Poor irrigation water quality due to oil spillage on surface water can result in food insecurity, health and economic challenges. This paper investigated the effect of total petroleum hydrocarbon (TPHC) and lead (Pb) on irrigation water quality in the oil spill prone area of the Niger Delta region of Nigeria. Water samples were taken from five different sections labelled A, B, C, D, and E along the Choba River, in Rivers State, Nigeria. Sections B, C, D and E were direct industrial effluent discharge points while section A was without direct industrial effluent discharge. Standard methods were employed in the water sampling and analysis. Suitability of Choba river water for irrigation was assessed by comprehensive pollution index (CPI) that incorporated salinity, sodicity, and permeability hazard potentials as well as the specific toxicity hazard potentials of TPHC and Pb. Results showed that all primary water parameters except pH were within the Food and Agriculture Organization (FAO) guidelines. The pH was low, ranging between 4.48 and 5.6. TPHC values for four out of the five samples were greater than the 10mg/l guideline as recommended by the Directorate of Petroleum Resources for surface water. TPHC for the four samples ranged between 14.52 and 174.32mg/l. The parameters with the most impact on CPI include EC, PI and TPHC with TPHC having the most impact. Water samples from sections A, B and E with CPI values 0.14, 0.37, and 0.8 respectively were classified in the clean, sub clean and slightly polluted categories respectively, while water samples from sections C and D with CPI values greater than 1 range from moderately to heavily polluted and not suitable for agricultural irrigation. Only water sample A was found suitable for irrigation.

The kinetics, equilibrium and thermodynamic study of the adsorption of Ni²⁺, Pb²⁺ and Cu²⁺ions from aqueous solution by the leaf of Mangiferaindica were investigated at different experimental conditions. Optimum conditions of initial metal ion concentration, pH, adsorbent dose, contact time and temperature were determined. The kinetics studies indicate that the adsorption process of the metals ions followed the pseudo second-order model with R² value of 0.9938, 1.00 and 1.00 respectively. Equilibrium studies showed that the adsorption of Ni²⁺, Pb²⁺ and Cu²⁺ ions are well represented by both Langmuir and Freundlich isotherm but the Langmuir model gave a better fit for Pb²⁺ ions with R² value of 0.9950 and Langmuir constant K_L of 4.3383 while Freundlich isotherm model best fit the experimental data of lead(II) and nickel(II) with a R² value of 0.976 and 0.9973 and Freundlich constant K_F value of 4.2677 and 0.0874. The calculated thermodynamics parameters of Ni²⁺, Pb²⁺ and Cu²⁺ ions are ( ΔG^o -1182.49,-5479.1 and 613.48 KJ/mol) showed that the adsorption of Ni²⁺ and Pb²⁺are spontaneous while Cu²⁺ non-spontaneous. The findings indicate that the leaf of Mangiferaindica could be used for the adsorption of Ni²⁺, Pb²⁺ and Cu²⁺ ions from industrial effluents.