Hydrocarbons in crude-oil production sites of the Sudd-region South-Sudan: Implication on soil fertility and plant species risk

Crude oil activities lead to soil contamination with hydrocarbons, this drastically affects normal functioning of the soil and result in nutritional constraints; thus, negatively affect plant growth, and low productivity. These studies were objectively incepted to determine the effects of crude oil on soil properties and spatial distribution of plant species in oil production sites in South-Sudan. Soil samples were taken at two depths of 0-30cm and 30-60cm within 1m2 quadrats located at different distances of 0-1km (drilled-land); 5km (Cultivated land) and 50km (natural-land). The soil samples were analyzed for Total petroleum hydrocarbons (TPHs) and physicochemical properties; also herbaceous plant species were counted and identified within the same quadrats. Results showed that surface and subsurface soils in the drilled lands were highly contaminated with TPHs. Locations 5Km away from the drilled wells were also contaminated with hydrocarbons when compared to the critical limits of Sudan of 5000mg kg-1 soil and the Canada-Wide Standard of 5600mg kg-1 soil for petroleum hydrocarbons. Similarly, all the soil chemical properties analyzed deteriorated with increasing TPHs concentration. Therefore, land use change from natural to oil exploration without proper management leads to reduction in soil fertility, rendering the soil unsuitable for agricultural productivity purposes. Concentrations of hydrocarbon contaminants call for urgent need for remedial treatments as a strategy to rejuvenate soils of the Sudd region. In drilled lands the dominant plant species were, Sorghum arundinaceum, Oryza longistaminata, Hyparrhenia rufa, Nicotiana tabacum, Gossypium barbadense and Abelmoschus ficulneus. The abundance of such plant species in the crude oil drilled lands support the assertion that, they are tolerant to hydrocarbons. However, these plant species need testing for their ability and efficiency to accelerate hydrocarbon degradation, thereafter be used as phyto-remediators to eliminate the threat to soil fertility and plant diversity in the world's biggest wetlands, the Sudd in South-Sudan.