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Adsorption / desorption

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Description of key information

Key value for chemical safety assessment

Additional information

- Freshwater environment

Partitioning coefficient for Pb between the freshwater and suspended particulate matter (SPM) are summarized in the voluntary risk assessment of lead (LDAI, 2008). An overview of the selected data is provided in the Table below.

Table: Reported log KD,SPM values for Pb in freshwaters in Europe.

Location

Log KD(L/kg)

Remarks

Reference

Four Dutch Lakes

6.0

average

Koelmans and Radovanovic, 1998

Calder River, UK

Nidd River, UK

Swale River, UK

Trent River, UK

All rivers

All rivers

4.45 - 5.98

4.69 - 6.25

4.58 - 6.20

4.61 - 6.06

5.41

5.71

min-max range

min-max range

min-max range

min-max range

observed mean

predicted mean

Lofts and Tipping, 2000

Scheldt, Belgium

5.3

salinity of 1.5 ppm

Nolting et al., 1999

Po River, Italy

5.5

median value

Pettine et al., 1994

Dutch freshwater

5.81

mean

Stortelder et al., 1989; in Crommentuyn et al., 1997

Upland-influenced river water, UK

Low-salinity water, UK

4.6

5.5

modelled value

modelled value

Tipping et al., 1998

7 freshwater locations in The Netherlands

5.93

 

Venema, 1994; in Crommentuyn et al., 1997

54 Czech rivers / 119 locations

5.44

5.18

median KD

median KA(1)

Veselý et al., 2001

RANGE

4.45 – 6.25

 

 

(1)KA: based on the acid soluble concentration

For the calculation of local and regional exposure concentrations the median log KD,SPM value of 5.47 is selected. This value corresponds with a KD,SPMof 295,121 l/kg.

For freshwater sediments, the selected KDvalue was 153,848 L/kg (Log KD: 5.19).

- Estuarine environment:

The next table summarizes the KD,SPM values for suspended particulate matter that were determined in estuarine water bodies. The lowest reported logKD (3.8) was found in a Texan estuary (Benoit et al, 1994). Other values are generally situated between 5.8 and 6.5 with a maximum value of 7.46 (Zhou et al, 2003). However, this value was calculated based on values of suspended particles derived from a graph. Also dissolved Pb was around or beneath detection level, the detection limit was used to calculate the partition coefficient. KD values for this study are thus unreliable estimates. These values were therefore not taken into account while calculating the probability distribution. The maximum value can be found in North Australian estuaries with a KD of 7.2 (Munksgaard and Parry, 2001).

Table: Reported KD,SPM values for Pb is estuarine surface waters.

Location

Log KD(L/kg)

Remarks

Reference

Seine estuary

6.1-6.3

Min-max range

Chiffoleau et al, 1994

Rhine estuary

5.85-6.26

Min-max value

Golimowski et al, 1990

Weser estuary, Germany

5.87-6.27

Different metal extraction methods used

Turner et al, 1992

Mersey estuary, UK

4.7-5.0

Estimated KDfor river water

Turner et al, 2002

Scheldt estuary, Belgium

6.0-6.51

Min-max value

Valenta et al, 1986

Scheldt estuary, Belgium

5.4-6.0

Min-max value

Baeyens, 1998

Penze estuary, France

5.5-6.8

Min-max value

Waeles et al, 2007

Mersey estuary, UK

5.0-5.48

Min-max value with increasing salinity

Hartnett & Berry, 2010

Conway estuary, Wales

5.62-7.46 1

Min-max range

Zhou et al, 2003

S. Baltic Sea

6.67

Median value

Sokolowski et al, 2001

N. Australia

5.5-7.2

Min-max value

Munksgaard and Parry, 2001

Lena estuary, Russia

6.42

Median value

Martin et al, 1993

Texas

3.8-6.8

Min-max value

Benoit et al, 1994

Danshuei estuary, Taiwan

5.2-6.5

Min-max value

Jiann et al, 2005

Nile estuary

5.2-5.3

Min-max value

Abdel-Moati, 1990

RANGE

3.8-7.46

 

 

1 Values were calculated based on reported dissolved and particulate Pb-concentrations

For the calculation of local and regional exposure concentrations in estuarine environments, a median log KD,SPM value of 5.83 should be used. This value corresponds with a KD,SPM of 677,954 L/kg.

- Marine environment:

A median KD,SPM for Pb was calculated for suspended particulate matter in the marine environment, using the data given below. Four reported marine log KD,SPM values were below 5,0 and were representative for the Atlantic Ocean, the Adriatic Sea, the Greek coast near Lesbos and the Scheldt estuary (4.7, 4.8, 4.1 and 4.9, respectively). Log KD,SPM values for the North Sea are situated between 5.0 and 7.25. The maximum value is situated in the Adriatic Sea (log KD,SPMof 7.8). All reported log KD,SPM for other marine water bodies were situated between 5.0 and 7.8.

From a distribution (Triangular) that is fitted through all these data points a median log KD,SPM of 6.18 for Pb in the marine environment is derived. This corresponds with a KD,SPM of 1,518,099 L/kg.   

Table: Reported log KD,SPM values for Pb in marine surface water

Location

Log KD(L/kg)

Remarks

Reference

Belgian coastal waters

5.30-5.60

Min-max range

Baeyens et al, 1987

North Sea coastal waters

5.0-7.0

Min-max range

Balls, 1989

Scottish Sea Loch

6.47

Average value of 3 sampling stations

Hall et al

Southern North Sea

5.9-7.12

Min-max range, NSP-data

McManus and Prandle, 1996

Dover strait

5.712

Summer/winter value

 

Northern North Sea

6.682

Late summer

 

Humber/Wash, UK

6.532

Winter/spring

 

Humber/Wash, UK

7.242

Summer

 

Scheldt, Belgium

4.9

Salinity of 30 ppm

Nolting et al, 1999

Baltic Sea

5.782

6.492

7.102

10thpercentile

50thpercentile

90thpercentile

Pohl and Hennings, 1999

North Sea

5.512

6.302

7.252

10thpercentile

50thpercentile

90thpercentile

Tappin et al, 1995

Seawater, UK

6.2

Modeled value

Tipping et al, 1998

Oceans

6.3-6.5

Min-max range

Valenta at al, 1986

Mytilene, Greek coast

4.1

Calculated value

Angelidis et al, 2003

Adriatic Sea

4.8-7.8

Min-max range

Tankéré et al, 2001

Black Sea

5.9-6.6

Min-max range

Tankéré et al, 2001

Atlantic Ocean

4.7-6.4

Min-max range

Helmers, 1996

RANGE

4.1-7.8

 

 

2Values and/or percentiles were calculated based on reported dissolved and particulate Pb-concentrations

For the marine environment, only one study has reported Pb partition coefficients between the aqueous phase (overlying water) and sediment (Yland et al, 1996). They reported for sediments from the North Sea and Wadden Sea a log KD of 5.66.

 

- Terrestrial environment

 

The best estimates of KDs to assess leaching losses of Pb from the soil are made by models based on in situ pore water concentrations. Adsorption KDs do not take into account ageing reactions while KDs measured in dilute salt extracts tend to underestimate the Pb concentrations in pore water as the ionic strength is usually lower in the extracts than in the pore water. Measurement of Pb concentrations in pore water overcomes these shortcomings. There are only two studies available where KDs are measured based on pore water Pb concentrations (de Groot et al., 1998; Smolders et al., 2000). If the regression models are applied to predict the KD of a “typical” soil with pH 6.5, 2 % organic matter content and 27.4 mg Pb/kg soil, the model of de Groot predicts a KD of 19 103L/kg (Al-ox = 34 mmol kg-1, %fraction 2-38 µm = 12) while the model of Smolders predicts a KD of 1.8 103L/kg. If the pH decreases to 3.5 the KDs decrease to 6.9 10² and 2.2 10² L/kg respectively, if the pH increases to 7.5 the KDs increase to 58 10³ and 3.5 10³ L/kg respectively. It is difficult to derive one “typical” realistic KD based on these two equations. Therefore the average of the median measured KDs (see Table below) by de Groot et al. (1998) and Smolders et al (2000), i.e. 6,400 L/kg, can be used as a realistic KD to calculate Pb leaching losses. A realistic low KD is 6.0 10² L/kg (10th percentile of the combined KD datasets of de Groot and Smolders), a realistic high KD is 43 10³ L/kg (90th percentile of the combined KD datasets).

 

Table: Regression models of KDas a function of soil parameters.

KDregression model

Notes

Reference

logKD= -0.13 + 0.48 pH +0.16 log(%fraction 2-38 µm) + 0.73 log(Al-ox)

r² = 0.84,in situKD, n=47, contaminated and uncontaminated soils from NL, B and D

de Groot et al., 1998

logKD= 0.22 + 0.75 log[Pb]tot+0.30 pH

r² = 0.94,in situKD, n=13, contaminated soils from B

Smolders et al., 2000

logKD= 0.28 pH + log(%OM) + 1.0

r² = 0.38, adsorption KDin 0.005N salts, n=33, contaminated and uncontaminated soils from NL, UK and F

Gerritse & Van Driel, 1984

log[Pb]s= -0.34 – 0.15 pH + 0.61 log(%OM*10)

r² = 0.37, metal concentration in water extract, n=31, contaminated and uncontaminated soils from NL, UK and F

McBride et al., 1997

log[Pb]tot- 0.988 log[Pb]s= 1.30 + 0.55 pH

metal concentration in 0.005 M CaCl2+ 0.005 M Ca(NO3)2extract, n=100, contaminated soils from UK

Jopony & Young, 1994

logKD= 0.37 pH + 0.44 log[Pb]tot+ 1.19

r² = 0.56, compilation of >70 studies, n=204

Sauvé et al., 2000

%OM: percentage organic matter in the soil; [Pb]s: Pb concentration in solution; [Pb]tot: total Pb concentration in the soil, Al-ox: amount of aluminum extracted by ammonium oxalate/oxalic acid, %OC: percentage organic carbon content.

 

The following information is taken into account for any environmental exposure assessment:

From the literature overview, the following partitioning coefficients have been derived for Pb:    

- Aquatic compartment

Partition coefficient in freshwater suspended matter: Kdsusp= 295,121 L/kg

Partition coefficient in freshwater sediment: Kdsed,fw = 153,848 L/kg

Partition coefficient in marine sediment: Kdsed,mar = 457,088 L/kg

Partition coefficient in estuarine suspended matter: Kdsusp= 667,954 L/kg

Partition coefficient in marine suspended matter: Kd,susp= 1,518,099 L/kg

- Soil compartment

Partitioning coefficient: Kd value soil: 6,400 L/kg