Comparison of Ultra-Sonication and Microwave Extraction Followed by Filtration or Filtration and Solid-Phase Extraction Clean-Up for PAH Determination from Sediment and Sludge: Human Health and Ecological Risk Assessment

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are compounds originating from pyrogenic and petrogenic sources, which increases their potential introduction into the environment and possible exposure to humans. PAHs have been identified as compounds of concern due to their environmental persistence and toxicity to living organisms, leading to harmful health effects. As a consequence, the South African government (The Department of Water and Sanitation) has set national norms and standards for the assessment of waste for landfill disposal through the National Environmental Management: Waste Act, 2008 (NEMWA) license (Act No. 59 of 2008). This study therefore evaluated the concentrations, origin sources, human health and ecological risk of PAHs in sediment and sludge samples, which is a requirement by the South African government. The PAHs were determined using ultrasonic extraction (UE) and microwave-assisted extraction (MAE), followed by filtration, or filtration and clean-up with solid-phase extraction (SPE). The results obtained indicated that both methods can be used for the extraction of PAHs with relative accuracy and sensitivity. However, higher concentrations were obtained with F + SPE-cleaned samples (95.96–926.0 µg/kg) compared to filtered samples (21.61–380.6 µg/kg), with pyrene showing dominance over all other PAHs. The detected concentrations indicated that the PAHs were of petrogenic origin. These concentrations are currently within the total acceptable concentration levels of 5.0 × 104 µg/kg as prescribed by the NEMWA standards for sludge and sediments. However, the concentration above the effective medium range in river sediments revealed potential toxic effects to aquatic organisms. The ILCRderm values suggested a very high potential risk of cancer through dermal exposure to the inhabitants of the area. These findings indicate that continuous monitoring of these compounds is of paramount importance as the study area is not entirely safe for use even for recreational purposes.