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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.
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.
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.
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.
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.
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.
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

Only few water accommodated fraction (WAF) based acute aquatic ecotoxicity data are available for the poorly soluble substance gallium arsenide (GaAs). For metals and poorly soluble metal compounds, WAF testing should not be used and ecotoxicity information should be derived with tests on a soluble metal salt and differences in solubility addressed by results from transformation/dissolution tests on the poorly soluble compound. Upon dissolution, GaAs yields both soluble gallium and arsenic ions. Because the available toxicity data show that As ions are more toxic in the environment compared to Ga ions, the ecotoxicity of GaAs is predicted based on read across from GaAs to soluble inorganic As compounds. In order to still account for the potential contribution of Ga ions to toxicity of GaAs in the environment, the toxicity results for As ions are not corrected for their abundance in GaAs, which means that the toxicity of Ga is considered similar as As. This is a worst-case scenario based on the available toxicity data for soluble Ga and As compounds.


For further justification of the read-across approach between GaAs and arsenic, see also the justification document attached in IUCLID section 13).


 


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