Research Article

Spatial Deposition of Soot and Polycyclic Aromatic Hydrocarbons around a Gas-Flaring Corridor in Omoku, Rivers State, Nigeria

Abstract

Gas flaring contributes to atmospheric particulate emissions and the deposition of polycyclic aromatic hydrocarbons (PAHs) in petroleum-producing environments. This study investigated the spatial distribution of soot deposition and PAHs around a gas-flaring corridor in Omoku, Rivers State, Niger Delta, Nigeria. Sampling was conducted at five distances (100, 250, 500, 750 and 1,000 m) from the flare corridor and at a reference location. Soot deposition, the 16 priority PAHs (Σ16PAHs), PAH deposition flux, benzo[a]pyrene toxic equivalency (BaP-TEQ), PAH ring-number composition and diagnostic ratios were evaluated. One-way analysis of variance (ANOVA), exponential regression and Pearson’s correlation were used to examine spatial differences, distance-decay relationships and associations between soot deposition and Σ16PAHs. Soot deposition decreased from 18.64 ± 1.12 mg m−2 day−1 at 100 m to 3.21 ± 0.42 mg m−2 day−1 at 1,000 m, compared with 1.18 ± 0.16 mg m−2 day−1 at the reference location. Σ16PAHs declined from 2,639.36 μg kg−1 at 100 m to 640.65 μg kg−1 at 1,000 m, compared with 257.84 μg kg−1 at the reference location. Phenanthrene, fluoranthene and pyrene were the dominant PAHs at 100 m, while benzo[a]pyrene reached 214.75 μg kg−1. BaP-TEQ decreased from 337.4 μg kg−1 at 100 m to 80.5 μg kg−1 at 1,000 m. Exponential regression showed strong distance-decay relationships for soot deposition (R² = 0.978) and Σ16PAHs (R² = 0.994), while soot deposition and Σ16PAHs were strongly correlated (r = 0.999). Four-ring PAHs accounted for approximately 40% of Σ16PAHs across the sampling locations. The findings demonstrate substantial spatial variation in soot and PAH deposition around the gas-flaring corridor and underscore the importance of environmental monitoring in surrounding communities.