Alkyl-[2-(alkyl-substituted-phosphinoyl)-alkyl]-phosphinic acid

Endpoint summary

Additional information

Hydrolysis

The test item was found to be stable in the preliminary test at pH 4, 7 and 9 at 50 °C. Reaction rate constants and half-lives could not be calculated due to the fact that the test item undergoes no significant hydrolysis. According to the guideline a half-life of > 1 year under environmental conditions can be assumed.

Biodegradation

There is one screening test according OECD Guideline 301 C (readily biodegradation) available. In this test the test item must be regarded to be not readily biodegradable after 28 days. No primary biodegradation / elimination was determined at test end. A second test according the OECD Guideline 302 C (inherent biodegradation) shows the following result. Based on the residue analysis, biodegradation of the test substance was 7.77% in the “test” vessel during the testing period. The BOD results showed that biodegradation of the test substance was 14.7% after 28 days. The test substance has no inherent biodegradation.

Therefore under the test conditions of both studies (OECD 301C and OECD 302C) the pass level was not reached. The test substance is not readily biodegradable and not inherently biodegradable.

Adsorption/Desorption

The highest degree of adsorption (67%) was obtained in eurosoil 5 (KD 8 mL/g. KOC 137 mL/g). This soil is characterized by the highest organic carbon content with 5.96% and sand with 82% as well as the lowest pH value of all tested eurosoils. But the pH value does not have an influence when comparing the results in the used soils because only the monophoshonate is present in the observed pH range of the soils. Adsorption in eurosoil 1 was 56% in equilibrium leading to a KD of 5 mL/g and a KOC of 162 mL/g. This soil is characterised by the highest amount of clay (75%) of all tested eurosoils. The organic carbon content of this soil is 3.27%. Only weak adsorption (approx. 15%) was determined in eurosoil 3. This degree of adsorption resulted in a KD of 0.7 mL/g and a KOC of 23 mL/g. This soil is characterised by an organic carbon content of 3.01%, 17% clay, 37% silt and 46% sand. A decline of adsorption was observed in this soil after 24h of agitation. Therefore values are based on the highest observed adsorption of 15% after 24h of agitation.No adsorption was found in eurosoil 2 and 4.

The results indicate that the amount of organic carbon is of high importance for the adsorption behaviour of the test item when exceeding a certain value. In contrast, no adsorption was observed in eurosoil 2 with an organic carbon content of 3.72%. Furthermore, the amount of clay can be relevant for the adsorption as indicated by high adsorption observed in eurosoil 1. The impact of the other fractions, silt and sand, is only of minor importance. The fact that adsorption is higher in eurosoil 3 (46% sand, 37% silt, 17% clay, 3.01% OC) than in eurosoil 2 (13% sand, 64% silt, 23% clay, 3.72% OC) let assume a more important impact of the sand fraction for the adsorption of the test item in soils. The highest carbon normalized distribution coefficients KOC was obtained for eurosoil 1 though not causing the highest adsorption of the test item. This result demonstrates again that not only a high amount of organic carbon is important for the adsorption behaviour but also a high amount of clay can lead to high adsorption.