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Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

As inorganic compounds, traditional degradation studies are not applicable to ammonium dihydrogenorthophosphate (MAP), diammonium hydrogenorthophosphate (DAP), single superphosphate (SSP) and triple superphosphate (TSP). The degradation pathway is through simple dissociation into phosphates (and sulfates for SSP and TSP) and the corresponding cations (NH4+, Ca2+). In soil and water, nitrification and de-nitrification processes occur as well as in many secondary sewage treatment processes.Due to the water solubility and the ionic nature, the substance is not expected to adsorb or bioaccumulate, water is the main target compartment, and the substance will not volatilize from soil.

Additional information

Phosphates

An additional environmental issue concerning phosphates in general, and therefore also for the abovementioned substances, is their role in the nutrient enrichment of surface waters (eutrophication). MAP, DAP, SSP and STP is 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 a 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).

 

Calcium sulfate

Calcium and sulfate ions are ubiquitous in the environment. Calcium is an important constituent of soil, water and sediment and the minerals found in these compartments are mostly compounds of calcium with other substances. Furthermore, calcium sulfate is known to improve soil quality.

Calcium sulfate is an inorganic substance which does not undergo biodegradation, i.e. microbial degradation to carbon dioxide and water, since it does not contain any carbon or hydrogen atoms. Therefore, the ions will dissociate, calcium will be assimilated by species residing in the soil, water or sediment and is necessary to maintain a good chemical balance in these compartments. The sulfate will become part of the sulfur cycle and/or be assimilated by microorganisms and other species that require sulfate as an essential substance in their biological systems/processes.