Insights into the effects of crude oil contamination on health status of soil and oxidative stress in plant using maize plant (Zea mays L.) as bioindicator.

Crude oil contamination alters soil health and induces phytotoxicity, with effects varying by soil properties and plant species. Understanding these impacts is crucial for developing effective bioremediation techniques for ecosystem restoration and plant conservation. This study evaluated effects of crude oil contamination (0-2.5% per kg soil) on soil health using biochemical, physicochemical, and biological parameters over a 12-week experimental period, with maize (Zea mays L.) as the test plant. Effects of crude oil contamination on enzyme distribution, physical and chemical properties of soil were monitored while oxidative stress in maize plants was determined at the end of the experimental period. Results showed that the activity of enzymes in control and test soils decrease with plant growth. Significant increase in activity was recorded in oil contaminated soils for dehydrogenase, α-amylase, β-glucosidase, cellulase, polyphenol oxidase, lipase, acid phosphatase and arylsulfatase when compared with control. Amidase and protease activities were significantly lower in contaminated soil compared to pure soil. Crude oil contamination increased bulk density and reduced pore size with minimal significant impact at 0.5% crude oil per Kg of soil. Bacterial population significantly increased in contaminated soils compared to pure soils. Oxidative stress in maize plant grown on 0.5% crude oil contaminated soil was not significant compared with control. Crude oil contamination induced oxidative stress at higher concentrations as revealed by increase in superoxide dismutase, catalase and guaiacol oxidase. Findings provide information that would guide the design of bioremediation techniques for restoration of crude oil contaminated soils.

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