Non-negligible Polyhalogenated\nCarbazoles in Arctic\nSoils and Sediments: Occurrence, Target and Suspect Screening, and\nPotential Sources

The presence of polyhalogenated carbazoles (PHCZs), which\nare emerging\nas dioxin-like contaminants, in remote polar regions has not been\nreported. This study investigated 11 target PHCZs (Σ<sub>11</sub>PHCZs) and 25 unknown PHCZs (Σ<sub>25</sub>UNPs) in soil and\nsediment samples collected from Ny-Ålesund in the Arctic. The\nfindings revealed that Σ<sub>11</sub>PHCZs concentrations reached\n165.6 ng/g dry weight (dw), with 3,6-dichlorocarbazole and 3-chlorocarbazole\nbeing the predominant congeners. The Σ<sub>25</sub>UNPs concentrations\nranged from 1.4 to 92.4 ng/g dw (median: 17.0 ng/g dw), primarily\ncomprising a 1,3,6,8-tetrabromocarbazole isomer. The sediment contained\n∼6 times more Σ<sub>25</sub>UNPs than Σ<sub>11</sub>PHCZs. Long-range atmospheric transport, oceanic transport, and human\nactivity can potentially affect soils and sediments concurrently.\nFor the first time, halogen substitution patterns in PHCZs, including\nClI, ClI<sub>2</sub>, and ClI<sub>3</sub>, were detected in soil and\nsediment. Using the toxic equivalent (TEQ) approach, the potential\ntoxic effects linked to the target PHCZ levels were assessed. The\nTEQ<sup>PHCZs</sup> in Arctic soils and sediments indicated low risk,\nranging from 8.0 × 10<sup>–3</sup> to 17 pg TEQ/g dw (median:\n2.8 pg TEQ/g dw) and 0.1 to 0.4 pg TEQ/g dw (median: 0.3 pg TEQ/g\ndw), respectively. This study marks the first report on the occurrence,\ncomposition, sources, and potential risks posed by PHCZs in the Arctic\nregion.