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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Soil: According to Allison & Allison (2005), 21 log Kp values for soils range from 0.3 to 4.3 without differentiating between As(III) and As(V) and thus possibly involving both oxidation states. As other relevant published log Kp values are in agreement with Allison & Allison (2005), the median of 3.4 was selected for the chemical safety assessment.
Sediment: According to Allison & Allison (2005), log Kp values for sediments range from 1.6 to 4.3 without differentiating between As(III) and As(V) and thus possibly involving both oxidation states. As other relevant published log Kp values are in agreement with Allison & Allison (2005), the median of 2.2 was selected for the chemical safety assessment.
Suspended matter: According to Allison & Allison (2005), 25 log Kp values for sediments range from 2.0 to 6.0 without differentiating between As(III) and As(V) and thus possibly involving both oxidation states. As other relevant published log Kp values are in agreement with Allison & Allison (2005), the median of 4.0 was selected for the chemical safety assessment.

Key value for chemical safety assessment

Additional information

Data from the following publications, studies and review documents were summarised to quantify partitioning in soils, sediments and suspended matter:

1.Allison & Allison (2005)

2.World Health Organization (2001)

3.Crommentuijn et al (1997)

4. Sauve et al (2000)

 

Partition coefficients for soil, sediments and suspended matter

medium

Median

log10

Mean

log10

SD

log10

Min

log10

Max

log10

n

Review

Soil

3.4

3.2

0.7

0.3

4.3

21

Allison & Allison, 2005

Soil

 

 

 

1.88

3.08

15

WHO, 2001

Soil

 

 

 

2.28

3.61

 

Crommentuijn et al., 1997

Soil

*

*

*

0.2

5.72

66

Sauve et al., 2000

Sediment

2.2

2.4

0.7

1.6

4.3

 

Allison & Allison, 2005

Sediment

 

 

 

 

4.07

 

Crommentuijn et al., 1997

Sediment (marine)

 

 

 

3.99

 

 

Crommentuijn et al., 1997

Suspended matter

4.0

3.9

0.5

2.0

6.0

25

Allison & Allison, 2005

Suspended matter

 

 

 

4.0

4.08

 

Crommentuijn et al., 1997

Suspended matter (marine)

 

 

 

3.45

3.85

 

Crommentuijn et al., 1997

 * As Sauve et al. (2000) provided statistics (Mean, SD, Median) based on untransformed Kp values, these values were not tabulated.

 Soil

·        According to Allison and Allison (2005), 21 log Kp values for soils range from 0.3 to 4.3 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, respectively.

  ·        WHO (2001) cited a study by Sakata (1987) reporting log Kp values for arsenite in 15 subsurface soils from different sites in Japan with log Kp values ranging from 1.88 to 3.08 and being significantly correlated with the extractable iron content of the soils.

  ·        In addition, Crommentuijn et al. (1997) reported log Kp values of 2.28 and 3.61 based on batch experiments by Bockting et al (1992) and field-based data of a polluted site reported by Janssen et al. (1996), respectively.

  ·        Sauve et al. (2000) summarized 66 log Kp values, including studies using metal-spiked soils, ranging from 0.2 to 5.72. However, as the provided statistics (Mean, SD, Median) were computed using untransformed Kp values, these values are not comparable to the statistics provided by Allison & Allison (2005).

Values summarized by Crommentuijn et al. (1997), Sauve et al. (2000) and WHO (2001) are in the range of Kp values as reported for soils by Allison & Allison (2005) except for the maximum reported by Sauve et al. (2000), who included studies using metal-spiked soils. The maximum reported by Sauve et al. (2000) may not be representative for metal partitioning at ambient As concentrations in the soil as it may not be advisable to use Kp values derived from highly contaminated soils and apply them for risk assessment of ambient conditions. Thus, the median of 3.4 reported by Allison & Allison (2005) was selected for the chemical safety assessment.

 

Sediment

·        According to Allison & Allison (2005), log Kp values for sediments range from 1.6 to 4.3 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 distributionare 2.2, 2.4 and 0.7, respectively.

  ·        Crommentuijn et al. (1997) reported log Kp values of 4.07 and 3.99 based on monitoring data in freshwater sediments from 3 different locations in the Netherlands during different time intervals by Venema (1996) and monitoring data in marine surface water and sediments at different locations in the North Sea and Wadden Sea by Yland (1996), respectively.

Values summarized by Crommentuijn et al. (1997) are in the range of Kp values as reported for sediments by Allison & Allison (2005). Thus, the median log Kp value of 2.2 reported by Allison & Allison (2005) was selected for the chemical safety assessment.

 

Suspended matter

·        According to Allison and Allison (2005), 25 log Kp values for suspended matter range from 2.0 to 6.0 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, respectively.

·        Crommentuijn et al. (1997) reported log Kp values of 4.00 and 4.08 based on freshwater monitoring data from 4 different locations in the Netherlands in 1983-1986 by Stortelder et al. (1989) and monitoring data from 7 different locations in the Netherlands in 1988-1992 by Venema (1994), respectively.

·        Crommentuijn et al. (1997) furthermore reported log Kp values of 3.45 and 3.85 based on marine monitoring data from different locations in the North Sea and Wadden Sea in 1995 by Yland (1996) and Yland and Smedes (1996), respectively.

Values summarized by Crommentuijn et al. (1997) are in the range of log Kp values as reported for suspended matter by Allison & Allison (2005). Thus, the median of 4.0 reported by Allison & Allison (2005) was selected for the chemical safety assessment.


Other adsorption coefficient indicated as dimensionless:
- log Kp (solids-water in soil) ,3.4
- log Kp (solids-water in sediment) ,2.2
- log Kp (solids-water in suspended matter) ,4.0