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Environmental fate & pathways

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Due to the ionic structure under environmental relevant pH conditions, no adsorption onto the organic fraction of soils or sediments is expected. An adsorption/desorption screening test is therefore waived. Available data for EDTA and its salts as mentioned in the EU RAR for EDTA (CAS 60 -00 -4, see IUCLID section 13 for read-across justification) is summarized below.

In a laboratory test, the mobility of EDTA in soil was tested. Solutions of EDTA-H4 and ZnEDTA were eluted through cores of two various surface soils. EDTA-H4 was found to be very slightly adsorbed and moved quite readily through both soils. The EDTA from ZnEDTA also moved readily, however, the Zn was replaced by Fe to a large extent (Cheng et al., 1972).

The influence of EDTA on the sorption of Zn onto soils was tested by Elrashidi and O'Connor (1982). The presence of EDTA in the soil suspension significantly decreased the Zn sorption on 3 investigated soils. Only a slight difference in Zn sorption was observed whether EDTA was added to the Zn containing soil before or after contact with soil.

Similar effects were found with Cd, the adsorption is significantly reduced (Elliott and Denneny, 1982; Fuji, 1978).

A model calculation of the distribution of EDTA metal complexes between water and suspended solids resulted that <1% of the total EDTA is adsorbed. The parameters should be valid for the Swiss river Glatt: with an EDTA concentration 30 μg/l and a suspended matter concentration of 10 mg/l, only EDTA metal complexes can adsorb (Kari, 1994).

In an experiment, the distribution between water and sediment of the Swiss river Glatt was estimated for 3 different EDTA metal complexes. The EDTA concentration was measured in the water phase, from this the partition coefficients were calculated: 3 l.kg-1 for CaEDTA, 38 l.kg-1 for ZnEDTA, and 113 l.kg-1 for CuEDTA. For the real conditions of the river Glatt, the adsorbed part of the total EDTA content should generally range below 0.1% (Kari, 1994).

For the exposure calculation, values for Kpsoil, Kpsed and Kpsusp of 75 l.kg-1 are used. This is the average value between Zn- and CuEDTA, CaEDTA is not expected in most surface waters (see Section 3.1.3.3).

Based on the physico-chemical properties of EDTA-H4, a calculation with the fugacity model Mackay level I predicts that the hydrosphere is the preferred environmental compartment (99.999%).