Remediation of Hydrocarbon Polluted Soil Offsets Methanogenic Microbial Communities and Improves Soil Recovery of Crude Oil-Polluted Site

Abstract

Hydrocarbon pollution amplified by artisanal refining has led to the devastating destruction of farmlands and fishing settlements of subsistence farmers in the Niger Delta. The relatively slow natural attenuation of these polluted sites is the motivation for this study. The natural response and the influence of intermittent tillage and nutrient addition on bacterial community ecological functions were investigated using 16S rRNA metabarcoding. Representative soil samples were drawn from the surface (0 – 15cm) and subsurface (1m and 1.5m depths) of the polluted site pre-remediation and during remediation on Days 0, 14, 49, 70 and 91. Nutrient in the form of poultry droppings was added to the polluted soil while aeration was improved by tillage at 3-weeks interval throughout the duration of remediation. Total petroleum hydrocarbon was reduced from 93,720 mg kg–1 on timepoint zero to 9,029.76 mg kg–1 on day 91. Alpha diversity analysis revealed that the proportionality (evenness) of bacterial species significantly reduced during remediation. The bacterial community structure during remediation was significantly different compared to the structure pre-remediation. Spearman’s rank correlation revealed that soil pH, total phosphorus and total potassium were the chemical factors that influenced diversity. During remediation, the most responsive bacterial phyla were Proteobacteria and Cyanobacteria while Hydrogenedentes and Spirochaetes were among biomarkers pre-remediation. PICRUSt2-based functional prediction revealed that pre-remediation, pathways for methanogenesis and terpenoids biosynthesis were differentially abundant while high energy-yielding TCA cycle and pathways for both fatty acid biosynthesis and the degradation of aromatic hydrocarbons were differentially abundant during remediation. Overall, the addition of poultry droppings and intermittent tillage improved nutrient availability and this subsequently led to a significant change in the bacterial community structure and the rate of hydrocarbon sequestration. The authors concluded that incorporation of poultry droppings by tillage may serve as a suitable remediation method to reduce hydrocarbon in oil-polluted Niger Delta soils.

Field scale biodegradation of total petroleum hydrocarbons and soil restoration by Ecopiles: microbiological analysis of the process

“…Bacteria are known to degrade certain petroleum hydrocarbons. For example, Acinetobacter and Alcanivorax can degrade short and long-chain alkanes (Rojo, 2009;Wang and Shao, 2014;Obieze et al, 2021). Sphingomonas, Nocardia, or Rhodococcus are known to bioremediate anthracene.…”