Amelioration of aluminium toxicity in Atlantic salmon, Salmo salar L., with particular reference to aluminium/silicon interactions

Abstract

The aim of the research was to examine amelioration strategies for aluminium and in particular the potential of silicon to ameliorate the acute toxicity of A1 in Atlantic Salmo salar, fry in a dilute acid water. Methods were developed for the analysis of A1 and Si using graphite furnace atomic absorption spectrometry. This technique was then combined with carefully defined pre-treatment procedures to investigate simple A1 speciation and solubility in dilute aqueous milieu. Research than examined the potential of Ca(OH)2(s)CaCO3(s) and CaO/SiO2(2)to ameliorate acute A1 toxicity. A field study highlighted the inadequacies of Ca (OH)(2)(s)as an effective agent to ameliorate A1 toxicity and laboratory studies, whilst substantiating these inadequacies for both Ca(0H)2(s) and CaCO3(s) highlighted the potential of Ca0/Si02(s), and in particular silicic acid, as a potential detoxification agent for A1 in acid waters. Detailed laboratory studios of the interactions between A1 and silicic acid in dilute aqueous environments demonstrated the formation of aluminosilicates, the stabilities of which were dependent on the pH and the silicic acid concentration. Stable, occasionally charged aluminosilicate species were formed at silicic acid concentrations above 1000/ugl-1 probably through the interaction of silicic acid with the aluminate anion. Al(OH)4(aq) Those species were slow to come out of solution and increased Al solubility with respect to amorphous in the short-term, (168h). A flow-through toxicity system was developed to assess the results of these Al/Si interactions on the acute toxicity of Al to Atlantic salmon fry at pH 5.0. Acute Al toxicity was found to be abolished by a critical concentration of silicic acid, (•* 7S0^X^ "2400 /ugl~^). The silicic acid rendered the Al biologically unavailable, Al neither being taken up by the fish nor associating with the gill surface, and this observation has outlined a potential and not previously considered role of silicon in biology.