Abstract
The existence of polycyclic aromatic hydrocarbons (PAHs) in the environment is a significant cause of concern due to their persistence, toxicity, and wide-ranging pollution. This study aimed to assess the levels of PAHs present in water and sediment samples collected from the Klip River in Johannesburg, South Africa. The PAHs in water and sediment samples were extracted by employing liquid-liquid extraction (LLE) and optimised microwave-assisted extraction (MAE), respectively. A gas chromatography-flame ionisation detector (GC-FID) was used as the analytical technique of choice for the quantification of the sixteen (16) PAHs in water and sediment samples collected from the Klip River. The concentrations of PAHs obtained in sediment samples were higher than those detected in water samples. The total concentration of PAHs detected in sediment samples collected from the Klip River in nine selected sites ranged between 1.46 to 7.41 mg/kg, which was higher than those detected in water samples ranging between 0.000579 to 0.00502 mg/L. In both samples, high molecular weight (HMW) PAHs were found to be in higher levels than the lower molecular weight (LMW) PAHs, suggesting the availability of pyrogenic activities along the study sites. The accuracy and effectiveness of the PAHs extraction methods were determined by assessing the percentage recoveries of PAHs in water samples spiked with known amounts of standards and certified reference material (CRM) for sediment samples. The obtained percentage recoveries for MAE ranged from 80.7 to 117.8%, whereas those for LLE ranged from 78.3 to 117% For source identification in sediment samples, the diagnostic ratio was employed, showing that detected PAHs were from petrogenic, pyrogenic, and combustion of petroleum sources. The conducted toxicity study using the zebrafish embryo test indicated that sediment samples from the Klip River are highly contaminated compared to water samples, resulting in high mortality, a low hatch rate, and high malformations in zebrafish embryos exposed to them, which further indicates the risk experienced by water, the environment, biotic animals, and humans using the river for any use. Hence, there is a need for the establishment of research projects intending on detecting the level of contaminants in the river to control and sustain both water and the environment.