IKPOBA RIVER

Heavy metals are ubiquitous contaminants in the aquatic ecosystems, posing significant threats to fishes and other aquatic fauna which tend to bioaccumulate this toxicant in their muscle. This study was therefore carried out to investigate the bioconcentration of heavy metals in the muscles tissues of fish fauna within Ikpoba River, Benin city. A total number of 26 (13 Clarias garipienus and Tilapia zilli) fishes were collected from Ikpoba River between June to August 2023. Heavy metals (Cd, Ni, Pb, Cr and Co) in the muscles of the fish were estimated using atomic absorption spectrometer (AAS), while the ratio of heavy metals in the muscles of the fish
relative to water, was estimated using the bioconcentration index. The result showed that Nickel in the muscles of the benthic fish had the highest concentration in the month of June (21.21mg/kg) and lowest in the month of July (14.92mg/kg), while Nickel in the pelagic fish had the highest concentration in August (21.82mg/kg) and lowest in July (12.89mg/kg). Lead and Cadmium were found to be below detectible limit in benthic and pelagic fish muscle tissue across the sampling period. Chromium in the muscle tissue of the benthic fish has the highest in June (10.89mg/kg) and lowest in July (4.85mg/kg), while in pelagic fish, it was found to be highest in August (12.91mg/kg) and lowest in June (6.11mg/kg). The concentration of cobalt in benthic and pelagic fish was found to be highest in the month of August (3.44mg/kg and 12.91mg/kg) and lowest in the month of June (1.93mg/kg and 6.11mg/kg) respectively. These variations therefore signify the level of heavy metal accumulation in their tissues which have impacts on the aquatic ecosystem and human health.

Ikpoba River is the major recipient for municipal waste and industrial effluent in Benin City,samples of water were collected at five different locations in the river for some selected heavy metal analysis in order to determine the extent of pollution. Samples were collected in August to December 2021. Chemical analyses of samples river water and Dam was collected at predetermined sampling points were undertaken, the observations obtained were subjected to ANOVAand correlation analysis. Results obtained showed that each point source has its relative contribution to the overall degradation of the river water quality. The heavy metals were determined with atomic absorption spectrophotometry (AAS). From river water and dam the heavy metal concentrationwere found to be in the increasing order, fe>zn>cu> pb>Cd for all the five samples point collection as show in the result analysis. It also shows that the lead was not present in one of the point and Cadmium were not also detection in all of five sample. The analyses carried out also show the level of phosphate, nitrate, magnesium, pH, BOD,DO, electrical conductivity and turbidity in all the five stations and the turbidity was also notice to be relatively high. Most of the heavy metal determine were below the maximum permissible limit set by FEPA and WHO

One of the most recent and emerging contaminants today, is plastic. These plastics through improper waste disposal and runoff, find their way to water bodies. This plastic when they fragment or occur in very small sizes (<5mm) are termed microplastic. They can be classified on physical characteristics or chemical characteristics. They pose risk to both fish and consumers of the fish. The fish samples were analysed within 24hrs of collection. The fish were digested using 10% KOH, and purified using H2O2. The filtrates were examined under microscope to identify the microplastic particles, which were physically confirmed using the hot needle method and confirmed chemically using Fourier transfer infrared spectroscopy. Microplastics occur at all stations through the three months under study. The microplastics found based on morphological characteristics are pellet, foams, fibre, filaments, and fragments, while on polymer characteristics, there were two namely; polypropylene and polyethene. The type of microplastic prevalent in each station had a relationship to the prevalent economic activities at the watershed. For example, at station 3 (Ikpoba bridge), the
prevalent economic activities at the water fronts are car and rug washes, the prevalent plastic is polypropylene