Occurrence and partitioning of polyhalogenated carbazoles in seawater and sediment from East China Sea

Abstract

Polyhalogenated carbazoles (PHCZs) have received great concern due to their environmental persistence and potential dioxin-like toxicities. Their presence in the marine sediment had been well characterized, but limited studies had investigated their environmental behaviors in the marine environment. In this study, we collected paired seawater (n = 48) and surface sediment samples (n = 48) from East China Sea and analyzed for carbazole (CZ) and 11 PHCZs to investigate the occurrence and spatial distribution of CZ and PHCZs in seawater and sediment, as well as to explore the partitioning behaviors of CZ and PHCZs between seawater and sediment. In seawater samples, CZ and nine PHCZs were detected, with the concentrations of ∑PHCZs ranging from 0.21 to 11 ng/L (mean 2.7 ng/L). CZ (94%), 3-CCZ (89%), 1368-CCZ (65%), and 36-CCZ (57%) had relatively higher detection frequencies. Among PHCZs, 36-CCZ (mean 1.1 ng/L) had the highest mean seawater concentration, followed by 3-CCZ (0.51 ng/L) and 1368-CCZ (0.19 ng/L). In sediment, CZ and 11 PHCZs were detected, with the concentrations of ∑PHCZs ranged from 0.34 to 2.0 ng/g (mean 1.0 ng/g). CZ, 3-CCZ, 3-BCZ, 36-CCZ, 27-BCZ, and 36-BCZ were measurable in all sediment samples, and 36-CCZ was the predominant PHCZ (0.47 ng/g, 0.025–1.1 ng/g), followed by 1368-BCZ (0.16 ng/g, <LOD–0.29 ng/g) and 3-BCZ (0.11 ng/g, 0.016–0.33 ng/g). This study first calculated the field-based log Koc values for CZ and PHCZs in marine environment. CZ (mean 2.8, range 1.4–3.6) had the highest log Koc value, followed by 36-CCZ (2.7, 1.7–3.8), 1-B-36-CCZ (2.7, 2.3–3.1), and 36-BCZ (2.5, 2.2–2.9). The results of study may contribute to the better understanding of the environmental occurrence and behaviors of these chemicals in the marine environment.