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Aluminium dihydrogen triphosphate (CAS 13939-25-8) is an inorganic aluminium phosphate salt comprising three phosphate units. The substance does not undergo biological degradation. Aluminium and phosphorus are both natural elements, which are present in all environmental compartments. Aluminium dihydrogen triphosphate (CAS 13939-25-8) will be removed from the water column by hydrolytic transformation or by chemical precipitation. The precipitates of aluminium and phosphorus will be further transformed in soil and sediment systems by mineralisation. 

The complex environmental chemistry of aluminium is addressed in several reports and public available sources to date (ATSDR (2008), Environment Agency (2007), Environment Canada and Health Canada (2000), RIZA (2002), WHO (2010)). Aluminium is the third most abundant element of the earth's crust. Aluminium enters the environment from anthropogenic sources such as drinking water and wastewater treatment. But the release from natural sources such as weathering of rocks and volcanic activity is usually dominant. The phosphorus and phosphate anions are ubiquitous in natural waters and essential micronutrient for many organisms.

Bioaccumulation and secondary poisoning are not considered significant for aluminium dihydrogen triphosphate (CAS 13939-25-8). Aluminium dihydrogen triphosphate is not expected to bioaccumulate in organisms and food chains. In a GLP guideline study following OECD 305 a BCF ≤ 43 was determined. An accumulation of phosphate in organisms is unlikely to pose a hazard potential, as the phosphate anion is an essential micronutrient for many organisms and the internal concentration is regulated biologically.

The relative mobility of aluminium species depends upon on many factors, especially pH, alkalinity, temperature, dissolved organic carbon, and anion concentration. At low pH (less than 5.5), aluminium is present is the predominant as Al3+ species, which is highly mobile. As pH increases above 5.5, aluminium-hydroxide complexes and organically complexed aluminium will be formed either by hydrolysis or by combination with organic matter. Above pH 7, anionic aluminium hydroxide predominates. Kaplan (2005) published several Kd values based on measured Al concentration in groundwater and sediment and suggested Al Kd values for soil, grout, gravel, clay to be 3700 mL/g and 5000 mL/g for concrete, respectively. Furthermore, aluminium species play itself also an important role in the adsorption of other trace metal or anions in soils and sediments. Furthermore, colloidal aluminium species play also an important role in the adsorption of other trace metals and anions in soils and sediments.

Phosphorus retention in soils is influenced by the form of P released. Triphosphate is a condensed phosphorus species with three phosphate units. Busman (1984) studied the adsorption of polyphosphate by soils and clay minerals and indicated that affinity of polyphosphate increased with increasing length of phosphate units. Triphosphate was more strongly adsorbed than orthophosphate, whereas mobility and solubility of triphosphate increased by hydrolysis in soils to orthophosphate.

The air compartment is considered not relevant for aluminium dihydrogen triphosphate. Due to its physico-chemical properties, aluminium dihydrogen triphosphate is not distributed or transported to the atmosphere as the substance is usually not emitted to air. The amount of aluminium contributed by the considered substance to the total aluminium present in air would be negligible compared with the amount of aluminium coming from natural erosion of soil (Environment Canada Health Canada, 2000).

In aquatic systems, aluminium can be present in  different forms which are complexed from dissolved species with free aluminium ions (Al3+) to high molecular mass species such as colloids or particles, as well as complexes with naturally occurring organic substances , such as humic and fulvic acids. Aluminium concentrations in most freshwaters are generally low due to the low solubility of aluminium species at typical aquatic environmental pH between 5 and 8. Outside this pH range, solubility increases markedly.

Triphosphate species can be hydrolysed forming orthophosphate (PO43-) in sewerage systems, sewage treatment plants and in the environment. These same orthophosphates are also 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. Phosphates are bio-assimilated by the bacterial populations and the aquatic plants and algae found in these different compartments and 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.

Affinity of aluminium is highly dependent on pH and geochemical properties of soils where mobility is higher at low pH. 

References:

ATSDR (Agency for Toxic Substances and Disease Registry) (2008). Toxicological Profile for Aluminum. Atlanta,: Department of Health and Human Services, Public Health Service.

Busman, Lowell Marion, "Behavior of polyphosphates in soils " (1984). Retrospective Theses and Dissertations. Paper 8979.

Canada. (2000). Canadian Environmental Protection Act: Persistence and Bioaccumulation Regulations, P.C. 2000-348, 23 March, 2000, SOR/2000-107, Canada Gazette. Part II, vol. 134, no. 7, p. 607−612. Available from: http://canadagazette.gc.ca/partII/2000/20000329/pdf/g2-13407.pdf

Council Directive 91/271/EEC of 21 May 1991 concerning urban waste-water treatment

Directive 2000/60/EC of the European Parliament and of the Council establishing a framework for the Community action in the field of water policy

Environment Agency (2007) Proposed EQS for Water Framework Directive Annex VIII, Substances: aluminium (inorganic monometric), Science Report: SC040038/SR1; SNIFER Report: WFD52 (i); ISBN: 978 -1 -84432 -651 -8, Feb 2007

Kaplan D.I. (2005) Recommended Distribution Coefficients, Kd Values, for Special Analysis Risk Calculations Related to Waste Disposal and Tank Closure on the Savannah River Site (U), Westinghouse Savannah River Company Savannah River Site,

RIZA (2002), Een ad-hoc Maximaal Toelaatbaar Risiconiveau (MTR) voor aluminium in oppervlaktewater, , 4L1574.A1/R0001/EVDP/Nijm, 26 april 2002

WHO (2010), Aluminium in drinking-water. Background document for development of WHO Guidelines for Drinking-water Quality. Geneva, World Health Organization (WHO/HSE/WSH/10.01/13)).

WHO (1997). Environmental Health Criteria 194. Aluminum. International Programme on Chemical Safety (IPCS). Geneva ISBN 92 4 157194 2.