Assessment of selected heavy metals concentrations in Mairua Reservoir, Funtua, Katsina State, Nigeria for fishing purposes

Abstract

An assessment of selected heavy metal concentrations for fishing purposes was conducted at Mairua Reservoir, Funtua, Katsina State, Nigeria. This study aimed at assessing the selected heavy metal concentrations to enable the and sustainable use of the reservoir. Fishing is the major activity of the dwellers throughout the year, but there is less attention in considering the water quality in the reservoir. Eating fish harvested from polluted aquatic habitats could endanger the health Eating fish harvested from polluted aquatic habitats could endanger the health of the consumer. As such, there is the need of this research now if not continuously.
Water samples were taken in five sampling points and the procedural plan was the monthly sampling of the water from February-April and June-August 2020. The heavy metals include Zinc (Zn), Iron (Fe), Nickel (Ni), Manganese (Mn), Cadmium (Cd) and Lead (Pb). Laboratory procedures include sample digestions in preparation for spectrophotometric analysis using Atomic Absorption Spectrometer (AAS).  Data were analysed using Analysis of Variance (ANOVA) and independent t-test and related with FAO standard for fishing. The finding shows that most of the parameters like Cd, Zn and Pb are more in concentration at SPIII (downstream), i.e. the outlet of the water in the reservoir. It can also be seen that two parameters Fe and Ni are more concentrated at SPIV (middle towards east) and only Mn is higher at SPI (upstream). Furthermore, the analysis of variance revealed no significant difference (p >0.05) in the values of all the parameters across the five sampled collection points. The results of this study show that with the exception of cadmium (Cd) and lead (Pb), the heavy metal concentrations in water did not exceed FAO (2006) standards. However, Cd and Pb exceeded the FAO standard.  The level of heavy metal concentrations was compared based on seasons (wet and dry) using independent t-test at the 0.05 level of significance. The result shows no significant difference at 0.05 between the wet and dry season values of Fe (P value 0.106), Cd (P value 0.614) Zn (P value 0.700), Mn (P value 0.950), and Ni (P value 0.937). Study on Pb concentrations revealed that the metal was affected by seasonal variation (P value 0.047). Dumping waste very close to the reservoir should be discouraged. Farmers around the reservoir should be enlightened on the negative effects of their activities into the body of the water. More studies should be carried out on physico-chemical, microbial and other heavy metal concentrations in order to provide baseline information on the ecological status of the reservoir. In line with the finding, it is recommended that for effective fishing activities in the reservoir, the use of agrochemicals and dumping municipal waste very close to the reservoir, which could be the possible sources of Cd and Pb, should be discouraged.