Ecological Systems and Devices Annotation << Back EFFECT OF MEDIUM PH ON THE ALUMINUM TOXICITY TO MICROALGAE M.A. Mikheev, V.I. Ipatova Hydrogen index (pH) is one of the important environmental factors regulating the growth and reproduction of algae in natural conditions and cultures. The effect of the initial pH of the medium on the toxicity of aluminum chloride to the culture of the alga Scenedesmus quadricauda (Thurp.) Breb., widely used in bioassay as a test object, was investigated. The toxicity of aluminum chloride is highly dependent on the pH of the medium. Low and medium concentrations (0,4…50 mg/l) of the toxicant do not significantly change the initial pH of the medium, and high concentrations (100 mg/l and more) lead to acidifi cation. Under artifi cial acidification of the medium from pH 7,2 to 5,2 at the beginning of the experiment, the concentration of 0,04 mg Al3+/l, corresponding to the MPC of aluminum in the water bodies, becomes toxic to S. quadricauda, and the toxicity of higher concentrations 1 and 10 mg/l of aluminum chloride increases. Artificial alkalinization of the medium, changing the pH from 4,39 to 7,2, completely removes the toxicity of a high concentration of 100 mg/l AlCl3 to microalga S. quadricauda. Acidification of the aquatic environment increases the solubility, availability and toxicity of not only aluminum, but also other potentially toxic metals. Keywords: acidifi cation; рН; aluminum; toxicity; Scenedesmus quadricauda. DOI: 10.25791/esip.04.2019.567 Contacts: E-mail: miheev_m.93@mail.ru Pp. 03-11.