Trizinc bis(orthophosphate)

Adsorption / desorption

Description of key information

Soil: The median log Kp of 3.24 L/kg dry weight based on experimental results for 498 representative soils for Europe was selected for the partitioning of Zn between solids and water in soil.

Freshwater and marine sediment: The available data show no difference in partitionning of Zn in freshwater or marine sediments.The median log Kp value of 3.49 L/kg dry weight from experimental data for 10 freshwater sediments and 3 marine sediments derived from 9 studies was selected for the partitioning of Zn between solids and water in freshwater and marine sediment.

Freshwater suspended mater: The median log Kp value of 4.67 L/kg dry weight from experimental data for 11 freshwater systems derived from 11 studies was selected for the partitioning of Zn between solids and water in freshwater suspended matter.

Marine suspended mater: The median log Kp value of 4.01 L/kg dry weight from experimental data for 6 marine systems derived from 4 studies was selected for the partitioning of Zn 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:

3.24

at the temperature of:

20 °C

Other adsorption coefficients

Type:

log Kp (solids-water in sediment)

Value in L/kg:

3.49

at the temperature of:

20 °C

Other adsorption coefficients

Type:

other: log Kp (solids-water in marine sediment)

Value in L/kg:

3.49

at the temperature of:

20 °C

Other adsorption coefficients

Type:

log Kp (solids-water in suspended matter)

Value in L/kg:

4.67

at the temperature of:

20 °C

Other adsorption coefficients

Type:

other: log Kp (solids-water in marine suspend matter)

Value in L/kg:

4.01

at the temperature of:

20 °C

Additional information

For metals, adsorption/desorption translates in the distribution of the metals between the different fractions of the environmental compartment, e.g. the water (dissolved fraction, fraction bound to suspended matter), soil (fraction bound or complexed to the soil particles, fraction in the soil pore water,...). This distribution between the different compartments is translated in the partition coefficients between these different fractions. There is substantial reliable (all Klimisch 2) information available for adsorption/desorption of zinc, reporting partitioning coefficients (Kp values, i.e. ratio of Zn concentration in solid phase over dissolved Zn concentration in solution phase) for soil, sediments and suspended matter. Most of the results available for sediment and suspended matter are based on paired monitoring data of elemental Zn concentrations in sediment or suspended matter and water, with some additional studies from Zn spiked suspended matter or sediment. The key information for Kp values in soil is based on batch adsorption experiments with added soluble ZnCl₂ as radioactive spike.

 

Soil

For soil, one key study was selected (Janik et al., 2018). In this study, a subset of 500 spectrally representative soils of a total of 4813 soils of the Geochemical Mapping of Agricultural Soils (GEMAS) program in the EU were sampled (arable land 0 to 20 cm and grassland 0 to 10 cm). Samples were spiked individually with soluble Zn chloride as radioactive spike (Zn 108 kBq Zn(II)). Measurable log Kp values were obtained for 498 soils and range between 0.30 and 4.31 L/kg, with a median logKp value of 3.24 L/kg (Kp: 1737 L/kg). This study is selected over the Buchter (1989) study which was initially considered the key study in the RA Zinc (ECB, 2008) where a log Kp of 2.2 L/kg was derived based on 11 soils. Results summarized in several review documents are largely in the range of the Kp values selected. According to Allison and Allison (2005), 21 log Kp values for soils range from -1.0 to 5.0 L/kg. The median, mean and standard deviation for log Kp, assuming a log-normal distribution, are 3.1, 2.7 and 1.0 L/kg, respectively. In addition, Sauve et al. (2000) summarized 302 log Kp values, including studies using metal-spiked soils, with a min, max and median log Kp of 0.15, 5.51 and 3.24 L/kg, respectively.

The median log Kp of 3.24 L/kg dry weight based on experimental results for 498 representative soils for Europe was selected for the partitioning of Zn between solids and water in soil.

 

Sediment

The information available for Kp values in sediment is based on paired monitoring data of total elemental Zn concentrations in sediment and dissolved Zn concentrations in corresponding pore water or overlying water or on sediments spiked with ZnCl₂ for ecotoxicity testing and appropriate equilibration before measurement of Zn concentrations. For freshwater sediment, 8 studies were identified that report reliable Kp values for Zn in10 sediments from Australia, Belgium, Canada (3), China (2), South- Africa, USA and Vietnam. For each sediment, an average log Kp value was calculated based on all individual data reported. Log Kp values for Zn in sediment of the 10 sediments vary between 2.03 and 5.58 L/kg dry weight, with a median of 3.48 L/kg dry weight. One reliable study was identified for Kp values of Zn in marine sediments, reporting log Kp values ranging from 3.24 to 3.82 L/kg dry weight for 3 marine sediments in the United Kingdom. Results for freshwater and marine sediments did not significantly and were pooled to derive a median log Kp of 3.49 L/kg dry weight for partitioning of Zn between solids and water in freshwater and marine sediment. Values summarized in a review by Allison and Allison (2005) are in the range of the Kp values selected from the experimental studies identified. Reported log Kp values for sediments range from 1.5 to 6.2 L/kg. The median, mean and standard deviation based on a log-normal distribution are 4.8, 4.1 and 1.6 L/kg, respectively.

The median log Kp value of 3.49 L/kg dry weight from experimental data for 10 freshwater sediments and 3 marine sediments derived from 9 studies was selected for the partitioning of Zn between solids and water in freshwater and marine sediment.

 

Suspended matter

All the information available for Kp values in suspended matter is based on paired monitoring data of total elemental Zn concentrations in suspended matter and dissolved Zn concentrations in corresponding water samples or on spiking with radiolabeled ⁶⁵Zn. Reliable data for Kp of Zn in suspended matter was identified for 11 freshwater systems from Canada (3), China (3), Czech Republic, France, Mexico, Morocco and Vietnam. For each freshwater system, an average log Kp value was calculated based on all individual data reported. Log Kp values for Zn in suspended matter for the 11 freshwater systems vary between 3.07 and 5.69 L/kg dry weight, with a median of 4.67 L/kg dry weight. In addition, 4 studies were identified with reliable data for partitioning of Zn in marine suspended matter for 6 locations from China, France and the United Kingdom (4). For each location, an average log Kp value was calculated based on all individual data reported. Partitioning of Zn to suspended matter is generally lower in marine waters compared to freshwater systems. Log Kp values for Zn in suspended matter for the 6 marine systems vary between 3.79 and 4.55 L/kg dry weight, with a median of 4.01 L/kg dry weight. Values summarized in a review by Allison and Allison (2005) are in the same range of the Kp values selected from these experimental studies identified. 47 log Kp values for suspended matter range from 3.5 to 6.9 L/kg. The median, mean and standard deviation assuming a log-normal distribution are 5.1, 5.0 and 0.5 L/kg, respectively.

The median log Kp values of 4.67 and 4.01 L/kg dry weight were selected for the partitioning of Zn between solids and water in freshwater and marine suspended matter, respectively, for the chemical safety assessment.

Summary of key studies for partitioning of Zn:

Medium	Test substance	Log Kp (L/kg)	# data	Reference
Soil
Arable and grazing land soils, Europe	ZnCl2as radioactive spike	3.24 (0.30 – 4.31)	498	Janik et al., 2018
Sediment, freshwater
West Bearskin Lake, Minnesota, USA	ZnCl2	3.12 (2.66 – 3.37)	3	Sibley et al., 1996
Belgium	ZnCl2	3.49 (2.82 – 4.11)	21	Nguyen et al., 2005
Blesbokspruit, South- Africa	Monitoring of elemental Zn concentrations	3.46 (1.51– 4.19)	20	Roychoudhury and Starke, 2006
To Lich and Kim Nguu rivers, Vietnam	Monitoring of elemental Zn concentrations	5.58	1	Marcussen et al., 2008
Lake Erie and Lake Restoule, Canada	Monitoring of elemental Zn concentrations	3.27, 3.47, 3.93	3	Norwood et al., 2008
Warrambucca Creek, NSW, Australia	ZnCl2	4.63 (4.39 – 4.87)	2	Wadige et al., 2014
Hengshi River, China	Monitoring of elemental Zn concentrations	2.03 (2.00–2.05)	2	Liao et al., 2017
Beijiang River, China	Monitoring of elemental Zn concentrations	3.99 (2.89– 4.52)	9	Li et al., 2018
Sediment, marine water
Lake Macquarie, Australia	Monitoring of elemental Zn concentrations	3.24, 3.69, 3.82	3	Galeet al., 2006
Suspended matter, freshwater
Rio Grand, Mexico	Monitoring of elemental Zn concentrations	4.06 (3.43–4.48)	3	Popp and Laquer, 1980
Don River, Canada	Monitoring of elemental Zn concentrations	5.05 (4.34 – 5.54)	10	Warren and Zimmerman, 1994
Czech Rivers	Monitoring of elemental Zn concentrations	4.67	1	Vesely et al., 2001
Fez and Sebou Rivers, Morocco	Monitoring of elemental Zn concentrations	4.24 (3.75 – 4.66)	4	Koukal et al., 2004
St Lawrence river, Canada	Monitoring of elemental Zn concentrations	5.46	1	Gobeil et al., 2005
St Lawrence river, Canada	Monitoring of elemental Zn concentrations	5.69 (5.54 – 6.09)	4	Rondeau et al., 2005
Deule River, France	Monitoring of elemental Zn concentrations	5.05 (4.97 – 5.13)	5	Lesven et al., 2009
Day River, Vietnam	Monitoring of elemental Zn concentrations	5.14 (4.31– 5.55)	10	Duc et al., 2013
Taihu lake,China	Monitoring of elemental Zn concentrations	4.52 (4.13 – 4.72)	6	Zheng et al., 2013
Hengshi River, China	Monitoring of elemental Zn concentrations	3.07 (2.95–3.20)	2	Liao et al., 2017
Beijiang River, China	Monitoring of elemental Zn concentrations	4.56 (4.36– 4.70)	7	Li et al., 2018
Suspended matter, marine water
Seine estuary, France	Monitoring of elemental Zn concentrations	4.55	1	Chiffoleau et al., 1994
Humber Basin, UK	^65Zn	4.03	1	Turner et al., 1993
Clyde, Dee and Tweed, UK	^65Zn	3.79, 3.94, 4.00	3	Turner, 1996
Zhanjiang Bay, China	Monitoring of elemental Zn concentrations	4.26	1	Zhang et al., 2018