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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Adsorption/desorption is not relevant for aluminium nitride.

Key value for chemical safety assessment

Additional information

According to Annex VIII section 9.3.1 and Annex IX section 9.3.3, column 2 of the REACH Regulation an adsorption/desorption study does not need to be conducted if the substance has a low potential for adsorption. Whereas this criterion is not applicable to aluminium nitride, the endpoints 9.3.1 "Adsorption/desorption screening" and 9.3.3 "Further information on adsorption/desorption" are waived for the following reasons:

Aluminium is part of the natural soil matrix and it is the most abundant metallic element, comprising 8 % of the earth crust. It is a major component of almost all common inorganic soil particles. Dissolved aluminium is present in soil pore water at very low concentrations, varying with pH. This is common textbook knowledge, not requiring further elaboration.

In view of the high abundance of aluminium in soil, predominantly bound to the mineral matrix, the contribution of any environmental releases of aluminium nitride to the aluminium exchange equilibrium hence to the concentration and availability of the element in soil is expected to be insignificant. Therefore, detailed information on adsorption and desorption of aluminium would not make a significant contribution to the chemical safety assessment and is therefore not required.

Ammonia is formed as an important product of hydrolysis upon contact of aluminium nitride with water (e.g. soil pore water). In soil, ammonia can undergo sequential transformation by two processes in the nitrogen cycle: nitrification and denitrification. By these processes ammonia is transformed into nitrite (NO2–), nitrate (NO3–), and elemental nitrogen, and therefore becomes part of the global nitrogen cycle. This is common textbook knowledge and does not require further elaboration.

Despite being an important breakdown product the total amount of ammonia formed by hydrolysis of aluminium nitride is insignificant (see transformation/dissolution test, IUCLID sections 4.8 and 5.1.2), compared to the quantities formed by any biological processes in the nitrogen cycle, be it on a local, regional or global scale, not resulting in any environmental hazards.