Determination and Distribution of Polycyclic Aromatic Hydrocarbons in Rivers, Sediments and Wastewater Effluents in Vhembe District, South Africa.

Oluwaseun Popoola,John Odiyo,Titus Msagati,Joshua Edokpayi

doi:10.3390/ijerph13040387

Abstract

Polycyclic aromatic hydrocarbons are very toxic and persistent environmental contaminants. This study was undertaken to assess the concentrations and possible sources of 16 PAHs (Polycyclic aromatic hydrocarbons) classified by the United State Environmental Protection Agency as priority pollutants in water and sediments of the Mvudi and Nzhelele Rivers. Effluents from Thohoyandou wastewater treatment plant and Siloam waste stabilization ponds were also investigated. Diagnostic ratios were used to evaluate the possible sources of PAHs. PAHs in the water samples were extracted using 1:1 dichloromethane and n-hexane mixtures, while those in the sediment samples were extracted with 1:1 acetone and dichloromethane using an ultrasonication method. The extracts were purified using an SPE technique and reconstituted in n-hexane before analyses with a gas chromatograph time of flight—mass spectrometer. The results obtained indicate the prevalence of high molecular weight PAHs in all the samples. PAHs concentrations in water and sediment samples from all the sampling sites were in the range of 13.174–26.382 mg/L and 27.10–55.93 mg/kg, respectively. Combustion of biomass was identified as the major possible source of PAHs. Effluents from wastewater treatment facilities were also considered as major anthropogenic contributions to the levels of PAHs found in both river water and sediments. Mvudi and Nzhelele Rivers show moderate to high contamination level of PAHs.

Highlights

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment and are part of numerous organic contaminants that are persistent in the environment, have long transport potential and can cause adverse environmental effects [1,2]
16 PAHs recommended by the United State Environmental Protection Agencies (US EPA) were investigated in this study but only 10 of them were determined in all of the sampling sites during the course of this study (Table 1) while the other 6 were below detectable limits
The levels of PAHs determined in Mvudi and Nzhelele River sediments range between 0.266 and 21.60 mg/kg and 0.206 and 13.71 mg/kg, respectively

Summary

Introduction

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment and are part of numerous organic contaminants that are persistent in the environment, have long transport potential and can cause adverse environmental effects [1,2]. Some of them are susceptible to dispersion on a global scale because, in addition to having environmental persistence, they are “semi-volatile”, i.e., under environmental conditions they move between the atmosphere and the earth’s surface in repeated, temperature-driven cycles of deposition and volatilisation [3,4]. PAHs are truly multimedia contaminants which occur in all parts of the environment: atmosphere, inland and sea waters, sediments, soils and vegetation [2,3]. Res. Public Health 2016, 13, 387; doi:10.3390/ijerph13040387 www.mdpi.com/journal/ijerph

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Conclusion