The analysis of natural abundance isotopes in biogenic N 2O molecules can give precious information such as the nature of their precursor. However, many uncertainties exist and further validations are necessary to confirm this method as a reliable tracer of biogeochemical cycles. In particular, current methodologies (such as the isotopocule map approach) can only estimate the combined contributions of several processes at once. In this study, we aimed to develop a new methodology capable of individually discriminating the main sources of N 2O production in soil by combining natural abundance isotopes with the use of a 15N tracer ( 15N Gas Flux method). To achieve this, we conducted parallel laboratory incubations of an agricultural soil, during which we optimized the denitrification conditions through increase of moisture and amendment of nitrate; where this nitrate was either labelled or unlabeled with 15N atoms. A new linear system combined with Monte Carlo simulation enabled the determination of N 2O source partitioning, where bacterial denitrification was identified as the dominant process (87.6%), compared to fungal denitrification (9.4%), nitrification (1.5%) and nitrifier denitrification (1.6%). This new system has been compared to a recently developed stable isotope modelling tool applying Bayesian statistics (FRAME). The results agreed generally well at the exception of lower bacterial denitrification (80%) and higher nitrifier-denitrification (9%) contributions found with the FRAME model. This new approach provides a perspective for a wider application, potentially enabling the source partitioning of nitrous oxide emissions in agroecosystems.

Environmental pollution is generally caused by two main factors that include high rate of industrialization and rapid increase in population thereby putting more pressure on natural resources such as petroleum. As a result the petroleum industry affects the environment through oil spills causing many negative effects on human health and the surrounding ecosystem due to presence of toxic compounds in crude oil such as the Polycyclic Aromatic Hydrocarbons (PAHs) that is potentially carcinogenic to humans. The aim of this research is to investigate the efficiency of Chrypsopogon zizanioides also known as vetiver grass with the aid of bio surfactants and N.P.K. fertilizer in dissipating and containing organic pollutants in the soil. It is specifically focused on the 16 Polycyclic Aromatic Hydrocarbons (PAHs) classified by United States Environmental Protection Agency (US EPA) as priority pollutants. The general methodology involved a glasshouse experiment by growing the plant C. zizanioides in a freshly spiked oil contaminated soil and a weathered hydrocarbon contaminated soil from where the soil samples were treated with ramphnolipids including (95% (Mono-Rhamnolipid dominant) and 95% (Di-Rhamnolipid dominant) produced by Pseudomonas aeruginosa and N.P.K. fertilizer to promote plant and the microbial biomass. Some of the control samples were left uncontaminated (oil free) while others were left unplanted (plant free) to investigate the growth of the plant in the absence of oil and the fate (degradation) of crude oil in the absence of the grass. Thereafter, soil samples were collected periodically on monthly basis and the concentration of PAHs was assessed in the laboratory via Gas Chromatography Mass Spectrometry (GC MS). The result of this research has already indicated an improvement in plant and microbial biomass in all the samples treated with N.P.K. fertilizer and rhamnolipids after a period of 72 days. More plant culms and heights were observed to have emerged in samples treated with N.P.K. fertilizer only followed by samples treated with N.P.K. and biosurfactants. Furthermore, there has been a reduction in the concentration of the PAHs in the crude oil contaminated soils as a result of the combined action of C. zizanioides, ramphnolipids and N.P.K. fertilizer as compared to the control samples. It also highly anticipated that C. zizanioides may help in breaking down the PAHs in the weathered hydrocarbon contaminated soil.

Soil contamination is mainly attributed to certain factors such as industrialization and increasing population with negative impact on natural resources such as petroleum. The petroleum industry affects the environment through oil spills with negative effect on human health and the surrounding ecosystem due to presence of Polycyclic Aromatic Hydrocarbons (PAHs) that can be carcinogenic to humans. The aim of this research is to compare the effectiveness of Chrypsopogon zizanioides also known as vetiver grass under the influence of biosurfactants and N.P.K. fertilizer in degrading and immobilizing persistent oil pollutants particularly the 16 Polycyclic Aromatic Hydrocarbons (PAHs) classified by United States Environmental Protection Agency (US EPA) as priority pollutants. The experiment was conducted in a glasshouse by growing the plant C. zizanioides in a freshly spiked crude oil contaminated soil and a weathered soil added with biosurfactant (ramphnolipids) produced by Pseudomonas aeruginosa. Similarly, all contaminated samples were amended with N.P.K fertilizer to promote the growth of C. zizanioides and microbial activities. Likewise, the assessment of the (bio) distribution of the petroleum hydrocarbons particularly the PAHs was carried out via Gas Chromatography Mass Spectrometry (GC MS). The result of this research has already indicated an improvement in plant growth and biomass in samples amended with N.P.K. fertilizer. It is also highly anticipated that the findings of this research will help in dissipating persistent contaminants such as PAHs in the crude oil contaminated soils under the influence of C. zizanioides and ramphnolipids and N.P.K. fertilizer as compared to the control samples.