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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Adsorption to solid soil phase is not expected for the organic component of the test substance (estimated Koc:  1 L/kg, log Koc: 0).
Adsorption to solid particulate matter is expected fort the zinc ion (Kpsusp: 110000 L/kg; corresponding log value: 5.04).
Adsorption to solid sediment phase is expected for the zinc ion (Kpsed: 73000 L/kg; corresponding log value: 4.86)
Adsorption in marine waters is expected for the zinc ion (6010 L/kg; log value: 3.78).
Adsorption to soild soil phase is possible for the zinc ion (158.5 L/kg; log value: 2.2)

Key value for chemical safety assessment

Additional information

For the organometallic test substance no studies on the adsorption potential are available. Since the test substance is a reaction product of zinc oxid (CAS 1314-13-2) and glycerol (CAS 56-81-5), the adsorption potential of the test substance was estimated based on the adsorption behaviour of these two parent compounds.

 

Adsorption potential of glycerol:

As calculated using SRC PCKOCWIN v2.00, the Koc of gylcerol (CAS 56-81-5) is 1 L/kg [BASF, 2011a].

 

Adsorption potential of the zinc ion:

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. Study records on partition coefficients are given under 5.6.

Partition coefficients for zinc in freshwater has been reviewed in the RAR (ECB 2008). Based on the extensive experimental evidence, a partition coefficient for the distribution between solid particulate matter and water (Kpsusp) of 5.04 (log value) has been defined for EU waters and used throughout the RAR.

The Kp for the distribution between sediment and water (Kpsed) was estimated in the RAR from that for particulate matter, as follows: Kpsed= Kpsusp/ 1.5, based on the average difference in concentrations of zinc and other metals in both media. For zinc this results in a Kpsed of 73,000 L/kg. (ECB 2008)

The marine Kd was derived based on data from several marine waters. the geomean value for zinc in seawater is 6010 L/kg

For soil, a solids-water partitioning coefficient of 158.5 l/kg (log value 2.2) was determined experimentally on 11 American soils. This value was used in the RA Zinc.