Journal of Materials Science Research and Reviews

Background: Spent engine oil (SEO) affects soil physico-chemical parameters and plant productivity, but the interactive effects of nanozinc oxide (n-ZnO) in soils polluted with SEO and its impacts on the growth performance of plants in SEO polluted soil have not been fully explored. Upon entering the soil, the interaction of the SEO with the soil may alter its properties due to attachment or adsorption to soil components, which can affect the soil ecosystem. These pollutants accumulate in the soil, leading to long-term contamination with attendant effects on soil health and plant productivity.

Aim: The study aimed to assess the effects of n-ZnO on the physicochemical properties of soil polluted with spent engine oil and the growth performance of F. benjamina.

Materials and Methods: A 12-month Screen house experiment was conducted in the Institute of Ecology and Environmental Studies, Obafemi Awolowo University, Ile Ife, Nigeria using sandy loam soil treated with six levels of SEO (0, 0.5, 1.0, 1.5, 2.0, and 2.5 L/kg) with and without 50 ppm n-ZnO arranged in a completely randomized design. Pre- and post-harvest soil physicochemical parameters (pH, total nitrogen, organic carbon, phosphorus, exchangeable bases, cation exchange capacity, and moisture content) were analyzed using standard methods. Plant growth parameters such as height and number of leaves were monitored bi-weekly. Data were analysed using appropriate statistical methods. Data sets that met the assumptions of normality were analysed using one-way analysis of variance (ANOVA). Differences between treatment means were assessed using Duncan’s Multiple Range Test (DMRT) at a significance level of p ≤ 0.05.

Results: Results indicated that SEO contamination significantly reduced soil pH, phosphorus availability, exchangeable bases, and moisture content, but increased the total nitrogen and organic carbon due to hydrocarbon residues. High concentrations of SEO (≥2.0 L/kg) led to stunted growth and caused up to 100% plant mortality. At 0.5 L/kg SEO without amendment, F. benjamina showed a 20.8% reduction in height and a 23.9% reduction in leaf number compared to the control. However, the application of 50 ppm n-ZnO mitigated these adverse effects. Notably, F. benjamina grown in 0.5 L/kg SEO amended with n-ZnO increased the plant height by 16.1% and number of leaves by 6.7%, while at 1.0 and 1.5 L/kg SEO, n-ZnO amendment led to increases in height by 19.8% and 0.7%, and in leaf number by 21.8% and 37.8% respectively in relation to the plants in the SEO unamended soils. Although SEO contamination reduced soil pH slightly, differences across treatments were not statistically significant (p > 0.05). Control soil had a pH of 6.6, while SEO-treated soils ranged from 6.44 to 6.40. The observed ameliorative effects of n-ZnO were attributed to its high reactivity, increased nutrient bioavailability, and stimulation of soil microbial activity, which improved soil fertility and plant resilience.

Conclusion: This study concludes that n-ZnO is a promising amendment for remediating SEO-contaminated soils and enhancing plant growth. The findings underscore the potential of integrating nanotechnology into sustainable environmental management practices. Further studies are recommended to assess long-term ecological impacts and the potential bioaccumulation of nanoparticles in plants under field conditions.