.97	0.01

Validity criteria fulfilled:

yes

Conclusions:

No guideline followed, but study well performed and well documented. Adsorption experiment resulted in 8 log Kp (solids-water in soil) values between 3.14 and 3.60 L/kg dw. All values were used for derivation of the Kp (solids-water in soil) for the chemical safety assessment.

Reference 4

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

batch equilibration method.

GLP compliance:

not specified

Type of method:

batch equilibrium method

Media:

soil

Test temperature:

not reported

Analytical monitoring:

yes

Details on sampling:

location: Spain
medium: surfacte soil

Matrix no.:

#1

% Clay:

23.6

% Org. carbon:

5.43

pH:

7.96

CEC:

21.4 meq/100 g soil d.w.

Matrix no.:

#2

% Clay:

11.8

% Org. carbon:

0.42

pH:

8.67

CEC:

9.83 meq/100 g soil d.w.

Matrix no.:

#3

% Clay:

7.7

% Org. carbon:

0.38

pH:

8.79

CEC:

2.94 meq/100 g soil d.w.

Matrix no.:

#4

% Clay:

19

% Org. carbon:

0.61

pH:

6.74

CEC:

9.91 meq/100 g soil d.w.

Matrix no.:

#5

% Clay:

23.8

% Org. carbon:

8.22

pH:

7.2

CEC:

25.9 meq/100 g soil d.w.

Matrix no.:

#6

% Clay:

8.31

% Org. carbon:

0.49

pH:

5.87

CEC:

3.83 meq/100 g soil d.w.

Matrix no.:

#7

% Clay:

54.7

% Org. carbon:

0.66

pH:

7.03

CEC:

15.5 meq/100 g soil d.w.

Details on matrix:

pH
H1 7.96
H2 8.67
H3 8.79
H4 6.74
H5 7.2
H6 5.87
H7 7.03

Organic carbon (%)
H1 5.43
H2 0.42
H3 0.38
H4 0.61
H5 8.22
H6 0.49
H7 0.66

clay content (%)
H1 23.6
H2 11.8
H3 7.7
H4 19
H5 23.8
H6 8.31
H7 54.7

CEC cmolc/kg (=meq/100g)
H1 21.4
H2 9.83
H3 2.94
H4 9.91
H5 25.9
H6 3.83
H7 15.5

Background conc. mg As/kg
H1 15.5
H2 9.07
H3 3.39
H4 16.2
H5 12.3
H6 4.39
H7 25.7

Details on test conditions:

Water soluble As concentration in soil was determined from soil:water extracts (1:1 ratio) after 24 h equilibrium with shaking

Duration:

1 d

Remarks:

all samples

Computational methods:

ratio of total As over dissolved As, results for unamended soil only

Sample No.:

#1

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.84 L/kg

pH:

7.96

Remarks on result:

other: H1

Sample No.:

#2

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.11 L/kg

pH:

8.67

Remarks on result:

other: H2

Sample No.:

#3

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.53 L/kg

pH:

8.79

Remarks on result:

other: H3

Sample No.:

#4

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.34 L/kg

pH:

6.74

Remarks on result:

other: H4

Sample No.:

#5

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.01 L/kg

pH:

7.2

Remarks on result:

other: H5

Sample No.:

#6

Phase system:

solids-water in sediment

Type:

log Kp

Value:

2.64 L/kg

pH:

5.87

Remarks on result:

other: H6

Sample No.:

#7

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.41 L/kg

pH:

7.03

Remarks on result:

other: H7

	Concentration solution phase (mg As/L)	concentration solid phase (mg As/kg)
H1	0.023	15.5
H2	0.007	9.07
H3	0.01	3.39
H4	0.077	16.2
H5	0.014	12.3
H6	0.01	4.39
H7	0.01	25.7

Validity criteria fulfilled:

not specified

Conclusions:

No guideline followed, but study well performed and well documented. Adsorption experiment resulted in 7 log Kp (solids-water in soil) values between 2.34 and 3.41 L/kg dw. All values were used for derivation of the Kp (solids-water in soil) for the chemical safety assessment.

Reference 5

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

batch equilibration method.

GLP compliance:

not specified

Type of method:

batch equilibrium method

Media:

soil

Specific details on test material used for the study:

Na2HAsO4.7H2O

Radiolabelling:

no

Test temperature:

not reported

Analytical monitoring:

yes

Details on sampling:

location: Germany
Medium: surface soil
solid phase: air-dried and sieved (2 mm)

Matrix no.:

#1

% Clay:

6.9

% Org. carbon:

1.78

pH:

5.6

CEC:

6.61 meq/100 g soil d.w.

Matrix no.:

#2

% Clay:

18.7

% Org. carbon:

2.51

pH:

5.2

CEC:

10.46 meq/100 g soil d.w.

Matrix no.:

#3

% Clay:

43.5

% Org. carbon:

2.75

pH:

7.3

CEC:

24.68 meq/100 g soil d.w.

Matrix no.:

#4

% Clay:

11.3

% Org. carbon:

1

pH:

5.7

CEC:

7.78 meq/100 g soil d.w.

Matrix no.:

#5

% Clay:

30.8

% Org. carbon:

5.1

pH:

6

CEC:

27.98 meq/100 g soil d.w.

Matrix no.:

#6

% Clay:

67.5

% Org. carbon:

21.68

pH:

4.8

CEC:

49.39 meq/100 g soil d.w.

Details on matrix:

pH
LUFA 2.2 soil 5.6
Refesol 05-G 5.2
Refesol 06-A 7.3
Ter Munck 5.7
Woburn 6
Zegveld 4.8

Organic carbon content (%)
LUFA 2.2 soil 1.78
Refesol 05-G 2.51
Refesol 06-A 2.75
Ter Munck 1
Woburn 5.1
Zegveld 21.68

Clay content (5)
LUFA 2.2 soil 6.9
Refesol 05-G 18.7
Refesol 06-A 43.5
Ter Munck 11.3
Woburn 30.8
Zegveld 67.5

CEC (cmolc/kg (=meq/100g))
LUFA 2.2 soil 6.61
Refesol 05-G 10.46
Refesol 06-A 24.68
Ter Munck 7.78
Woburn 27.98
Zegveld 49.39

Background conc. (mg/kg)
LUFA 2.2 soil 2.99
Refesol 05-G 4.36
Refesol 06-A 4.81
Ter Munck 2.95
Woburn 46.2
Zegveld 12.2

Details on test conditions:

Addition test substance: batch equilibrium method; 8 to 15 initial concentrations; ionic strength adjusted to each single soil sample, suspensions centrifugated and filtered through 0.45 µm
equilibration period: 1 day
solution:
LUFA 2.2 soil 5.25 mM Ca(NO3)2 solution
Refesol 05-G 1 mM Ca(NO3)2 solution
Refesol 06-A 2.75 mM Ca(NO3)2 solution
Ter Munck 6.5 mM Ca(NO3)2 solution
Woburn 1.75 mM Ca(NO3)2 solution
Zegveld 6.5 mM Ca(NO3)2 solution

solid:liquid ratio: 1:5

Computational methods:

batch equilibrium method; S=Kd*C^n met C= mg/L

Sample No.:

#1

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.67 L/kg

pH:

5.6

Remarks on result:

other: LUFA 2.2 soil

Sample No.:

#2

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.76 L/kg

pH:

5.2

Remarks on result:

other: Refesol 05-G

Sample No.:

#3

Phase system:

solids-water in soil

Type:

log Kp

Value:

4.06 L/kg

pH:

7.3

Remarks on result:

other: Refesol 06-A

Sample No.:

#4

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.38 L/kg

pH:

5.7

Remarks on result:

other: Ter Munck

Sample No.:

#5

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.11 L/kg

pH:

6

Remarks on result:

other: Woburn

Sample No.:

#6

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.28 L/kg

pH:

4.8

Remarks on result:

other: Zegveld

	Freundlich adsorption coefficient	Slope Freundlich adsorption isotherm (n)
LUFA 2.2 soil	510	0.52
Refesol 05-G	1216	0.66
Refesol 06-A	1739	0.59
Ter Munck	366	0.59
Woburn	467	0.78
Zegveld	835	0.82

	concentration solid phase (mg/kg)
LUFA 2.2 soil	46.51
Refesol 05-G	58.20
Refesol 06-A	114.89
Ter Munck	24.18
Woburn	12.86
Zegveld	19.13

concentration solution phase: 0.01  mg As/L - WHO drinking water limit

Validity criteria fulfilled:

yes

Conclusions:

No guideline followed, but study well performed and well documented. Adsorption experiment resulted in 6 log Kp (solids-water in soil) values between 3.11 and 4.06 L/kg dw. All values were used for derivation of the Kp (solids-water in soil) for the chemical safety assessment.

Reference 6

Endpoint:

adsorption / desorption: screening

Remarks:

adsorption

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

batch equilibration method.

GLP compliance:

not specified

Type of method:

batch equilibrium method

Media:

soil

Specific details on test material used for the study:

As(III)

Radiolabelling:

no

Test temperature:

room temperature

Analytical monitoring:

yes

Details on sampling:

Medium: subsurface
location: Japan
air-dried and sieved (0.4 mm)
solution phase: centrifugatiion and filtered through a 0.45µm filter

Matrix no.:

#1

% Clay:

48

% Org. carbon:

3.2

pH:

5.8

CEC:

16.3 meq/100 g soil d.w.

Matrix no.:

#2

% Clay:

30

% Org. carbon:

2.1

pH:

5.3

CEC:

16.2 meq/100 g soil d.w.

Matrix no.:

#3

% Clay:

36

% Org. carbon:

18.7

pH:

5.2

CEC:

20.7 meq/100 g soil d.w.

Matrix no.:

#4

% Clay:

20

% Org. carbon:

6.3

pH:

4.9

CEC:

18.5 meq/100 g soil d.w.

Matrix no.:

#5

% Clay:

11

% Org. carbon:

6.1

pH:

5.8

CEC:

23 meq/100 g soil d.w.

Matrix no.:

#6

% Clay:

23

% Org. carbon:

91.7

pH:

5

CEC:

20.2 meq/100 g soil d.w.

Matrix no.:

#7

% Clay:

13

% Org. carbon:

21.4

pH:

5.9

CEC:

6.9 meq/100 g soil d.w.

Matrix no.:

#8

% Clay:

59

% Org. carbon:

1.7

pH:

5.3

CEC:

24.9 meq/100 g soil d.w.

Matrix no.:

#9

% Clay:

36

% Org. carbon:

2.1

pH:

4.6

CEC:

14.4 meq/100 g soil d.w.

Matrix no.:

#10

% Clay:

29

% Org. carbon:

9.7

pH:

5.6

CEC:

16.1 meq/100 g soil d.w.

Matrix no.:

#11

% Clay:

6

% Org. carbon:

4.7

pH:

4.7

CEC:

2.6 meq/100 g soil d.w.

Matrix no.:

#12

% Clay:

22

% Org. carbon:

9.6

pH:

5.5

CEC:

14.1 meq/100 g soil d.w.

Matrix no.:

#13

% Clay:

34

% Org. carbon:

14.1

pH:

5.4

CEC:

5.9 meq/100 g soil d.w.

Matrix no.:

#14

% Clay:

18

% Org. carbon:

8.7

pH:

5.8

CEC:

16.1 meq/100 g soil d.w.

Matrix no.:

#15

% Clay:

60

% Org. carbon:

23.3

pH:

5.3

CEC:

6.6 meq/100 g soil d.w.

Details on matrix:

pH
1 5.8
2 5.3
3 5.2
4 4.9
5 5.8
6 5
7 5.9
8 5.3
9 4.6
10 5.6
11 4.7
12 5.5
13 5.4
14 5.8
15 5.3

Organic carbon content (%)
1 3.2
2 2.1
3 18.7
4 6.3
5 6.1
6 91.7
7 21.4
8 1.7
9 2.1
10 9.7
11 4.7
12 9.6
13 14.1
14 8.7
15 23.3

Clay content (%)
1 48
2 30
3 36
4 20
5 11
6 23
7 13
8 59
9 36
10 29
11 6
12 22
13 34
14 18
15 60
CEC cmolc/kg (=meq/100g)
1 16.3
2 16.2
3 20.7
4 18.5
5 23
6 20.2
7 6.9
8 24.9
9 14.4
10 16.1
11 2.6
12 14.1
13 5.9
14 16.1
15 6.6

Details on test conditions:

Addition test substance: 0.2g soil + 40mL of 10mM CaSO4 mixed in a polypropylene centrifuge tube
Added test concentrations: varying, 4-80 µg As per 0.2 g soil
equilibration period: 1 day
solution: 10 mM CaSO4
solid:liquid ratio: 1:200

Computational methods:

Q=KdC where Q is the quantity (µg/g) of As(III) adsorbed per gram of soil and C is the equilibrium concentration (µg/mL) of As(III) in solution.

Sample No.:

#1

Phase system:

solids-water in soil

Type:

log Kp

Value:

3.08 L/kg

Temp.:

20 °C

pH:

5.8

Sample No.:

#2

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.28 L/kg

Temp.:

20 °C

pH:

5.3

Sample No.:

#3

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.3 L/kg

Temp.:

20 °C

pH:

5.2

Sample No.:

#4

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.89 L/kg

Temp.:

20 °C

pH:

4.9

Sample No.:

#5

Phase system:

solids-water in soil

Type:

log Kp

Value:

1.88 L/kg

Temp.:

20 °C

pH:

5.8

Sample No.:

#6

Phase system:

solids-water in sediment

Type:

log Kp

Value:

2.08 L/kg

Temp.:

20 °C

pH:

5

Sample No.:

#7

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.38 L/kg

Temp.:

20 °C

pH:

5.9

Sample No.:

#8

Phase system:

solids-water in soil

Type:

log Kp

Value:

1.88 L/kg

Temp.:

20 °C

pH:

5.3

Sample No.:

#9

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.43 L/kg

Temp.:

20 °C

pH:

4.6

Sample No.:

#10

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.38 L/kg

Temp.:

20 °C

pH:

5.6

Sample No.:

#11

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.99 L/kg

Temp.:

20 °C

pH:

4.7

Sample No.:

#12

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.38 L/kg

Temp.:

20 °C

pH:

5.5

Sample No.:

#13

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.18 L/kg

Temp.:

20 °C

pH:

5.4

Sample No.:

#14

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.18 L/kg

Temp.:

20 °C

pH:

5.8

Sample No.:

#15

Phase system:

solids-water in soil

Type:

log Kp

Value:

2.48 L/kg

Temp.:

20 °C

pH:

5.3

Validity criteria fulfilled:

not specified

Conclusions:

No guideline followed, but study well performed and well documented. Adsorption experiment resulted in 15 log Kp (solids-water in soil) values between 1.88 and 3.08 L/kg dw. All values were used for derivation of the Kp (solids-water in soil) for the chemical safety assessment.

Reference 7

Endpoint:

adsorption / desorption: screening

Remarks:

adsorption

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

batch equilibration method.

GLP compliance:

not specified

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

no

Test temperature:

not reported

Analytical monitoring:

yes

Details on sampling:

location: Berlin
Medium: 0-25 cm
soil classification: sandy combisol
solid phase: aqua regia extraction
solution phase: via a perfusion apparatus

Matrix no.:

#1

Matrix type:

other: sandy combisol

% Clay:

9

% Silt:

12

% Sand:

79

% Org. carbon:

1.2

pH:

6

CEC:

10.3 meq/100 g soil d.w.

Details on matrix:

pH: 6,
Organic carbon content: 1.2%
Clay content: 9%
CEC: 10.3 cmolc/kg (=meq/100g)
other properties: 12% silt, 79% sand

Details on test conditions:

Addition test substance: percolation of 50 g soil with 100 ml distilled water at 26°C for 4 days
Added test concentrations: 50 mg/kg
equilibration period: 4days
solution: distilled water
solid:liquid ratio: 1:2

Duration:

4 d

pH:

6

Computational methods:

ratio of sorbed concentration in soil over not sorbed concentration

Sample No.:

#1

Phase system:

solids-water in soil

Type:

log Kp

Value:

1.52 L/kg

pH:

6

Concentration solution phase

0.68 mg As/L

concentration solid phase

22.7  mg As/kg

Validity criteria fulfilled:

not specified

Conclusions:

No guideline followed, but study well performed and well documented. Adsorption experiment resulted in 1 log Kp (solids-water in soil) value, 1.52 L/kg dw. This value was used for derivation of the Kp (solids-water in soil) for the chemical safety assessment.

Description of key information

Soil: The median log Kp of 2.50 L/kg dry weight from experimental results for 52 soils from 7 studies was selected for the partitioning of As between solids and water in soil.

Freshwater sediment: The median log Kp value of 3.68 L/kg dry weight from experimental data for 7 rivers derived from 7 studies was selected for the partitioning of As between solids and water in freshwater sediment.

Marine sediment: The median log Kp value of 3.13 L/kg dry weight from experimental data for 2 marine systems derived from 2 studies was selected for the partitioning of As between solids and water in marine sediment.

Freshwater suspended mater: The median log Kp value of 4.10 L/kg dry weight from experimental data for 13 freshwater systems derived from 13 studies was selected for the partitioning of As between solids and water in freshwater suspended matter.

Marine suspended mater: The median log Kp value of 3.88 L/kg dry weight from experimental data for 6 marine systems derived from 5 studies was selected for the partitioning of As between solids and water in marine suspended matter.

Key value for chemical safety assessment

Other adsorption coefficients

Type:

log Kp (solids-water in soil)

Value in L/kg:

2.5

Other adsorption coefficients

Type:

log Kp (solids-water in suspended matter)

Value in L/kg:

4.1

Other adsorption coefficients

Type:

other: log Kp (solids-water in marine suspended matter)

Value in L/kg:

3.88

Other adsorption coefficients

Type:

log Kp (solids-water in sediment)

Value in L/kg:

3.68

Other adsorption coefficients

Type:

other: log Kp (solids-water in marine sediment)

Value in L/kg:

3.13

Additional information

There is substantial reliable (all Klimisch 2) information available for adsorption/desorption of arsenic, reporting partitioning coefficients (Kp values, i.e. ratio of As concentration in solid phase over dissolved As concentration in solution phase) for soil, sediments and suspended matter. All the information available for sediment and suspended matter is based on paired monitoring data of elemental As concentrations in sediment or suspended matter and water. The reliable information for Kp values in soil is based on batch adsorption or desorption experiments with added As(III) and As(V) salts.

 

Soil

For soil, seven studies were identified, which report reliable Kp values for As(III) and As(V) salts in 52 soils with varying properties (pH: 3.9-8.8; organic carbon: 0.2-21.7%; clay: 1-68%). Log Kp values range between 0.11 and 4.06 L/kg dry weight, with a median of 2.50 L/kg dry weight. No significant differences were observed in Kp values between As salts added to the soils and Kp values were not strongly correlated with soil properties. Results summarized in several review documents are largely in the range of the 52 Kp values selected from the 7 experimental studies identified. According to Allison and Allison (2005), 21 log Kp values for soils range from 0.3 to 4.3 L/kg without differentiating between As(III) and As(V) and thus possibly involving both oxidation states. The median, mean and standard deviation assuming a log-normal distribution are 3.4, 3.2 and 0.7 L/kg, respectively. In addition, Crommentuijn et al. (1997) reported log Kp values between 2.28 and 3.61 L/kg. Sauve et al. (2000) summarized 66 log Kp values, including studies using metal-spiked soils, ranging from 0.2 to 5.72 L/kg.

The median log Kp of 2.50 L/kg dry weight from results for the 52 soils was selected for the partitioning of As between solids and water in soil for the chemical safety assessment.

 

Sediment

All the information available for Kp values in sediment is based on paired monitoring data of total elemental As concentrations in sediment and dissolved As concentrations in corresponding pore water or overlying water. For freshwater sediment, 7 studies were identified that report reliable Kp values for As in 7 river systems from China (2), Japan, South- Africa, South Korea, USA and Vietnam. For each river, an average log Kp value was calculated based on all individual data reported. Log Kp values for As in sediment of the 7 river systems vary between 2.63 and 4.03 L/kg dry weight, with a median of 3.68 L/kg dry weight. Two reliable studies were identified for Kp values of As in marine sediments, reporting Kp data for 2 marine systems (Jiaozhou Bay, China and Youngsan River Estuary, South Korea). Average log Kp values for each location are 4.09 and 2.17 L/kg, respectively, with a median of 3.13 L/kg dry weight.

Values summarized in reviews by Allison and Allison (2005) and Crommentuijn et al. (1997) are in the range of the Kp values selected from the experimental studies identified. According to Allison and Allison (2005), log Kp values for freshwater sediments range from 1.6 to 4.3 L/kg without differentiating between As(III) and As(V) and thus possibly involving both oxidation states. The median, mean and standard deviation based on a log-normal distribution are 2.2, 2.4 and 0.7 L/kg, respectively. Crommentuijn et al. (1997) reported log Kp values of 4.07L/kg based on monitoring data in freshwater sediments from 3 different locations in the Netherlands and a log Kp value of 3.99L/kg based on monitoring data in marine surface water and sediments at different locations in the North Sea and Wadden Sea.

The median log Kp values of 3.68 and 3.13 L/kg dry weight were selected for the partitioning of As between solids and water in freshwater and marine sediment, respectively, for the chemical safety assessment.

 

Suspended matter

All the information available for Kp values in suspended matter is based on paired monitoring data of total elemental As concentrations in suspended matter and dissolved As concentrations in corresponding water samples. Reliable data for Kp of As in suspended matter was identified for 13 freshwater systems from Canada, China (4), Czech Republic, Japan, Mexico, Morocco, South Korea (2), the Netherlands and Vietnam. For each freshwater system, an average log Kp value was calculated based on all individual data reported. Log Kp values for As in suspended matter for the 13 freshwater systems vary between 2.86 and 4.97 L/kg dry weight, with a median of 4.10 L/kg dry weight. In addition, 5 studies were identified with reliable data for partitioning of As in marine suspended matter for 6 locations from China (2), South Korea (2), the Netherlands and the United Kingdom. For each location, an average log Kp value was calculated based on all individual data reported. Log Kp values for As in suspended matter for the 6 marine systems vary between 3.04 and 4.47 L/kg dry weight, with a median of 3.88 L/kg dry weight.

Values summarized in reviews by Allison and Allison (2005) and Crommentuijn et al. (1997) are in the range of the Kp values selected from these experimental studies identified. According to Allison and Allison (2005), 25 log Kp values for suspended matter range from 2.0 to 6.0 L/kg without differentiating between As(III) and As(V) and thus possibly involving both oxidation states. The median, mean and standard deviation assuming a log-normal distribution are 4.0, 3.9 and 0.5 L/kg, respectively. Crommentuijn et al. (1997) reported log Kp values of 4.00 and 4.08 L/kg based on freshwater monitoring data from different locations in the Netherlands and log Kp values of 3.45 and 3.85 L/kg based on marine monitoring data from different locations in the North Sea and Wadden Sea.

The median log Kp values of 4.10 and 3.88 L/kg dry weight were selected for the partitioning of As between solids and water in freshwater and marine suspended matter, respectively, for the chemical safety assessment.

Medium	Test substance	Log Kp (L/kg)	# data	Reference
Soil
Subsurface soils, Japan	As(III) salt (not specified)	1.88 – 3.08	15	Sakata, 1987
Natural soils, USA	Na2HAsO4.7H2O	1.68 – 3.07	11	Buchter et al., 1989
Natural soil, Germany	Na salt (not specified)	1.52	1	Wilke, 1989
Agricultural soils, South Korea	Na2HAsO4.7H2O	3.14 – 3.60	8	Nam et al., 2010
Alkaline soils from Southern High Plains, USA	KH2AsO4	0.11 – 2.03	4	Kandajaki et al., 2015
Natural soils, Spain	Arsenic background concentration in soil	2.34-3.41	7	Romero-Freire et al., 2015
Natural soils, Germany, Belgium, the Netherlands and UK	Na2HAsO4.7H2O	3.11 – 4.06	6	Römbke et al., 2020
Sediment, freshwater
Blesbokspruit, South- Africa	Monitoring of elemental As concentrations	3.48 (2.85 – 4.62)	19	Roychoudhury and Starke, 2006
To Lich and Kim Nguu rivers, Vietnam	Monitoring of elemental As concentrations	3.68	1	Marcussen et al., 2008
Rio Grande, Texas, USA	Monitoring of elemental As concentrations	2.88 (2.08 – 3.33)	12	Baeza et al., 2010
Ichinokawa River, Japan	Monitoring of elemental As concentrations	3.82 (3.30 – 4.35)	8	Asaoka et al., 2012
Hengshi River, China	Monitoring of elemental As concentrations	3.99 (3.83 – 4.16)	2	Liao et al., 2017
Youngsan River, South Korea	Monitoring of elemental As concentrations	2.63 (2.42 – 2.73)	5	Hong et al., 2018
Beijiang River, China	Monitoring of elemental As concentrations	4.03 (3.48 – 4.37)	9	Li et al., 2018
Sediment, marine water
Youngsan River Estuary, South Korea	Monitoring of elemental As concentrations	2.17 (1.86 – 2.47)	5	Hong et al., 2018
Jiaozhou Bay, China	Monitoring of elemental As concentrations	4.09 (4.06 – 4.11)	2	Gu et al., 2020
Suspended matter, freshwater
Rio Grand, Mexico	Monitoring of elemental As concentrations	2.86 (2.61 – 3.19)	3	Popp and Laquer, 1980
Lake Yssel, the Netherlands	Monitoring of elemental As concentrations	3.71 (3.65 – 3.76)	3	Van der Sloot et al, 1985
Czech Rivers	Monitoring of elemental As concentrations	4.43	1	Vesely et al., 2001
St Lawrence river, Canada	Monitoring of elemental As concentrations	4.10	1	Gobeil et al., 2005
Fez and Sebou Rivers, Morocco	Monitoring of elemental As concentrations	3.86 (3.35 – 4.11)	4	Koukal et al., 2005
Ichinokawa River, Japan	Monitoring of elemental As concentrations	3.87 (2.97 – 4.41)	3	Asaoka et al., 2012
Wanquan River and Wenchang/Wenjiao River, China	Monitoring of elemental As concentrations	4.58	1	Balzer et al., 2013
Day River, Vietnam	Monitoring of elemental As concentrations	4.80 (4.56 – 5.15)	10	Duc et al., 2013
Taehwa River, South Korea	Monitoring of elemental As concentrations	3.29 (2.28 – 3.78)	12	Hong et al., 2016
freshwater lakes, China	Monitoring of elemental As concentrations	4.97 (4.61 – 5.19)	4	Yang et al., 2016
Hengshi River, China	Monitoring of elemental As concentrations	4.21 (4.17 – 4.24)	2	Liao et al., 2017
Youngsan River, South Korea	Monitoring of elemental As concentrations	3.97 (3.88 – 4.11)	5	Hong et al., 2018
Beijiang River, China	Monitoring of elemental As concentrations	4.28 (4.19 – 4.42)	7	Li et al., 2018
Suspended matter, marine water
The southern Bright and British Channel, UK	Monitoring of elemental As concentrations	4.47 (4.08 – 5.10)	7	Van der Sloot et al, 1985
Wadden Sea, the Netherlands	Monitoring of elemental As concentrations	4.01 (3.92 – 4.12)	11	Van der Sloot et al, 1985
Estuary of Wanquan River and Wenchang/Wenjiao River, China	Monitoring of elemental As concentrations	4.22	1	Balzer et al., 2013
Taehwa River Estuary, South Korea	Monitoring of elemental As concentrations	3.39 (3.02 – 3.87)	8	Hong et al., 2016
Youngsan River Estuary, South Korea	Monitoring of elemental As concentrations	3.04 (2.88 – 3.22)	5	Hong et al., 2018
Jiaozhou Bay, China	Monitoring of elemental As concentrations	3.75 (3.73 – 3.76)	2	Gu et al., 2020