Physico-chemical and Heavy Metal Assessment of Soil and Water in the Vicinity of Petrol Stations in Karu Local Government Area, Nasarawa State, Nigeria

Soil and water exposure to petroleum at petrol filling stations is believed to induce physicochemical changes and heavy metal pollution thus, this study investigated the extent. Using standard procedures; soil samples were collected 20-30 m apart and at a depth of about 0 – 20 cm while, water samples were collected within 30 m of the stations. At 500 m away from the stations, samples were collected as control. Soil samples were analyzed for; pH (6.25±0.25 to 6.78±0.28), Temperature (29.0±0.49 to 30.5±0.71 °C), Total Dissolved Solids (358 ±1.00 to 620±1.00 mg/kg), Electrical conductivity (719±1.00 to 1248±1.20 μS/cm), Cation exchange capacity (6.80±0.30 to 11.2±0.30 mol/kg), Moisture content (3.50±0.30 to 7.00±0.30 %), Organic carbon (0.20±0.20 to 1.68±0.28 %) and heavy metal content (mg/kg): Cr (12.5±0.02 to 72.6±0.63), Cu (5.47±0.36 to 51.8±1.55), Fe (1525±25.10 to 2023±5.29), Ni (1.97±0.01 to 30.2±0.18), Mg (118±0.67 to 184±4.65), Mn (86.2±0.20 to 394±0.54), Pb (3.08±0.08 to 12.2±0.12) and Zn (12.4±0.46 to 157±0.70). Water samples were also analyzed for; pH (7.50±0.50 to 7.71±0.30), Temperature (30.0±1.00 to 30.7±0.70 °C), Total Dissolved Solids (33.0±1.00 to 48.0±1.00 mg/L), Electrical conductivity (66.0±1.00 to 98.0±1.00 μS/cm), Dissolved Oxygen (2.60±0.30 to 4.80±0.30 mg/L), Biological Oxygen Demand (6.25±0.25 to 14.2±0.20 mg/L), Turbidity (ND to 1.90±0.30 NTU) and Hardness (84.0±1.00 to 380±1.00 mg/L) and heavy metal content (mg/kg): Cr (0.187±0.004 to 0.257±0.002), Cu (0.101±0.012 to 0.112±0.008), Fe (ND to 0.019±0.007), Ni (ND to 0.020±0.002), Mg (6.06±0.203 to 6.63±0.105), Mn (0.057±0.002 to 0.360±0.004), Pb (0.042±0.000 to 0.072±0.001) and Zn (ND to 0.037±0.002). Even though, wide variability was observed in some instances, no significant impacts on soil and water were recorded as affirmed by their respective controls. In addition, determined parameters were on average within the acceptable threshold limits set by standard regulatory bodies like NESREA, DPR, NSDWQ and WHO except for EC, Fe and Mg in soil and Cr and Pb in water, in all samples.