Influence of soil acidity on the results of bioassay

• A.M. Sheromov

  Vyatka State University, 36, Moskovskaya, 610000, Kirov, Russian Federation

  Автор

• A S. Olkova

  Vyatka State University, 36, Moskovskaya, 610000, Kirov, Russian Federation

  Автор

The physicochemical properties of soil, including acidity,
determine the scientific validity of interpreting bioassay results. The toxicity of
heavy metals (HM), as common soil pollutants, may vary depending on soil properties. This study aimed to develop a rapid bioassay method that is tolerant of
low pH values and sensitive to heavy metal pollution in soil under simulated
laboratory conditions. Podzol from a spruce forest in Kirov Oblast, Russia, was
cultured for 30 days in two main experimental groups: one group was treated with
copper and zinc salts under naturally high acidity (pH = 4.62), while the other
group was treated under similar pollution conditions with pH neutralization using
dolomite powder. Bioassays of the water extract (1:4) were performed using the
ciliate Paramecium caudatum Ehrenberg and Escherichia coli Migula («Ecolum»).
The bioassay results showed that Escherichia coli was more sensitive to heavy
metal toxicity than Pseudomonas caudatum. High toxicity index was recorded in E.
coli tests: 330 mg/kg for copper and 110 mg/kg for zinc in strongly acidic soils, and
2750 mg/kg for zinc in weakly acidic soils after dolomite was added. Based on
these results, it is recommended to use E. coli-based bioassays for environmental
control and acid soil monitoring, as E. coli exhibits high tolerance to acidic
environments.

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