DEPARTMENT OF ENVIRONMENTAL MANAGEMENT AND TOXICOLOGY.

The discharge of wastewater into waterbodies without proper treatment has led to several threats such as DNA damage to aquatic species. This study evaluates the genotoxic effect of cassava wastewater on the gonads, liver and gills of post juvenile Clarias gariepinus using comet assay. The post juveniles of Clarias gariepinus was purchased from fish farm located in Delta State and was exposed to various concentrations (0.2%, 0.3%, 0.5%, 0.7%) of cassava wastewater for 96 hours. Unlike normal behaviours observed in the control groups, the fish exposed to the effluent were restless, erratic in their movement and gasping for breath. After the exposure period, the fishes were transported to the laboratory and the cells of their liver, gills and gonads were extracted for genotoxic assessment using comet assay. The result obtained from the genotoxic assessment revealed DNA damage at varying concentrations of the wastewater. The study revealed that genotoxins present in the wastewater were obviously responsible for the DNA damage in the tissues in the organism. The study also revealed that the genotoxic effect of cassava wastewater on post juveniles of Clarias gariepinus is dose
dependent as DNA damage increases with increased concentration. This study shows that the treatment of wastewater before disposal is very important.

This study investigated the effect of water soluble fractions of crude oil on the growth of Monoraphidium contortum and Dimorphococcus lunatus over a 14 day period. The test algae were grown in concentrations of CHU 10 nutrient media mixed with varying concentrations of WSF of crude oil (5%,10%, 25%, 50%, 75% 100%) which were prepared in triplicates. The growth response was measured using a visible spectrophotometer at two day intervals over a 14 day period. Physicochemical parameters (pH, EC, and TDS) were assessed on day 14 of the experiment and were compared to the stock concentration before exposure to the test microalgae. The results showed that there was growth stimulation for all concentrations of 0%, 5%,10%, 25%, 50%,75%, and 100% from day 0 to day 2, and a lag phase from day 2 to day 4 for 10% and 100%. The highest growth was recorded at 5% concentration on day 14
with an absorbance value of 0.035, followed closely by 100%, 50%, and 75% concentrations, while 10% WSF showed the least growth on day 14 with an absorbance value of 0.02. Statistically, the growth response of the microalgae to the WSF concentrations did not differ significantly (p > 0.005). Generally the percentage yield was higher in M.contortum compared to D.lunatus. The physicochemical properties of Dimorphococcus lunatus and onoraphidium contortum showed that when the quantity of WSF was reduced, both TDS and electrical conductivity rose. On the other hand, the pH revealed that it was somewhat more alkaline with a lower WSF concentration, suggesting acidity with a higher WSF. To summarize, Dimorphococcus lunatus exhibited a strong inhibitory reaction, and Monoraphidium contortum is better suited for bioremediation of crude oil in contaminated water.

Decrease in air quality has been a major concern in the world for decades and it has continued to worsen with dangerously toxic pollutant gases accumulating at a rapid rate every second. The atmosphere has majorly been polluted as a result of human day to day activities and these activities reduced a great deal during the covid-19 pandemic when a lockdown policy was established. The study area which is Lagos state, Nigeria is the state with the highest population count making it most prone to the spread of the covid virus and as such had the strictest policy regulation. This study was carried out to assess the effect of the covid-19 lockdown policy on air quality in Lagos state. The study adopted geographic information systems (GIS) using the Sentinel-5P data to obtain information on the concentration of Nitrogen dioxide (NO2), Particulate matter (PM2.5), Carbon monoxide (CO) and Sulphur dioxide (SO2) as parameters for air pollution for the year before the lockdown (2019), the year of the lockdown (2020) and the year after the lockdown (2021) which were compared and the results were analysed statistically to determine a significant difference in the concentrations per year. The data showed the year2020 had less concentrations of PM2.5 and NO2 which increased in 2021 when human and vehicular activities were back to normal, while SO2 and CO concentrations were higher in 2020
than in 2021 as a result of the increase in the use of indoor air pollution sources.