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EC number: 948-652-3
CAS number: -
SoilThe results of the GEMAS survey (Janik et al. 2010) are used to derive the Kd value for soil. 497 Kd values for silver were measured in agricultural soils sampled from throughout Europe. The median value is log Kd 3.60 (Kd 4023), 10th and 90th values percentile are log Kd 3.08 and >3.67 (Kd 1200 and >4,700). The value of 4,700 is the upper limit of detection and so is both the maximum value and 90th percentile.Suspended sedimentThe selected value, the mean of four log Kd values reported from separate studies, is log Kd 5.28 (Kd 190546).SedimentThe selected value, the mean of two log Kd values reported from separate studies, is log Kd 4.05 (Kd 11092).STPThe partitioning of silver in an STP is expressed in terms of the fraction of influent silver in the final effluent (0.199) and the sludge (0.801). The fraction partitioning to sludge is derived as the geometric mean of 14 measurements reported from three separate studies.
of metals between aqueous phase and soil/sediment/suspended matter
should be described on the basis of measured soil/water, sediment/water
and suspended matter/water equilibrium partition coefficients (Kd),
instead of using common mathematical relationships based on, for
example, octanol-water partition coefficients, as is usually done for
organic chemicals (TGD, 1996).
order to reduce the influence of a particular study or sampling site
where a large number of Kd determinations have been made, often within a
limited geographic area, a single Kd value was identified for each
individual study. In some cases where Kd values (or the data from which
they could be calculated) were not stated explicitly in the studies
these values were estimated from graphs: in these cases, the selected
values are used as supporting information only. In other cases, the
values were calculated as the mean log Kd value across sampling sites in
the study. Mean values are calculated where log transformed Kd values
are reported: where Kd values (not log transformed) are summarised the
median value is used. In cases where multiple determinations of Kd were
made at each sampling site, the mean log10 Kd value for each individual
site was used as the input for the overall log Kd calculation. A
distribution of Kd values is therefore derived for each partitioning
phase (suspended sediment, settled sediment), with equal weighting
attributed to each study. For soils, the results of a single large
European study are used.
Kd values for soil were derived from partition coefficient information
collected within the GEMAS project (Janik et al. 2010). This project
used agricultural soils collected from throughout Europe and is a
consistent and comprehensive study of silver partitioning in European
soils. A weight of evidence approach has been taken to determine the log
Kd values for soil, suspended matter and sediment. Available data on the
partitioning of silver in the environment show that a wide range of
partition coefficients are observed, depending upon the local
conditions. The values for the partition coefficients used in the
assessment are median values based on measured data.
log Kd values that will be used in the assessment are: log Kd soil 3.60
(Kd 4023), log Kd suspended matter 5.28 (Kd 190546) and log Kd sediment
4.05 (Kd 11092).
partitioning of silver during sewage treatment has also been addressed
empirically based on measured data in STP influent and effluent from
several studies. Due to the extremely low volatility of silver, and the
fact that it cannot be degraded, all silver which is removed from
wastewater is assumed to be partitioned to the sewage sludge. The
partitioning of silver in STP is based on the geometric mean of
measurements reported for 14 separate STPs in three separate studies and
is expressed as the fraction of influent silver in the final effluent
(0.199) and the sludge (0.801) – removal efficiency of 80.1 %. Mean and
median removal efficiencies were 82.9 and 87.5, respectively.
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