Abstract
PurposeThis study sought to investigate the effects of organic amendments on the degradation of hydrocarbons and vegetative properties of Zea mays grown in crude oil-contaminated wetland soils of the Niger Delta, Nigeria.MethodsTwo soil types were investigated, namely, fadama soil (oxisol) and swamp forest soil (utisol). For each soil type, 48 treatment cells and 1 control containing 1 kg of soil each were spiked with crude oil at concentrations ranging from 50 to 200 g kg−1, representing 5–20% (m/m) contamination levels, respectively. Then, 5 days after the contamination, the soils were amended with cow dung (CD), poultry waste (PW), and palm oil waste (POW). The ratios of soil to organic amendments used were 1:1 and 2:1. The soils were tilled and irrigated regularly, and monitored for a total period of 112 days. The same conditions were used to investigate the vegetative properties of Z. mays in these oil-contaminated soils with organic amendments.ResultsThe total organic carbon (TOC) and pH increased significantly within the first 2 weeks after crude oil contamination; thereafter, the pH of the soil decreased significantly over incubation time, while there was steady increase in TOC with incubation time. The percentage nitrogen and total petroleum hydrocarbons (TPH) decreased significantly. The utisol soil showed better plant performance, despite the lower hydrocarbon degradation rate.ConclusionThe organic amendments showed a TPH degradation trend that followed the order: PW > CD > POW. They also improved the seed emergence of Zea mays.
Highlights
Soil contamination by petroleum hydrocarbons is a widespread global environmental issue because of the heavy reliance on petroleum as a foremost source of energy
The objectives of this study were to determine (1) the effects of organic amendments, namely, cow dung, and poultry and palm oil wastes, on the degradation of petroleum hydrocarbons in selected soil types of the Niger Delta contaminated with crude oil, and (2) the effects of the organic amendments on the vegetative properties of Zea mays grown in crude oil-contaminated soil
The three different types of organic amendments, namely, cow dung was collected from the abattoir at Agbor, and poultry waste and palm oil waste were collected from a poultry farm and a palm oil processing mill in Obiaruku
Summary
Soil contamination by petroleum hydrocarbons is a widespread global environmental issue because of the heavy reliance on petroleum as a foremost source of energy. The discharge of hydrocarbons into the environment by accident. The Niger Delta of Nigeria is a densely populated petroleum-rich area. This fragile ecosystem has been severely impacted by the effects of oil. The degradation of Niger Delta soils is related to oil spills in the region, of which there have been many thousands of incidents. The soil flora and fauna in this area are under serious threat because of the deleterious effects of crude oil. Oil spills occur mainly as a result of equipment failure, corrosion and vandalization
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