Lead dichloride

Adsorption / desorption

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 K_D,SPM values for Pb in European freshwaters.

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⁾K_A: based on the acid soluble concentration

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

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

- Estuarine environment:

The next table summarizes the K_D,SPM values for suspended particulate matter that were determined in estuarine water bodies. The lowest reported logK_D (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. K_D 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 K_D of 7.2 (Munksgaard and Parry, 2001).

Table: Reported K_D,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 K_D,SPM value of 5.83 should be used. This value corresponds with a K_D,SPM of 677,954 L/kg.

- Marine environment:

A median K_D,SPM for Pb was calculated for suspended particulate matter in the marine environment, using the data given below. Four reported marine log K_D,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 K_D,SPM values for the North Sea are situated between 5.0 and 7.25. The maximum value is situated in the Adriatic Sea (log K_D,SPMof 7.8). All reported log K_D,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 K_D,SPM of 6.18 for Pb in the marine environment is derived. This corresponds with a K_D,SPM of 1,518,099 L/kg.   

Table: Reported log K_D,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	5.9-7.1^2	Min-max range, NSP-data	McManus and Prandle, 1996
Dover strait	5.71^2	Summer/winter value
Northern North Sea	6.68^2	Late summer
Humber/Wash, UK	6.53^2	Winter/spring
Humber/Wash, UK	7.24^2	Summer
Scheldt, Belgium	4.9	Salinity of 30 ppm	Nolting et al, 1999
Baltic Sea	5.78^2 6.49^2 7.10^2	10^thpercentile 50^thpercentile 90^thpercentile	Pohl and Hennings, 1999
North Sea	5.51^2 6.30^2 7.25^2	10^thpercentile 50^thpercentile 90^thpercentile	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 K_D of 5.66.

 

- Terrestrial environment

 

The best estimates of K_Ds to assess leaching losses of Pb from the soil are made by models based on in situ pore water concentrations. Adsorption K_Ds do not take into account ageing reactions while K_Ds 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 K_Ds 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 K_D 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 K_D of 19 10³L/kg (Al-ox = 34 mmol kg^-1, %fraction 2-38 µm = 12) while the model of Smolders predicts a K_D of 1.8 10³L/kg. If the pH decreases to 3.5 the K_Ds decrease to 6.9 10² and 2.2 10² L/kg respectively, if the pH increases to 7.5 the K_Ds increase to 58 10³ and 3.5 10³ L/kg respectively. It is difficult to derive one “typical” realistic K_D based on these two equations. Therefore the average of the median measured K_Ds (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 K_D to calculate Pb leaching losses. A realistic low K_D is 6.0 10² L/kg (10^th percentile of the combined K_D datasets of de Groot and Smolders), a realistic high K_D is 43 10³ L/kg (90^th percentile of the combined K_D datasets).

 

Table: Regression models of K_Das 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: Kd_susp= 295,121 L/kg

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

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

Partition coefficient in estuarine suspended matter: Kd_susp= 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