Sani UBA, Rumah Murtala MOHAMMED Funtua Mustapha ADO,Abubakar SALISU and, Suleiman ISYAKU.

Keywords: Risk assessment, Dam Water, Sediment, Heavy Metals, Shika Dam, Nigeria.

Abstract 

The purpose of this study was to assess levels of contamination and risk assessment of water and sediment in Shika Dam, Zaria Kaduna State. The levels of physicochemical parameters and some toxic heavy metals in the dam’s water and sediments were determined using standard analytical methods adopted from USEPA and WHO (1994, 2012). A questionnaire was developed, validated by experts and used for the collection of data for risk assessment test. The results and data collected from the water and sediment samples were subjected to statistical analysis at p≤ 0.05 level of significance. Student t-test (ANOVA) statistics was used to test the relationship between the physicochemical parameters and the toxic heavy metals in both water and sediments samples. The findings of the study indicated that, the mean concentrations of Pb, Cd, Cu, Co, Cr, and Ni in the water samples were: 0.140, 0.046, 0.010, BDL, 0.100 and 0.013 mg/L respectively. However, the mean concentrations recorded in the sediment samples were: 0.166, 0.005, 0.013, BDL, BDL, and 0.009 mg/L respectively. It also indicated that, concentrations of Cu and Co both in water and sediment samples were found to be lower than WHO/USEPA (2012), permissible limits. The levels of concentration of Cr were found to be higher in water but lower in sediments samples. However, the level of concentration of Ni was lower in water samples but, higher in the sediment samples while the concentrations of Pb and Cd in the water and sediment samples were found to be higher than the WHO/USEPA (2012), guidelines, indicating pollution of these portions of Shika dam water and sediments. The high level of Pb and Cd in water and sediment samples might be attributed to runoff of wastewater from agricultural activities within the study area. The findings from the results of this study revealed that, the concentrations of all the parameters studied were statistically significant (P ≤ 0.05) among the sampling points which clearly indicates common pollution source. Similarly, concentrations of physicochemical parameters in both the water and sediments samples revealed that pH, TSS, alkalinity, PO₄^3--P, NH₄⁺-N , NO₃^–-N, NO₂^–_–N, SO₄^2-S in water samples are lower than the recommended limits but higher in the sediment samples from the four sampling points used for this research. Results of the risk assessment test carried out in both the water and sediment samples revealed that, the analyzed toxic metals have the following risk assessment indices:  Pd ˃, Cd

˃, Cu ˃, Co ˃, Cr ˃, and Ni.