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EC number: 231-843-4
CAS number: 7758-94-3
Iron is considered immobile or non-mobile, Log Kd sed 4.997 L/kg dw and log Kd susp 2.34 L/kg dw under environmental conditions (12 °C) are used.Geochemical conditions control the bioavailability as they outreach anthropogenic releases, which are thus unlikely to influence chronic bioavailability due to speciation burying there metals eventually into naturally existing sinks, which represent large reservoirs.
This endpoint is covered by the category approach for soluble iron salts
(please see the section on physical and chemical properties for the
category justification/report format).
It is considered inappropriate to use the Kow and Koc concept for
inorganic compounds as outlined in the waiving argumentation.
Adsorption/desorption as a partitioning process associated with organic
carbon, is not a relevant endpoint for these inorganic salts and
bioavailability is considered the more relevant criterion. Thus a
waiving statement is made.
Nonetheless some information derived from monitoring of water and
corresponding sediment or suspended matter is available and discussed
below. The reported Kd values reflect the total metal concentration
ratio in equilibrium for all species under environmental conditions,
where 12 °C are assumed. It is likely that the data reflect the
environmental speciation behaviour.
In water, there is a rapid formation and deposition of iron oxides
and/or hydroxides, and other salts in sediments. Iron species are
rapidly removed from solution as insoluble precipitate at oxic
conditions and moderate pH. Thus any direct impact of dissolved iron
kations on the aquatic environment will be reduced.
The bioavailability of metals depend more on the geochemical situation
but is characterized by equilibration between the dissolved fraction a
large soil and/or sediment reservoirs making them frequent metals in the
biosphere. Iron is present in all environmental media with large
reservoirs in soils and sediments. Comparison of the environmental
levels with the additional release according to the exposure scenario
shows clearly that the additional releases contribute insignificantly.
Iron partitioning and mobility in soils
Roychoudhury & Starke (2006) examined the partitioning of trace metals
between surface water and sediments and their fate within the sediments
of a river in South Africa in which mine water was drained. A median Log
Kd sed (solids-water in sediment) value of 4.997 L/kg dw for 20
locations with 5th, 10th, and 95th percentile values of 4.687, 4.74, and
5.501 L/kg dw respectively, were reported. The mean Log Kd sed was 5.078
L/kg dw and the values ranged from 4.38 to 5.81. Li (2000) lists a world
average reference value of 6.08 L/kg.
Veselý et al (2001) studied partitioning between solids (suspended
matter) and water by filtration and dialysis in situ in Czech
freshwaters. Field-based distribution (partition) coefficients, Kd,
between suspended particulate matter and filtrate (“dissolved” fraction)
were derived. The median Log Kd susp (solids-water in suspended matter)
for samples from 54 rivers in 119 localities was 2.34 L/kg.
Environmental fate is dominated by abiotic and physico-chemical
processes, including precipitation and settling. Iron reactions in soil
comprise precipitation, hydrolysis, complexation, and redox processes.
The iron released precipitates readily as oxides and hydroxides. Iron
integrates into the mineral structure of soil where it gets buried as it
substitutes for manganese and aluminium in other minerals. Iron often
form complexes with inorganic ligands and occurs mainly in the forms of
oxides and hydroxides either as small particles or in association with
the surfaces of other minerals. Soil iron shows a great affinity to form
mobile organic complexes and chelates which are important compounds
responsible for the migration of iron between soil horizons and the
leaching of iron from soil profiles and also supply of iron to root of
plants (Kabata-Pendias & Pendias 1984, Kerndorff & Schnitzer 1980).
A number of processes influence the iron bioavailability of iron, which
interacts with the bioavailability of other metal species. Significant
adsorption of other metals to iron oxides occurs under environmental
conditions. The process is dependent on pH and is greatest for various
ions at pH 4-5 (Drever 1982, Kabata-Pendias & Pendias 1984, Khalid et al
1977, Windom 1973).:
Concerning data interpretation of the measured Kd in sediments, the
available data clearly indicate that the iron species have to be
considered as “immobile” (Kd or Koc > 5000) or “non-mobile”
(Kd or Koc > 4000) in soils or sediments according to the scales of
McCall et al (1981) or Hollis (1991), respectively. Nonetheless the
sorption to suspended matter is less strong.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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