Abstract
Water quality in rural areas is affected adversely by build-up of traffic-generated organic compounds on road surfaces, leading to their presence in water runoff and sediments. Characterising these compounds is a first step in developing measures for the removal of such pollutants from water courses. In this study, liquid-liquid extraction of water samples from several rivers and surface run-off enabled quantification of major PAHs. Soxhlet extraction of sediment samples was followed by clean-up of samples using column chromatography. The PAHs were quantified by gas chromatography. In water and sediment samples, 6 PAHs were identified and quantified. In river water samples, individual PAH levels ranged between 0.1 µg/. and 137 µg/., while in sediment samples levels ranged between 17.9 µg/kg and 9870 µg/kg. For surface run-off, levels ranged between 0.6 µg/. and 2 500 µg/. for water samples and between 112 µg/kg and 34 400 µg/kg for sediment samples. Total levels of PAHs in sediment samples were relatively high (111.6 to 61 764 µg/kg) compared to those in water from both river and surface run-off (29.2 to 3 064.8 µg/.), and PAH levels in surface runoff were much higher than in river waters, implicating tarred roads and parking lots as main point sources of PAHs. PAH ratios also indicate that the PAH content of runoff and sediment is more likely due to pyrogenic sources, i.e. vehicle emissions, although petrogenic sources (mainly oil spills) also play an important role. Toxic Equivalence Quotient (TEQ) values in river and runoff waters ranged from 0.10 to 4.03 µg/. and for sediments the TEQ ranged from 0.50 to 272.23 µg/kg. These results are of concern, as the calculated TEQ is likely to be an underestimate of the actual TEQ, since only 6 PAHs with relatively low toxicities were analysed. Long droughts and low rainfall, and washing of automobiles in and near the rivers are important factors which may have contributed to the observed levels of PAHs in both river water and sediments.Keywords: Polycyclic aromatic hydrocarbon, river water, runoff, sediment
Highlights
The toxicity of polycyclic aromatic hydrocarbons (PAHs) and their widespread distribution has led to more interest in the presence of these compounds in the aquatic and terrestrial environment
The distribution of PAHs in several samples, especially runoff and sediment collected near commercial areas (Table 6)
The highest total PAH value was obtained from a Univen parking lot surface runoff sediment sample (61 754 μg/kg); the lowest water PAH value (38.2 μg/kg) was obtained from the Luvuvhu River, in a rural area upstream from Thohoyandou
Summary
The toxicity of polycyclic aromatic hydrocarbons (PAHs) and their widespread distribution has led to more interest in the presence of these compounds in the aquatic and terrestrial environment. Many studies have been done in developed countries (e.g., Crystal and Foster, 1991; Maldonado et al, 1999), but in South Africa few studies have been conducted to determine the presence and levels of PAHs in the environment (Butler and Sibbald, 1986). Nieuwoudt et al (2011) extensively investigated soils and sediments collected from central South Africa, targeting industrial, residential, and agricultural areas. The total concentration of PAHs was found to range between 44 and 39 000 ng/g with pyrogenic processes the most likely sources. PAH levels were in the same range as levels reported from other countries
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
