Non-negligible Polyhalogenated Carbazoles in Arctic Soils and Sediments: Occurrence, Target and Suspect Screening, and Potential Sources

The presence of polyhalogenated carbazoles (PHCZs), which are emerging as dioxin-like contaminants, in remote polar regions has not been reported. This study investigated 11 target PHCZs (Σ₁₁PHCZs) and 25 unknown PHCZs (Σ₂₅UNPs) in soil and sediment samples collected from Ny-Ålesund in the Arctic. The findings revealed that Σ₁₁PHCZs concentrations reached 165.6 ng/g dry weight (dw), with 3,6-dichlorocarbazole and 3-chlorocarbazole being the predominant congeners. The Σ₂₅UNPs concentrations ranged from 1.4 to 92.4 ng/g dw (median: 17.0 ng/g dw), primarily comprising a 1,3,6,8-tetrabromocarbazole isomer. The sediment contained ∼6 times more Σ₂₅UNPs than Σ₁₁PHCZs. Long-range atmospheric transport, oceanic transport, and human activity can potentially affect soils and sediments concurrently. For the first time, halogen substitution patterns in PHCZs, including ClI, ClI₂, and ClI₃, were detected in soil and sediment. Using the toxic equivalent (TEQ) approach, the potential toxic effects linked to the target PHCZ levels were assessed. The TEQ^PHCZs in Arctic soils and sediments indicated low risk, ranging from 8.0 × 10^-3 to 17 pg TEQ/g dw (median: 2.8 pg TEQ/g dw) and 0.1 to 0.4 pg TEQ/g dw (median: 0.3 pg TEQ/g dw), respectively. This study marks the first report on the occurrence, composition, sources, and potential risks posed by PHCZs in the Arctic region.