Reaction mass of Ammonium dihydrogenorthophosphate and diammonium hydrogenorthophosphate.

Endpoint summary

Additional information

As inorganic compounds, traditional degradation studies are not applicable to the reaction mass of ammonium dihydrogenorthophosphate (MAP) and diammonium hydrogenorthophosphate (DAP). The degradation pathway is through simple dissociation into phosphates and the corresponding cations (NH4+). Due to the water solubility and the ionic nature, the substances are not expected to adsorb or bioaccumulate, water is the main target compartment, and the substance will not volatilize from soil.

 

Phosphates

An additional environmental issue concerning phosphates in general, and therefore also for the above mentioned substances, is their role in the nutrient enrichment of surface waters (eutrophication). MAP, DAP, SSP and TSP are hydrolysed in the sewerage pipes, the sewage treatment plants and the environment to soluble inorganic phosphates or transformed to insoluble inorganic forms. These are the same phosphates as those formed by natural hydrolysis of human urine and faeces, animal wastes, food and organic wastes, mineral fertilisers, bacterial recycling of organic materials in ecosystems, etc. These phosphate forms are bio-assimilated by the bacterial populations and the aquatic plants and algae found in these different compartments. Phosphates are an essential nutrient (food element) for plants, and stimulate the growth of water plants

(macrophytes) and/or algae (phytoplankton) if they represent the growth-limiting factor. Although in some cases nutrient enrichment will be absorbed and might not have an apparent effect, in other circumstances, it can lead to negative effects. These can range from ecosystem modifications, through algal blooms, to in extreme cases (through decomposition of plant biomass) oxygen depletion and collapse of the biocenosis in surface water.

As eutrophication is a common effect due to an excess of phosphates in the environment, the problem is covered in European Regulations. The Directive 2000/60/EC of the European parliament and of the council of 23 October 2000 establishing a framework for Community action in the field of water policy is an important European Regulation regulating the emission and concentration of phosphate substances in the environment.

 

De Madariaga BM (2007) developed a conceptual model and protocol for performing European quantitative eutrophication risk assessments of (poly)phosphates in detergents. In this model, the risk probability for eutrophication occurring in the most sensitive areas of a river basin (lakes, reservoirs, meadow zones, estuaries), is based on the TP (total phosphorous) concentration of the inflow water. The variability observed for similar TP concentrations is the consequence of variations in concentrations of N and/or other nutrients, other ecosystem factors and other natural variability. The study also covered the implementation of the model and a set of examples based on generic European scenarios as well as a pan European probabilistic estimation covering the diversity observed for the European conditions and enabled a probabilistic risk assessment of eutrophication relating to the use of STTP in detergents. The scientific validity of this methodology was confirmed by the EU scientific committee SCHER (Opinion of 29th November 2007).

 

Ammonium ion

In soil and water, nitrification and de-nitrification processes occur as well as in many secondary sewage treatment processes.

In aqueous solution, ammonium salts are completely dissociated into NH₄⁺and a corresponding anion. This equilibrium depends on temperature, pH and ionic strength of the water in the environment. Un-ionized NH₃ species exists in the aquatic environments and the fraction (NH₃/( NH₃+ NH₄⁺)) steeply increases with elevated pH value or temperature. The ammonium cation (NH₄⁺) is not an essential ion, but a toxic waste product from animal metabolism that is re-used in protein synthesis via glutamate. Depending on the animal species, ammonium will be directly excreted to the environment or it will first be converted to urea, which is less toxic and can be stored more efficiently. In addition, ammonium is an important source of nitrogen for several plants.