ABSTRACT

Heavy metal concentrations posed a serious threat on agricultural soil in the Niger Delta area of Nigeria. Continuous oil exploration increased the heavy metal pollution level due to oil spill on agricultural land and agricultural produce from this polluted soil is of high health concerns. However, the impact of these pollutions on agricultural soil has not been adequately or scantly documented in Nigeria. Therefore, this study was carried out to quantify physico-chemical parameters and pollution load due to heavy metal contamination on spill sites among three locations in Rivers State. The study was conducted at three locations at close proximity to oil production sites of Eleme, Ahoada and Oyigbo areas of Rivers State that normally experience oil spillage on agricultural land. Five oil spilled sites were selected from each of the locations and non spilled sites to serve as control. A total of forty five samples were collected from spill sites and twenty seven from the control points at three depths of 0-15 cm, 15-30 cm and 35-45 cm. The physico-chemical parameters and heavy metal contents were determined using standard methods. Data were analyzed using descriptive statistics t-test and analysis of variance (ANOVA) at 5% probability level (p

<0.05).Across the locations, the mean concentrations of the physico-chemical parameters (pH, EC, NO3, TN, TP, SO4 and AP) recorded significant difference with depths. This was observed at the spill and control points (pH 6.16±0.38 and 6.56±0.61, EC 64.60±15.28 and 123±19.06 j.tS/cm, NO3 0.05±0.02 and 0.35±0.12 mg/kg, TN 0.23±0.16 and 0.53±0.08 mg/kg, TP 5.98±1.78 and 15.24±2.53 mg/kg, SO4 58.35±10.99 and 9.82±2.34 mg/kg and AP 1.97±1.10 and 8.00±1.69 mg/kg at depth 0-15cm respectively).At the spill locations at different depths, the concentrations of the heavy metals (Cu, Ni and Zn) varied insignificantly to each other (Eleme, Cu = 1.97±0.71 mg/kg, Ahoada 2.16±0.79 mg/kg and Oyibgo 1.22±0.53 mg/kg at depth 0-15 cm) except Cr (10.53±3.44 mg/kg, 22.52±8.13 mg/kg and 5.83±4.85 mg/kg) which was significantly higher than stipulated analytes of interest at same depth/location respectively. The pollution load cited that Oyigbo (0.89±1.53) and Ahoada were not polluted unlike Eleme (2.05±1.88), which was slightly polluted at depth 0-15 cm. At 15- 30 cm, Oyigbo and Ahaoda were also slightly polluted whereas Eleme (4.59±1.40) was strongly polluted .This is applicable to 30-45cm across the locations. The polluted soil should be Remediated to bring back the Agricultural soil to status quo to revitalize Agricultural productivity. >