Determination of Some Heavy Metals Concentrations in Water and Irrigation Farms along Wulmi River in Pankshin Local Government, Plateau State, Nigeria

Levels of four heavy metals (Co, Cu, Pb and Cd) and three physico-chemical parameters (pH, temperature, total dissolved solids) were determined from Wulmi River at five sampling points (S1-S5) at an interval of 200m between points using atomic absorption spectrophotometer (AAS) and approved standard procedures respectively, and the control site located about 1000 meters away from the study area. Sampling was done monthly in wet season from May-December 2017. The weighted means of physico-chemical parameters determined at each sampling point in the river were in the range 6.53±0.21 - 6.85±0.17 for pH. 25.35±0.79 0C - 25.92±2.310C for temperature which is within the permissible limit of 300C (USEPA,2002), 9.43±3.90 mg/l - 26.71±2.75 mg/l for TDS which is also within the permissible limit of 1000 mg/l (USEPA,2002). The weighted mean of heavy metal concentrations in water at sampling points in the river ranged between 0.11±0.07 mg/l - 0.29 ± 0.19 mg/l for copper, 1.17±0.39 mg/l - 1.76± 0.31 mg/l for cadmium, 0.08 ± 0.05 mg/l - 0.91±0.03 mg/l for lead, 1.53± 0.39 mg/l - 6.48± 3.36 mg/l for cobalt. The soil samples from five irrigation farmlands (F1-F5) around the Wulmi River were also analysed for the heavy metals concentrations. The heavy metals concentrations in the soil ranged between 12.27 ± 3.46 μg/g - 28.05 ± 1.99 μg/g for copper, 5.49 ± 3.09 μg/g - 17.92 ± 2.18 μg/g for cadmium, 2.24 ± 0.02μg/g - 9.85 ± 1.43 μg/g for Lead, 13.48 ± 3.72 μg/g - 27.82 ± 2.65 μg/g for cobalt .Lead and cobalt concentrations in the soils are within the permissible limit set by USEPA (2002) and WHO [1] of 10μg/g and 50μg/g respectively. All the metals under investigation have geo-accumulation input in soils around Wulmi River, except in irrigation farms 2 and 4 which have geo-accumulation input of Pb to be 0.00. Analysis of variance indicates that there is significant difference in pH, concentrations of TDS, Cd, and Co from one sampling point to another throughout the periods of analyses. The data generated will be used to develop a computer based time series model, which can be used to predict the concentrations of the heavy metals in the near future at these sampling points in Wulmi River.