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Environmental fate & pathways

Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption, other
Remarks:
monitoring data in water and sediment
Type of information:
other: Calculation of Kp values based on environmental field data
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Kp-values are based on reliable field data of concentration levels in water and sediment; no standard guideline test was conducted to generate Kp-values. Kp-values are calculated based on the hypothesis that equilibrium exists between the baseline levels in water and in sediment.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Evaluation of high quality environmental geochemical data for Europe, which is provided by the Forum of European Geological Surveys (FOREGS), with respect to calcium (Ca) concentrations in stream water and stream sediment. Baseline levels of calcium in water and sediment were determined in 745 paired sample locations. Assuming equilibrium between both environmental compartments, site-specific partitioning coefficients (Kp) were derived.
GLP compliance:
no
Type of method:
other: field data of baseline levels in water and sediment
Media:
sediment
Radiolabelling:
no
Test temperature:
environmental relevant temperatures
Analytical monitoring:
yes
Details on sampling:
FOREGS:
-The FOREGS sampling grid was based on GTN grid cells developed for Global Geochemical Baseline mapping. This grid divides the entire land surface into 160 km x 160 km cells covering an area of 4,500,000 km2.
- Sampling methodology, preparation and analysis are described by Salminen et al. (2005).
- A total of 808 stream water samples and 852 sediment samples were processed in the FOREGS-program, including 757 paired samples, i.e. samples with the same coordinates for the sampling location of stream water and sediment that are summarised below. However, Ca concentrations in 12 stream water samples (3 from Albania and 9 from Switzerland) were excluded from the analysis, resulting in a total of 745 paired samples summarised below.
- High quality and consistency of the obtained data were ensured by using standardised sampling methods and by treating and analysing all samples in the same laboratory of each country.
Key result
Phase system:
sediment-water
Type:
log Kp
Value:
2.73 L/kg
Remarks on result:
other: European 50th percentile log Kp
Adsorption and desorption constants:
The monitoring stream water and sediment data show that Ca concentrations of sediments range from 0.1 to 55 %, while dissolved Ca concentrations in the water column of European stream waters range from 0.2 to 590 mg/L, showing a high exchange of Ca between both environmental matrices. Regarding the partitioning of calcium in the water column, stream water/sediment partition coefficients range from 18 to 209,845 L/kg. Country-specific stream water/sediment partition coefficients are reported in Table 1 with 50th percentile log Kp values ranging from 2.13 to 3.90. Since FOREGS sampled on a grid aiming to equally represent geochemical baseline concentrations across Europe, the 50th percentile log Kp across Europe was determined to be 2.73 L/kg (Table 2).

Table 1: Country-specific stream water/sediment partition coefficients (log Kp)

Country

# of data

Area (km2)

Min

Max

Mean

5thP

50thP

90thP

95thP

AL

3

28,748

2.63

3.28

2.97

2.64

2.71

3.21

3.24

AT

20

83,879

2.28

3.80

3.36

2.45

3.11

3.78

3.79

BE

5

32,545

1.71

2.36

2.12

1.78

2.13

2.29

2.33

CH

9

41,285

2.44

3.69

3.29

2.64

3.10

3.56

3.63

CZ

10

78,866

2.17

3.00

2.67

2.29

2.63

2.92

2.96

DE

74

357,121

1.52

3.60

2.45

1.70

2.14

2.70

2.96

DK

5

43,098

2.13

2.82

2.57

2.23

2.50

2.76

2.79

EE

11

45,227

1.76

3.08

2.57

1.90

2.48

2.89

2.99

ES

85

504,645

1.74

3.52

2.98

2.03

2.78

3.36

3.38

FI

63

338,144

2.68

4.16

3.68

3.04

3.63

3.90

3.98

FR

118

543,965

1.34

4.04

3.05

2.03

2.65

3.47

3.56

GR

27

131,957

1.91

3.42

2.97

2.33

2.82

3.29

3.38

HR

10

56,542

2.15

2.92

2.54

2.19

2.42

2.88

2.90

IE

10

70,273

2.20

4.04

3.51

2.23

3.33

3.76

3.92

IT

45

301,336

1.45

4.68

3.45

2.24

2.99

3.81

3.85

LT

14

64,589

2.43

2.92

2.69

2.44

2.62

2.90

2.92

LV

7

65,301

1.80

2.60

2.38

1.96

2.36

2.58

2.59

NL

9

41,526

1.25

2.66

2.30

1.39

2.25

2.54

2.60

NO

58

323,759

2.20

5.32

4.36

3.03

3.90

4.66

4.87

PL

56

312,685

1.53

3.06

2.24

1.71

2.13

2.42

2.71

PT

19

92,345

1.73

3.41

2.87

1.97

2.62

3.26

3.37

SE

20

449,964

2.57

3.85

3.46

2.72

3.44

3.72

3.75

SK

15

49,034

2.22

3.30

2.72

2.26

2.47

3.05

3.17

SL

4

20,253

2.57

3.38

3.07

2.65

3.00

3.30

3.34

UK

60

219,331

1.81

3.93

3.05

2.00

2.47

3.58

3.79

Table 2: Concentrations of calcium in sediment and water and resulting partition coefficients

 

Ca concentration

Ca concentration

Partitioning (Kd)

Log Kd

Parameter

(sediment)

(water)

Ca (sed / water)

Ca (sed / water)

#

757

7451

757

7451

757

7451

757

7451

Unit

mg/kg

mg/L

L/kg

-

Min.

571.75

571.75

0.23

0.23

17.99

1.25

Max.

397,797.01

397,797.01

592.00

592.00

209,845.44

5.32

Mean

38,695.75

38,160.47

56.43

56.28

3,046.39

3,068.17

2.83

2.82

STDEV

59,451.76

58,953.06

62.41

61.96

12,715.59

12,815.38

0.68

0.69

5thp

2,215.54

2,215.54

1.66

1.64

67.31

66.86

1.83

1.83

50thp

16,294.95

16,009.08

42.70

42.70

536.50

531.84

2.73

2.73

90thp

98,441.54

97,240.86

117.92

118.08

5,762.49

5,815.31

3.76

3.76

95thp

187,063.22

185,633.84

148.22

148.00

8,119.30

8,356.37

3.91

3.92

1Values from Switzerland and Albania are not included.

Conclusions:
Reliable baseline levels of calcium in pristine water/sediment samples were determined in 745 samples. Sampling and analytical procedures are considered adequate and resulted in reliable data. Assuming equilibrium between the typical concentration in water and sediment, relevant log Kp-values were generated. Data are therefore considered useful for the determination of a relevant log Kp for the sediment compartment. Since FOREGS sampled on a grid aiming to equally represent geochemical baseline concentrations across Europe, the 50th percentile concnetraion of calium was 16,009 mg/kg sediment and 42.70 mg/L streamwater, respectively, yielding a median log Kp for calcium across Europe of 2.73 L/kg.

Description of key information

Dissolved calcium has typically a high mobility and, except under strongly alkaline conditions, occurs in solution as dissociated Ca2+ ions. A European median log Kp value of 2.73 is derived for sediment-water partitioning. Dissolved calcium is expected to also be highly mobile in suspended matter and soil.

Key value for chemical safety assessment

Other adsorption coefficients

Type:
log Kp (solids-water in sediment)
Value in L/kg:
2.73

Additional information

The assessment of the partitioning of calcium in freshwater sediments is based on Kp values derived from monitoring data for elemental calcium concentrations in water and corresponding sediments provided by the FOREGS Geochemical Baseline Mapping Programme that aimed to provide high quality, multi-purpose homogeneous environmental geochemical baseline data for Europe. A total of 745 paired samples, i.e. samples with the same coordinates for the sampling location of stream water (filtered to < 0.45 µm) and sediment (wet sieved in the field to <0.15 mm) were processed (Salminen et al. 2005) and results correspond to steady-state conditions of calcium, independent of calcium speciation.

Sampled stream water and sediments cover a wide range of environmental conditions. Water parameters such as pH, hardness and organic carbon concentrations cover several magnitudes. Calcium concentrations of sediments range from < 0.1 % to > 35 % with 5th and 95th percentile of 0.22 and 18.56 %, respectively, whereas dissolved calcium concentrations in the water column of European stream waters range from < 0.3 to > 550 mg/L with 5th and 95th percentile 1.64 and 148.00 mg/L, respectively.

Regarding the partitioning of calcium in the water column, stream water/sediment partition coefficients range from 17.99 L/kg to 209,845.44 L/kg. Since FOREGS sampled on a grid aiming to equally represent geochemical baseline concentrations across Europe, a European median log Kd value of 2.73 is derived for sediment-water partitioning.