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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

Three reliable simulation studies of ATMP-H in water and sediment systems are available. Low but recordable levels of removal are seen in such systems, particularly in the presence of natural or simulated light.

Although biodegradation in sediment has not been demonstrated for ATMP-H and its salts, the role of abiotic removal processes is significant. The key data for soil adsorption are from the study by Michael (undated). There is no evidence for desorption occurring. Effectively irreversible binding is entirely consistent with the known behaviour of complexation and binding within crystal lattices. The high levels of adsorption which occur are therefore a form of removal from the environment. After approximately 40-50 days, the phosphonate is >95% bound to sediment with only 5% extractable by ultrasonication and use of 0.25N HCl-xylene solvent (based on radiolabelling) in river and lake water microcosms. (Monsanto internal report, cited by Gledhill and Feijtel, 1992). 66-80% removal (binding) is seen after 11 days in the same test. In the context of the exposure assessment, largely irreversible binding is interpreted as a removal process; 5% remaining after 40 - 50 days is equivalent to a half-life of 10 days which is significant for the environmental exposure assessment in the regional and continental scales. This abiotic removal rate is used in the chemical safety assessment of ATMP-H and its salts.

Key value for chemical safety assessment

Half-life in freshwater:
10 d
at the temperature of:
25 °C
Half-life in freshwater sediment:
10 d
at the temperature of:
25 °C

Additional information

Reliable data are available for degradation in natural freshwaters and marine waters. Minimal degradation is indicated:

Biodegradation in a water-sediment microcosm of 5 - 12 % after 28 days (1 - 5% under anaerobic conditions) was determined (Saeger 1979).

Biodegradation in river and lake waters of ca. 10 - 15% after 60 days was determined (Saeger 1978).

Biodegradation in seawater of -2% in 28 days (Drake 2005) 2.6% to 21.7% in 28 days (Rowlands 2005), 22% to 41% in 28d (Hamwijk and Cremers 2005), and 8 -11% (28 days) and 18 -23% (56 days) (Muttzall and Hanstveit 1996) were determined.