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EC number: 231-850-2
CAS number: 7759-02-6
Partition coefficients for different environmental compartments (sediment, suspended particulate matter, soil) have been derived for strontium, based on literature data and on data generation in the FOREGS monitoring survey.- The value for soil is the geometric mean of three data points, and is 157.03 L/kg (logKD 2.20)- For the sediment compartment the typical KD based on FOREGS data is put forward as a reliable value for Europe, i. e., 861.2 L/kg (logKD 2.94).- A value of 1.5 has been proposed as a relevant ratio between the Kd for sediment and the KD for suspended particulate matter (Stortelder et al, 1989; Van de Meent et al, 1990), and this ratio was also used by RIVM for setting relevant Kd-values for various metals. Application of this factor on the KD, sediment of 861.2 L/kg, results in an estimated Kd, suspended mater of 1,291.8 L/kg (logKD 3.11).
In the aqueous
and terrestrial environment, strontium sulfate dissolves in (pore) water
releasing strontium cations and sulfate anions. Sulfate is essential to
all living organisms, their intracellular and extracellular
concentrations are actively regulated and thus, sulfates are of low
toxicity to the environment (OECD SIDS for Na2SO4). Thus, the strontium
cation is the moiety of toxicological concern (if any), and the
environmental hazard assessment is based on strontium.
The derivation of
environmental fate data like adsorption/desorption coefficients and
bioconcentration / bioaccumulation factors is based on measured
strontium levels, and reflect the properties of the dissolved strontium
cation. The latter form is the only form under which dissolved strontium
originating from a simple inorganic strontium compound will occur.
Therefore the reported elemental-based environmental fate data in this
section of the dossier are considered relevant for the behaviour of
strontium that is released into the environment from strontium sulfate.
literature values reporting KD-values for strontium in sediment were
identified, and ranged from 27 to 117.4 L/kg (see table below). These
values were used for the determination of a typical Sr-KD-value for the
sediment compartment. The geometric mean of the reported KD values was
applied to derive this typical sediment KD since all the reported data
are considered to be of equal quality, and a KD value of 40.04 L/kg was
obtained. The sediments used in the reviewed studies were mainly sandy
sediments. The weaker strontium sorption by sand compared to clay, silt
or organic matter results in a relatively low KD value.
Overview of partition coefficient between the water and sediment
Bunde et al (1997)
31.5 (log KD: 1.50)
Bunde et al (1998)
58.36 (log KD: 1.77)
Hemming et al (1997)
17.67 (log KD: 1.25)
Kaplan et al (2000)
27 (log KD: 1.43)
Liszewski et al (2000)
117.40 (log KD: 2.07)
40.04 (log KD: 1.60)
In a further
study, the partition coefficient of water and marine sediment was
calculated (Caroll et al, 1999), and a KD for the marine sediment of
75.76 L/kg (log KD: 1.88) was determined using the data of the study.
Geochemical Baseline Mapping Programs main aim was to provide high
quality, multi-purpose environmental geochemical baseline data for
Europe. The sampling sites selected for stream water analyses of
dissolved metals were typical of locally unimpacted or slightly impacted
areas. Consequently, the metal concentrations that are determined in
these samples can be considered as relevant baseline concentrations. A
total number of 808 water samples were analyzed for strontium by ICP-OES
(detection limit 1 µg/L); dissolved strontium levels ranged between 1
and 13,600 µg/L. For the sediment compartment, the amount of analyzed
samples was 852, with strontium levels ranging between 31 mg/kg and
1,3522 mg/kg dw. Sediment samples were analyzed by ICP-XRF (X-ray
fluorescence; detection limit of 1 mg/kg dw). Raw data were
sub-categorized per country, and a typical baseline value (i. e., 50thpercentile
or median) of strontium in water and sediment were determined for each
country, respectively. Assuming that the country-specific median values
are relevant for both compartments and represent a state of chemical
equilibrium, a typical Kd-value can be derived for each country. Typical
country-specific log KD values range from 2.57 to 4.35, with an overall
median value of 2.94 for Europe (i. e., 861.2 L/kg).
literature review and data analysis on strontium partitioning
coefficients for the sediment compartment also resulted in some
KD-values that were more relevant for soil particles. The geometric mean
of the reported KD values was taken to derive a typical soil KD since
all the reported data are considered to be of equal quality. As such a
KD value of 157.03 L/kg is obtained.
The table below
gives an overview of the different relevant KD-values that were selected
for the derivation of a typical soil-partition coefficient.
Overview of partition coefficient between the water and soil compartment
Bunzl and Schimmack (1989) - E-horizon
44 (log KD: 1.64)
Kami-Ishikawa and Tagami (2008) upland soil
220 (log KD: 2.34 )
400 (log KD: 2.60)
157.03 (log KD: 2.20)
For the sediment
compartment, two values were identified, i. e., a literature value of
40.04 L/kg based on a limited data set (n=5) and the value of 861.2 L/Kg
which was derived for with the data generated in the FOREGS monitoring
survey (Salminen et al, 2005).
The latter value
was put forward as a typical value for the sediment compartment:
literature data were primarily relevant for sandy soils which have a low
affinity for metals due to their low clay and organic matter content;
therefore they are not representative for silty, loamy and clayey soils.
represents a large amount of samples (>800) representing the whole of
Europe; and strontium levels in water and sediment were determined in a
Based on the data
provided inCrommentuyn et al (1997)it can be concluded that the
sediment KD of cationic metals (e. g., Ba, Be, Cd, Co, Cu, Pb, Ni, Zn)
is always at least one order of magnitude higher than the soil KD, with
differences up to 3 orders of magnitude. Taking into account that
literature KD-values for soil were situated between 44 and 400 L/kg, a
sediment KD of 40.04 L/kg (based on literature data) would be unlikely.
No data were
identified for particulate suspended matter. A partition coefficient for
this compartment, however, can be estimated, based on the partition
coefficient for sediment which is increased by a factor of 1.5 (Stortelder
et al, 1989; Van de Meent et al, 1990) to account for the weaker
adsorption of sediments as compared to particulate matter (DBW/RIZA,
1989): the relatively strong adsorption of metals by particulate
matter is probably related to the relatively high organic matter and
clay content (size fraction < 2 µm).Bockting et al (1992)
indicated that this factor of 1.5 remains an assumption and use of this
value should be dome with caution.
According to this
methodology, a KD, spm of 1291.8 L/kg (i. e., log KD, spm of 3.11) is
derived for this compartment.
For the soil
compartment the geometric mean of three literature data points is put
forward as a typical value for the Sr-KD for soil, i. e., 157.03 L/kg
(log KD: 2.20)
of the KD-values for the different environmental compartments is given
Salminen et al (2005; FOREGS data)
Suspended particulate matter
Estimated data (ratio of 1.5 on KD,sediment)
Crommentuyn et al (1997)
T, et al. (1997): Maximum permissible concentrations and negligible
concentrations for metals, taking background concentrations into
account. RIVM Report No. 601501001.
P.B.M., et al. (1989). Perspectives for water organisms (part 1 and 2)
DBW/RIZA Nota No. 89.016a+b, Lelystad, The Netherlands.
de Meent, D. et al. (1990):Objective
Quality. Background study as a support for the regulatory report on
'Environmental Quality Objectives for Water and Soil, RIVM
G.J.M., et al. (1992): Soil-water partition coefficients for some trace
metals, national institute of public health and environmental
protection, report no. 679101003, Bilthoven, The Netherlands, pp. 51
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