Status of Soil Quality in the Vicinity of Artisanal Refining Sites in Rivers State, Nigeria

Abstract

The environmental quality and sustainability in the Niger Delta region are severely undermined by the increasing practice of artisanal crude oil refining. This study aimed to assess the impact artisanal crude oil refining on soil nutrients stability vis-à-vis plant/vegetal resources of farmlands. Farmlands in Elele-Alimini and Ibaa in Emohua Local Government Area (LGA), Ogbodo in Ikwerre LGA and Umuanyagu (control) in Etche LGA, Rivers State (Nigeria) were sampled in this study. A total of fifty (50) sampling points in both test and control locations, were randomly selected using a standard spatial (grid-based) sampling technique. Soil and plant samples within the farmlands were collected to determine the physicochemical parameters and macronutrient contents. During the dry and wet seasons, mean values of pH, EC and moisture content in test soil were in the ranges 4.60-4.85 and 4.55-4.79; 66.67-130.0 µS/cm and 31.3-33 µS/cm, and 7.21-11.49 % and 11.71-66 %, respectively. The values of pH, EC and moisture content in the control soil ranged from 4.78-4.84 and 4.81-5.14; 130-152 µS/cm and 31.5-33.0 µS/cm, 11.86-11.88% and 63-66% respectively. Electrical conductivity and pH of soil showed almost a similar trend (Control > Ogbodo > Ibaa > Elele Alimini) for both top and sub-soils and in both seasons. During the dry and wet seasons, mean values of nitrogen (N), phosphorus (P), potassium (K), Total Organic Carbon (TOC) and Soil Organic Matter (SOM) in test soils were in the ranges 0.11-0.17% and 0.11-0.18 %; 0.13-0.23 mg/kg and 0.04-0.06 mg/kg; 22.82-51.87 mg/kg and 14.23-35.60 mg/kg; 1.30-2.00% and 1.36-2.0%, and 2.22-3.45% and 2.24-3.16, respectively. Mean values of N, P, K, TOC and SOM in control soils during the dry and wet seasons were in the ranges 0.12-0.19% and 0.14%; 0.29-0.33 mg/kg and 0.08-0.09 mg/kg; 50.33-52.18 mg/kg and 42.75-50.24 mg/kg; 1.35-2.14 and 1.83-2.08%, and 2.53-3.70% and 2.12-2.85%, respectively. The levels of N, P, K, TOC and SOM in the farmlands were low, and could result in poor crop growth yield.