1 Department of Industrial Microbiology and Brewing, Nnamdi Azikiwe University, Awka, Anambra State. Nigeria.
2 Department of Biological Sciences, University of Agriculture and Environmental Sciences, Umuagwo, Imo State, Nigeria.
3 Department of Microbiology, School of Biological Sciences, Federal University of Technology Owerri, Imo State, Nigeria.
Research Article
World Journal of Advanced Research and Reviews, 2023, 17(03), 206-223
Article DOI: 10.30574/wjarr.2023.17.3.0334
Received on 16 January 2023; revised on 27 Februay 2023; accepted on 02 March 2023
The influence of mixtures of metals and pesticide on the activity of algal hydrolytic enzyme alkaline phosphatase was investigated. Toxicity of unary and ternary combinations of Copper (Cu2+), Zinc (Zn2+), Lead (Pb2+), Chromium (Cr2+), Cadmium (Cd2+) ions and 2,4-dichlorophenoxyacetic acid (2,4-D) was assessed via inhibition of phosphatase enzyme activity of Chlorella vulgaris. The effects of the amalgamated ternary mixtures were studied in their fixed percentage ratio of 20:40:40 and 40:30:30. Results obtained showed that all the unary heavy metal ions were toxic to algal phosphatase activity, with a concentration dependent inhibition of alkaline phosphatase activity. The analysis of eco-toxicity concentration (EC50) of toxicant ternary mixtures of metals/ pesticides mixtures in 20:40:40 ratios show that the ternary mixtures 2,4-D/Pb2+/Cd2+and 2,4-D/Zn2+/Cd2+ were more toxic, followed by 2,4-D/Cu2+/Cr2+, 2,4-D/Pb2+/Zn2+, 2,4-D/Cu2+/Zn2+ and 2,4-D/Cu2+/Cd2+. Whereas among the 40:30:30 mixture ratios 2,4-D/Pb2+/Cd2+ and 2,4-D/Zn2+/Cd2+ were most toxic. The decline in the trend of their toxicity strength was followed by 2,4-D/Cu2+/Cr2+, 2,4-D/Cu2+/Zn2+, 2,4-D/Cu2+/Cd2+, 2,4-D/Cu2+/Pb2+ and 2,4-D/Pb2+/Zn2+. In addition, the least toxic amongst them were the 2,4-D/Pb2+/Cr2+, 2,4-D/Zn2+/Cr2+ and 2,4-D/Cr2+/Cd2+ ternary mixtures. Toxicity index analysis of the mixture interaction effect showed that the mixtures of heavy metals with 2,4, D were mostly antagonistic with toxic index (TI) >>1, However, exceptions were the 2,4-D/Pb2+/Cd2+ and 2,4-D/Pb2+/Cd2+mixture which were additive and synergistic with TI=1 and TI<1 respectively. From the foregoing study, the toxicity of the mixtures exhibited largely sigmoidal relationship, increased composition of heavy metal in the mixture resulted in a potentiation of 2,4-D toxicity. These results indicate that mixtures of heavy metals with largely non-toxic 2,4-D may pose ecological risk to freshwater microalgae Chlorella vulgaris, presenting antagonistic, additive and synergistic toxicity interactions based on their relative occurrence in the mixture.
Toxicity; Mixture; Alkaline phosphatase; 2,4-dichlorophenoxycetic acid; Heavy metals; Chlorella vulgaris
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Romanus Ugochukwu Onyeukwu, Emeka Sabastine Asiwe, Christian Okechukwu Nweke and Vivian Kelechi Gaius-Mbalisi. Toxicity of single and ternary mixtures of heavy metals and 2,4-dichlorophenoxyacetic acid to Chlorella vulgaris alkaline phosphatase activity. World Journal of Advanced Research and Reviews, 2023, 17(3), 206-223. Article DOI: https://doi.org/10.30574/wjarr.2023.17.3.0334