The Impact of Nigerian Flood Disaster on the Soil Quality of Farmlands in Oshimili South Local Government Area Of Delta State, Nigeria.

Abstract

Soil samples from flood disaster affected farmlands in Oshimili South Local Government Area of Delta State, Nigeria, were collected and analyzed for their physicochemical characteristics and heavy metal levels, in order to assess the impact of the flood disaster on the soil quality of the farmlands. The pH values in all the sites ranged from 5.20 to 6.10 with mean value of 5.45 indicating that the soils were moderately acidic. The electrical conductivity values which ranged from 52.80 to 89.40 with mean value of 69.70µScm^-1 imply significant presence of soluble inorganic substances with their respective ions. Total Organic Carbon and Total Nitrogen values ranged from (%) 0.38 to 1.76 and 0.021 to 0.143 with mean values of 1.08 and 0.09% respectively suggesting presence of some organic matters and compostable materials in the soils. Phosphorus content of the soil samples ranged from 17.21 to 37.20mgkg^-1 with mean value of 24.68mgkg^- which may be attributed to some submerged food crops like cassava tubers lost to the flood. Cation Exchange Capacity values ranged from 5.50 to 16.24 with mean value of 12.83Cmolkg^-1, which are suggestive of the soil capacity to adsorb metals. The mean heavy metal concentrations were (mgkg^-1) 33.57 for Fe, 5.03 for Zn, 5.99 for Cu, 12.78 for Mn, 3.91 for Co, 0.55for Ni, 0.40 for Cr and 0.43 for Pb. The levels were in the abundance trend of Fe > Mn > Cu, Zn > Co > Ni > Pb > Cr. The geoaccumulation index values of the metals in the soils revealed that the soils were practically uncontaminated by Ni, Cr, and Pb, slightly contaminated by Fe, Zn and Co and generally slightly contaminated by Cu. Contamination/Pollution index values indicate that all the metals studied were in the range which showed very slight contamination except Cu and Mn whose values were generally in the range of slight contamination. The over all results from the study indicated that the soils in all the sites were contaminated with heavy metals. However, the metal concentration levels found in this study do not pose any health hazard since the levels were below DPR target limits, and common range for agricultural soils.

Keywords: Nigerian flood disaster, soils, farmlands, heavy metals, physicochemical characteristics, pollution.