Assessment of Polycyclic Aromatic Hydrocarbon in Soils and Sediments in Onitsha area, Southeastern, Nigeria

Abstract

Polycyclic Aromatic Hydrocarbons (PAHs) are environmental pollutant that can impair environmental quality and health, and consequent ecological risk. The study was aimed at determining the concentration and environmental status of PAHs in the soils and sediments of Onitsha metropolis and identify their probable source(s). Sixty samples of soils (44) and sediments (16) were collected for the study. Extraction of organics was facilitated by infusing the samples with dichloromethane and subjected to ultrasonic agitation. The analyses of the PAHs were undertaken using gas chromatography/mass spectrometry (GC/MS).Thirteen PAHs were detected in soils and sediments exhibiting varying concentration across several sampling locations. The concentration range (µg/kg) of the 13 identified PAHs in soil and sediments were Fluorene 0.00 - 122.2and 1.7-31.1; Anthracene, 0.0 – 55.3and 1.7 - 46.0; Phenathrene 1.0 – 2045.8and 22.2 – 266.2; Fluoranthene, 1.0 – 483.7and 13.4 – 602.9; Pyrene, 3.7 – 533.4and 14.1 – 531.8; Benzo [k]fluoranthene 1.0 – 166.5; 4.0 – 163.5; Benzo[a]anthracene, 1.0 - 222.0; 5.6 – 298; Benzo[b]fluoranthene, 1.1 – 502.6 and 14.1 – 452.9; Dibenz[ah]anthracene 1.0 – 33.4 and 1.0 37 0; Chrysene, 1.0 – 426.4and 10.0 – 385.6; Benzo [a] pyrene 1.0 – 502.6and 12.9 – 514.9 Benzo[ghi]perylene, 1.0 – 557.8and 14.9 – 326.0; Indeno[123-cd]pyrene 1.0 – 412.2and 1.0 – 37.0, respectively The fractional concentration of PAHs and Total Organic Carbon (TOC) analysed using Principal Component Analyses revealed different partitioning of the TOC and PAHs in soils and sediments. This indicated distinct sourcing of the TOC and PAHs in the environmental media. Relatively higher concentrations of PAHs were found in environment characterized by combustion activities such as waste dump sites, Mechanic and Metal Works environments. Pyrogenic (combustion) activities were indicted as the main contributors of the PAHs to the soils and sediments.