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Environmental fate & pathways

Adsorption / desorption

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Description of key information

The sorption characterictics of trisodium nitrilotriacetate (Na3NTA) were determined in studies conducted by Dunlap et al. (1971) and Bolton et al. (1993). The results of both studies clearly indicate that Na3NTA is not strongly adsorbed to soils and sediments. 

Key value for chemical safety assessment

Other adsorption coefficients

Type:
log Kp (sediment-water)
Value in L/kg:
1.6
at the temperature of:
20 °C

Additional information

Trisodium nitrilotriacetate (Na3NTA) is a highly water-soluble organic substance. The aqueous solubility of Na3NTA is 640 g/L. It is also very hydrophilic, judging by its log octanol-water partition coefficient of -13.2 at pH 7.

In addition, a relevant adsorption of Na3NTA onto the oragnic fraction of soils, sediments or suspended solids is not expected due to the ionic structure of the substance. However, interaction with the mineral phase may be possible.

This assumption is supported by the studies conducted by Dunlap et al. (1971) and Bolton et al. (1993). Dunlap et al. (1971) could clearly demonstrate that Na3NTA (-> radiochemical analyses) is not strongly sorbed by loam, clay-loam and sand soils tested. This finding is further supported by the study results of Bolton et al. (1993) who determined the distribution of radiolabeled Na3NTA between a marine surface sediment and a mineral medium. A relatively low distribution coefficient Kp of 1.6 l/kg was determined after 24 h after using sediments that had been stored at 4 °C.

In accordance with the EU RAR (2005) on trisodium nitrilotriacetate, in exposure calculations this value is used for adsoprtion onto sediments, suspended particles and soils.