Analysis of metal mixture toxicity to Leptothrix sp. using fixed ratio ray experimental design


  • Flostina Chidinma Ndu Department of Microbiology, Federal University of Technology, Owerri, Imo State
  • Oluchi Rose Colette Nlemolisa Department of Microbiology, Federal University of Technology, Owerri, Imo State
  • Ugochi Nneka Kemka Department of Microbiology, Federal University of Technology, Owerri, Imo State
  • Ifechukwu Enyinnaya Adieze Department of Microbiology, Federal University of Technology, Owerri, Imo State
  • Vivian Kelechi Gaius-Mbalisi Department of Microbiology, Federal University of Technology, Owerri, Imo State



Heavy metals, dehydrogenase activities, toxicity concentration addition model, independent action model


There has been associate degree increasing ecological and world public health concern related to environmental contamination by metals in recent years. The current study is aimed toward analyzing metal mixture toxicity to Leptothrix sp. The various quantitative relation of toxicities of binary [Pb (II) + Ni (II), Cd (II) + Ni (II)] and ternary [Cd (II) + metal (II) + Ni (II)] mixtures of metals in addition because the toxicity impact of individual metal ions to Leptothrix sp. were assessed by using inhibition of dehydrogenase activity as associate degree finish purpose. Uniform design concentration relation (UDCR) and equieffect concentration relation (EECR) mixtures were designed to evaluate the combined toxicities of those significant metal ions. All the dose-response relation- ships of the UDCR and EECR mixtures and also the individual metal ions were delineating by logistical operates. The EC50 of the individual metal ion and their mixtures were calculable using logistical function. The Duncan test take a look at indicated considerably totally different EC50 values for every of the metal ions. Isobolographic and toxic index analyses showed doable interaction among the metal mixtures. The metal ions progressively inhi-bited  the dehydrogenase activity because the concentrations were increased, giving percent inhibitions bigger than 95 % at 0.2 mM Cd(II) and 0.4 mM Pb (II). The percentage inhibition of Ni (II) was greater than 85% at 0.06 mM. The binary and ternary mixture ratio shows inhibitory effect of the dehydrogenase enzyme activity as the concentration incresases. Generally, the binary mixtures Cd (II) + Ni (II) mixture were antagonistic, Pb (II) + Ni (II) were Synergistic expect for percentage mixture of Pb (II) 31.21% + Ni (II) 68.79% that is additive. The Cd (II) 20 % + Ni (II) 80 % and Pb (II) + Ni(II) EECR 50 were additive. The ternary mixtures were all antago- nistic. It is clear that heavy metals are the major sources of environmental pollution sometimes caused by anthro-pogenic activities; thus it is necessary for industries to treat these effluents before its discharge to the environ-ment.


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How to Cite

Ndu, F. C., Nlemolisa, O. R. C., Kemka, U. N., Adieze, I. E., & Gaius-Mbalisi, V. K. (2024). Analysis of metal mixture toxicity to Leptothrix sp. using fixed ratio ray experimental design. EQA - International Journal of Environmental Quality, 59, 1–12.