Occurrence and probabilistic risk assessment of PAHs in water and sediment samples of the Diep River, South Africa

Abstract

This study investigated the levels of polycyclic aromatic hydrocarbons (PAHs) in water and sediment samples of the Diep River freshwater system of Western Cape Province, South Africa. A solid-phase extraction -gas chromatography -flame ionisation detection (SPE-GC-FID) method was utilised to simultaneously determine the 16 United States Environmental Protection Agency (US EPA) listed priority PAHs in water and sediment samples. The seasonal averages of individual PAH detected at the studied sites, ranged between not detected (Nd) and 72.38 AE 9.58 μg/L in water samples and between Nd and 16.65 AE 2.63 μg/g in the corresponding sediment samples. The levels of PAHs measured in water and sediment samples were subjected to probabilistic risk assessment to predict the possibility of regulatory values being exceeded. The average percentage exceedence of 63.26 was obtained for PAHs in water samples of the Diep River, while the corresponding average percentage exceedence obtained for sediment sample was 63.71. Sufficient exposure of humans and aquatic organisms to the exceedance levels obtained, would cause adverse health effect.

The impact of informal settlement on water quality of Diep River in Dunoon

“…This is because the wet season was in winter, while the dry season was in summer. The temperature results were slightly different from those in a previous study of the Diep River conducted by Awe in which, for the four seasons, the average temperature range was 14.0 and 24.2 °C (Awe et al 2020), while the range in this study was between 15.8 and 19.5 °C. The slight temperature difference could be attributed to the fact that the samples were taken on different days and times.…”

“…The pH results in this study were slightly higher than those obtained by Awe in a previous study conducted in Diep River, even though they were both within the recommended limits for domestic, recreational, and agricultural water use. The average water pH range recorded in Awe's study was 7.16-7.98 (Awe et al 2020), whereas the pH range in this study was 7.4-8.4.…”

“…In a study conducted by Awe, the seasonal salinity values recorded at the different Diep River study sites ranged from 915 to 5231 mg/L, while the seasonal range in this study was from 1.3 to 9.2 psu (equivalent to 1300-5300 mg/L) (Awe et al 2020). In Awe's study, most of the seasonal salinity values recorded at the studied Diep River sites were higher than the recommended acceptable value of less than 1000 mg/L for the protection of freshwater life.…”

“…This trend may be attributed to an increase in the concentration of organic and inorganic materials and salts because of runoff from domestic and other human activities into the river during the wet season, discharges by the feeder streams, and industrial effluents (Anhwange et al 2012). A similar study by Awe showed that electrical conductivity values at the Milnerton Woodbridge (DC) site were higher than the acceptable range of 0-1500 µS/cm set by the Department of Water and Sanitation of South Africa, whereas the Table Bay Nature Reserve (DA) and Theo Marais (DB) sites were below 1500 µS/cm in all seasons except spring (Awe et al 2020). The possible contributing factors to the high EC values were wastewater runoff into the rivers, river flows, and tidal waves.…”

Characterization of River Sediments in Loja-Ecuador

“…Other sectors exceed the regulations, but the values are associated with the background. Great care must be taken to consume aquatic life and plants that accumulate the metal [28]. In addition, it can produce a decrease in the properties of the soil when used for agriculture [29].…”