Aluminium ammonium bis(sulphate)

Endpoint summary

Additional information

Aluminium ammonium sulfate is highly soluble and will form various dissolved species on contact with water: its two component salts, aluminium sulfate and ammonium sulfate, and further completely to SO4 2-; NH4+ and Al3+ ions.

 

Aluminium

As aluminium is the third most common element in the earth’s crust, the literature is voluminous and the reviews that have been used in the compilation of this submission are the most recent and are listed below.

- ATSDR (2008). Agency for Toxic Substances and Disease Registry. Toxicological profile for aluminium. September 2008.

- Environment Canada and Health Canada (2010). Priority Substances List Assessment Report for Aluminium chloride, Aluminium nitrate and Aluminium sulphate, January 2010.

- Kaplan DI (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 Aiken, SC 29808; Prepared for the U.S. Department of Energy Under Contract Number DE-AC09-96SR18500

- WHO (1997). Environmental Health Criteria 194. United Nations Environment Programme, International Labour Organisation, World Health Organization, International Programme On Chemical Safety.

 

The transport and partitioning of aluminum in the environment is determined by its chemical properties, as well as the characteristics of the environmental matrix that affect its solubility.

At a pH >5.5, naturally occurring aluminum compounds exist predominantly in an undissolved form such as gibbsite, Al(OH)3, or as aluminosilicates except in the presence of high amounts of dissolved organic material or fulvic acid, which binds with aluminum and can cause increased dissolved aluminum concentrations in streams and lakes. In general, decreasing pH (acidification) results in an increase in mobility for monomeric forms of aluminum, which is of concern with respect to the occurrence of acid rain and the release of acid mine drainage. In contrast, in areas not affected by acidification, aluminum in solution was partitioned between labile and non-labile forms, the latter being predominantly bound to fluorine. In soils, the most soluble form of aluminum under acidic conditions is nonsilicaceous, organically-bound aluminum.

In groundwater or surface water systems, equilibrium with a solid phase form is established that largely controls the extent of aluminum dissolution which can occur. In acid sulfate waters resulting frommine drainage, gibbsite and kaolinite are not stable, and the solubility of the minerals jurbanite (Al(SO₄)(OH)·H₂O) or alunite (KAl₃(SO₄)₂(OH)₆) may control aluminum levels. In addition to the effect of pH on mobility, the type of acid entering environmental systems may also be important. 

The adsorption of aluminum onto clay surfaces can be a significant factor in controlling aluminum mobility in the environment, and these adsorption reactions, measured in one study at pH 3.0 – 4.1, have been observed to be very rapid. However, clays may act either as a sink or a source for soluble aluminum depending on the degree of aluminum saturation on the clay surface. Kaplan (2005) published several Kd values based on measured groundwater and sediment concentrations. For sandy soils / sediment the value of 3700 L/kg was established as representative.

The presence of high levels of suspended solids in stream surface water during storm episodes resulted in higher concentrations of adsorbed aluminum than in the absence of suspended solids. The increased adsorption was not strictly linear, with higher concentrations of suspended solids due to variations in the particle size distribution and the nature of the particles.

Within the pH range of 5–6, aluminum complexes with phosphate and is removed from solution.

Aluminum, as a constituent of soil, weathered rock, and solid waste from industrial processes, is transported through the atmosphere as windblown particulate matter and is deposited onto land and water by wet and dry deposition. Atmospheric loading rates of aluminum to Lake Michigan were estimated at 5 million kg/year. In this study, most of the aluminum was generally associated with large particles that were deposited near their source.

Ammonium sulfate

The SIDS Initial Assessment Report (OECD SIDS, 2004) reports the transport and distribution of ammonium sulfate.

Ammonium salts and sulfates are abundant in the environment. Approximately 90 % of ammonium sulfate is used in products applied directly to land, for example as fertilisers or as a component in herbicides.

Due to the salt-character of the substance the calculation of a fugacity model and Henrys Law Constant is not appropriate. Based on the physico-chemical properties of ammonium sulfate, water is expected to be the main target compartment. Although ammonium sulfate can be created in the atmosphere from ammonia and sulfur dioxide, this process is limited by atmospheric sulfur dioxide, not by ammonia, which has many natural sources. Particulate ammonium sulfate is removed from air by wet and dry deposition. There is no evidence for photodegradation of ammonium sulfate. In unsterilized soil, ammonium sulfate is mineralized fairly rapidly, and subsequently nitrified. Nitrification and denitrification processes also occur naturally in streams and rivers, as well as in many secondary sewage treatment processes.

Based on the high water solubility and the ionic nature, ammonium sulfate is not expected to adsorb or bioaccumulate to a significant extent. However, mobility in soil may be reduced through ion-ion interactions.