Spatial distribution, source identification, and risk assessment of polychlorinated organic pollutants (PCDD/Fs and DL-PCBs) in the sediments of the largest urban water supply area (Iznik lake) in the Marmara region, Bursa, Türkiye.

[Display omitted] • Congeners of PCDD/Fs and DL-PCBs were examined in the sediments of Iznik lake. • PCB 118, PCB 105 and Hepta – Octa CDD/Fs are the dominant in the sediments. • Sediment close to industrial companies has the highest amount of pollutant. • Dioxin-like toxicity levels of sediments are higher than threshold of 0.85 pg TEQ/g. • Dioxin-like (PCDD/Fs and DL-PCBs) concentrations do not exceed the tolerable daily intake value. Iznik lake is the biggest lake in the Marmara region, which is the most industrialized and populated area of Türkiye. The lake is one of Türkiye's most important water supply areas and is located nearby the Iznik district of Bursa, with a population of about 45,000. It is being used for irrigation and fishery production, but not for drinking water. In this paper, the distribution, pollution source, and risk assessment of polychlorinated dibenzodioxins/furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) in the surface sediments of Iznik lake and streams (both flowing to and flowing from the lake) were investigated. Six surface sediments collected from the lake and four surface sediments collected from the streams were analyzed in high-resolution gas chromatography-mass spectrometry (HR/GC–MS) system in accordance with EPA 1613 and EPA 1668 methods. The concentration ranges of the ∑PCDD/Fs is 21.4 pg/g d.w. (inside the lake (IZ-6)) – 54.5 pg/g d.w. (Gülayağı stream (IZ-8)) and ∑DL-PCBs is 13.5 pg/g d.w. (inside the lake (IZ-3)) – 46.3 pg/g d.w. (Olukdere (IZ-7)) respectively, with 2.68 pg TEQ/g d.w. on average. The results showed that the high chlorinated (Hepta – Octa CDD/Fs) dioxins/furans and pentachlorinated PCBs (PCB 118 and 105) are dominant in the sediments. A detailed assessment of PCDD/F congener profiles observed in the lake sediments speculated that the wastewater discharges to the lake could be the main pollution source, while other sources such as open burning activities, runoff of pesticide residues from agricultural areas and atmospheric deposition may have some contribution also. The health risk assessment performed for polluted sediment demonstrated that, in the worst case, dioxin-like (PCDD/Fs and DL-PCBs) concentration was a total intake of 0.37 pg TEQ/kg body weight/day, no exceeds the tolerable daily intake amount, where fish consumption accounts for nearly all of the total intake. [ABSTRACT FROM AUTHOR]