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Ecotoxicological information

Toxicity to soil macroorganisms except arthropods

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Studies performed on earthworms using a hydrated salt of aluminium sulphate (and aluminium chloride hexahydrate) in addition to the standard soil containing kaolinite (Al2Si205(OH)) resulted in ecotoxicity at concentrations considerably lower than those found in top- and sub-soils (14 d LC50s around 300 mgAl/Kg dw at pH 3-4 and >1000 mgAl/Kg dw at pH4-6 and 6 week NOECs of 100 mg Al/Kg dw at pH 3.4 -7.3 for reproduction). The observed toxicity could not be related to extractible aluminium concentration as there was no difference between aluminium concentrations extracted from controls and treatments at pH 7.3. There were certain differences between treatment levels such as the addition of CaCO3 which was used to attenuate low soil pH further to aluminium treatment. It is therefore not clear whether the effects found can be directly attributed to aluminium toxicity.

Aluminium, its powders and salts are not classified for the environment. Under normal environmental conditions they are non-hazardous and may only become so when found in conjunction with physicochemical parameters at the extremes limits of aquatic environmental habitats (for example, pH below 6 together with very low DOC). Aluminum (Al) is the most commonly occurring metallic element, comprising eight percent of the earth's crust (Press and Siever, 1974) and is therefore found in great abundance in both the terrestrial and sediment environments. Concentrations of 3 -8% (30,000-80,000 ppm as Al) are common. In a European wide survey by FOREGS (2006) the 50th percentile concentration of aluminium oxide in topsoil is 11% with approximately 1% of European topsoils containing less than 2% aluminium oxide. Thus large quantities must be ingested by terrestrial invertebrates (notably soil burrowers such as earthworms) without ecological consequences. The relative contributions of anthropogenic aluminium compared to the existing natural pools of aluminium in soils and sediments is very small and therefore not relevant either in terms of added amounts or in terms of toxicity. Based on these exposure considerations additional sediment and/or soil testing is not warranted. Summary table of results on earthworm toxicity studies

species

endpoint

set up

pH(KCl)

result (mg/kg dw)

 

Aluminum chloride

Eisenia andrei

LC50-14d

Artificial soil

3.3

4.4

6.7

316

359

>1000

 Al

Sulfuric acid, aluminium salt (3:2), octadecahydrate (CAS RN 7784-31-8)

)

Eisenia andrei

LC50-14d

Artificial soil

3.3

4.4

6.7

457

>4000

>4000

Al

Eisenia andrei

NOEC-42d

Artificial soil

3.4

100

Al