Occurrence of organic pollutants: pahs in water bodies around kelanitissa and kerawalapitiya power plants in Sri Lanka

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are a group of organic compounds with more than one benzene ring formed due to natural processes such as forest fires and anthropogenic activities. These ubiquitous contaminants have gathered an interest due to their toxicity and carcinogenic activity. Exposure to PAHs has also been linked with cancer, cardiovascular disease and poor fetal development. PAHs are considered as persistent organic pollutants because of their stable chemical structure and inherent resistance to decomposition. In this study, the water bodies near two diesel fueled power plants in Sri Lanka i.e., Kerawalapitiya and Kelanitissa were selected to determine the presence of PAHs in surface water and its sediment. In the preliminary sampling rounds, the presence of PAHs were identified. With increased sample size, three sampling rounds were carried out. In addition to water and sediment from Hamilton canal and Sebastian canal, water samples from wells near both power plants were analyzed. PAHs in water samples were extracted to dichloromethane and analyzed by HPLC with UV-DAD (254 nm) and HPLC- FLD (excitation at 250 nm, emission at 410 nm). Sediment samples were pretreated before the analysis and then, PAHs were extracted to methanol by ultrasonication. The presence of low, medium and high molecular weight PAHs in water and sediment samples obtained from both sites were detected. Total concentration of PAHs in surface water samples obtained from Sebastian canal during rainy season (April 2015), dry season (July 2015) and rainy season (June 2016) were 0.11-1.71 μg/L, 2.36-14.68 μg/L and 6.88 μg/L - 10.05 μg/L, respectively. Furthermore, PAH content in water samples obtained from Hamilton canal during rainy season (April 2015), dry season (July 2015) and rainy season (April 2016) were 0.16-2.74 μg/L, 11.06- 54.89 μg/L and 5.35 - 7.79 μg/L, respectively. Well water samples obtained from Kelanitissa (W1) and Kerawalapitiya (W3) showed the presence of high amounts of BaP (0.025 μg/L) and BkF (0.339 μg/L) respectively which are higher than the guideline values for BaP (0.01 μg/L) and BkF (0.1 μg/L) according to European Unions’ drinking water standards. The total PAH amount in surface water in both sites were higher in dry season than that of in rainy season. This may due to accumulation of PAHs over the time in water bodies around diesel fueled power stations during dry seasons due to lack of water flow. By investigating more dry and rainy seasons, an accumulation trend can be identified to address the seasonal variation of PAHS in water bodies.