O. Ogbeide

Background: N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone (6PPD-quinone or 6PPD-Q), a pervasive transformation product of tire-wear antioxidants, has been identified as a highly toxic contaminant in urban stormwater runoff, responsible for acute mortality in sensitive salmonid fish. However, its sublethal, chronic, and mechanistic toxicity on non-salmonid freshwater species, such as the African Catfish (Clarias gariepinus), remains less understood. Objective: This study investigates the toxic effects of 6PPD-Q on the antioxidant defense system—specifically glutathione (GSH), glutathione peroxidase (GPx), and superoxide dismutase (SOD)—in Clarias gariepinus under sub-chronic exposure. Methodology: Clarias gariepinus fingerlings were exposed to environmentally relevant and higher concentrations of 6PPD-Q [0, 0.5, 1.0, 5.0 g/L] for a period of 28 days under controlled conditions. Liver tissues were analyzed for GSH levels, GPx activity, and SOD activity at 7, 14, and 28 days of exposure.
Results: 6PPD-Q exposure induced significant dose- and time-dependent oxidative stress in C. gariepinus. Initial exposure (days 7–14) resulted in a compensatory increase in SOD and GPx activities and GSH levels. However, prolonged exposure (day 28) to higher concentrations (1.0–5.0 g/L) led to a significant decrease in GSH levels and inhibited GPx and SOD activities, indicating an overwhelming of the antioxidant defense system. Conclusion: The results demonstrate that 6PPD-Q is highly toxic to Clarias gariepinus, inducing severe oxidative stress that disrupts key detoxification pathways. The inhibition of GSH, GPx, and SOD suggest that 6PPD-Q can trigger severe hepatic cellular damage and long-term health risks in this species, necessitating tighter monitoring of tire-derived pollutants in freshwater ecosystems.

Heavy metal contamination from mechanic workshops poses a major environmental challenge due to the continuous accumulation of toxic metals in soil, which can affect microbial activities, reduce soil fertility, and pose health risks to humans and other organisms. This study assessed the effectiveness of hydroxyapatite (HAp) and phosphate solubilising bacteria (PSB) (Pseudomonas sp.) in remediating heavy metal contaminated soil collected from a mechanic workshop. The research involved four treatments: soil only (control), soil + PSB, soil + HAp, and soil + PSB + HAp. Microbial counts and heavy metal concentrations (Fe, Cu, and As) were analyzed after incubation. The total heterotrophic bacterial count (THBC) increased from 2.5 × 10⁵ CFU/g in soil treated with PSB alone to 2.75 ± 0.71 × 10⁵ CFU/g in soil treated with both PSB and HAp, indicating enhanced microbial growth due to the combined amendment. The concentrations of iron (Fe) and copper (Cu) decreased significantly in all treated samples compared to the control. Fe reduced from 7561.97 mg/kg in the control to 6197.18 mg/kg in the combined treatment, while Cu decreased from 205.32 mg/kg to 150.19 mg/kg. Percentage reductions of 18.05% (Fe) and 26.85% (Cu) were recorded for the combined treatment, while arsenic (As) was not detected in any sample. These findings demonstrate that hydroxyapatite and Pseudomonas sp. act synergistically to immobilize and reduce heavy metal concentrations in contaminated soils. The combination improves microbial activity, enhances metal precipitation, and reduces the bioavailability of toxic metals. The study concludes that the combined use of hydroxyapatite and phosphate solubilising bacteria is an efficient, low-cost, and environmentally friendly method for remediating heavy metal–polluted soils from mechanic workshops in Nigeria.

The complex mixture of pollutants found in industrial effluents can have a significant impact on soil organisms, especially earthworms, which are important for soil health. This study investigates the effects of exposure to industrial effluent on the growth and biochemical stress responses of Eisenia fetida , a well-known bioindicator species. Over the course of 28 days, earthworms were introduced weekly into varying concentrations of the effluent, along with a control group that was not exposed. To measure the effects of the effluent, we tracked important growth parameters, such as weight gain, body length, and reproductive output (cocoon production), at weekly intervals. We also examined biochemical markers of stress, such as superoxide dismutase (SOD), catalase (CAT), and total protein content, to assess oxidative stress and metabolic changes. The data were statistically analyzed to identify patterns of growth inhibitions, physiological adaptation, and Biochemical alterations over time. Our research showed that Eisenia fetida was clearly affected by the effluent in a dose-dependent manner. Significant decreases in weight, body length, and cocoon production were observed in earthworms exposed to higher concentrations, suggesting physiological stress and compromised reproductive ability. Biochemical analyses further confirmed these effects, with increased SOD and CAT activities suggesting an oxidative stress response. Meanwhile, the decline in total protein content pointed to metabolic distress and possible protein degradation, especially at higher effluent concentrations. To visually represent these trends, we used line graphs and bar charts to track changes in growth and biochemical markers over time. Additionally, picture documentation documented noteworthy morphological variations between exposed and control groups. These results underscore the substantial environmental concerns caused by industrial wastewater discharge and reinforce the need for tougher waste management policies. The significance of Eisenia fetida as a bioindicator for evaluating soil contamination and ecosystem health is highlighted by this study, which illuminates the harmful impacts of industrial pollution on soil organisms.

Welding is the process to join two or more similar or dissimilar metal with the applicationofheat and sometime pressure. Gas Tungsten Arc Welding (GTAW) is commonly knownasTungsten Inert Gas Welding (TIG Welding). Corrosion of metal is an ubiquitous phenomenonthat occurs in various forms. Atmospheric or uniform, galvanic, crevice, pitting, and microbial corrosion are most familiar forms of corrosion. The service life of engineering structuresisaffected by the quality and strength of the welded joints. The effects of corrosion affects thequality of the welded joints and the general structure. The offshore structures are exposedtothevarious environments, and it is well known that the corrosion rate and the corrosion mechanismunder each environment, marine atmosphere, splash zone, tidal zone, underwater zoneandbottom zone, are different. The aim of this study is to model the environmental effectsofcorrosion on tungsten inert gas weld joints of a mild steel pipe using response surfacemethodology. Mild steel pipe was cut into dimension 40mm in length, 12mm diameter and 3mmthickwithapower hacksaw, grinded and cleaned before the welding process. The experimental matrixwasmade of twenty (20) runs, generated by the design expert software adopting the central composite design. The response was measured, which is the rate of corrosion and then modelledusing the response surface methodology. The result obtained in this study shows that the current has a very strong influence on the rateofcorrosion. Based on the findings, it is summarized that the corrosion rate is minimumwhenawelding voltage of V = 18V, current = 120A and gas flow rate = 13lit/min. The response surfacemethodology employs certain statistical tools which are Anova, goodness of fit, coefficient ofdetermination and noise to signal ratio which determines the adequacy and significance of themodel developed. The result from this study shows that the model has a very good varianceinflation factor and p-value < 0.05. The model posseses favourable coefficient of correlation(R)value for the rate of corrosion