Impact of land-use types on the distribution and accumulation of polycyclic aromatic hydrocarbons in soil from Sagamu Town, Southwestern Nigeria

Abstract

Man-made activities such as urbanization and expansion of agricultural activities are increasingly changing our landscapes. An evaluation  of the effects of land use on soil standards is critical for the sustainable management of human health and its surroundings.  This study examines the impact of land use types on the abundance and distribution of Polycyclic Aromatic Hydrocarbons (PAHs) in soil  as affected by three different land environments; Petrol Stations (NNPC), FarmLand, and Auto–Mechanic Villages. A focus on the  concentrations and spatial distribution of PAHs in soil samples collected from each land-use type in Sagamu Township and its surroundings, was subject to a generalized assessment while identifying important contaminating factors in the soil. Soil analysis  confirmed that Auto-Mechanic Village constitutes the highest contributor of PAH and increased concentrations are detected from this  land-use type. Significantly, the Petrol Station (NNPC) also showed a high PAH distribution but was lower than the Auto mechanic village.  The levels of PAHs (∑7PAHs) obtained in NNPC, Mechanic Village, and FarmLand are 0.054 mg/kg 0.073 mg/kg, and 0.0328 mg/kg respectively. The highest values of PAHs concentration were returned from Mechanic Village soil samples and the lowest value was  obtained from the FarmLand samples. This trend of PAH prevalence was consistent with the number of rings inside the structure,  apparent at each sampling site and across the whole study area. The Σ5- 6 ring PAHs dominate at a concentration of 0.0481 mg/kg (50%  of total PAHs). Σ2–3ring PAHs show 0.0257 mg/kg, percent abundance 27%. In contrast, there are scarce occurrences of Σ4 ring PAHs, of  which the lowest values reach up to 0.0223 mg/kg (23%). The findings highlight the relevance of accounting for co-exposure to different  land-use-type when assessing the risk of soil contamination for human health and offer useful insights to policymakers, environmental  regulators, and land-use planners.