Presence and Biotransformation of three Heteroaromatic Compounds Compared to an Aromatic Hydrocarbon

Occurrence, bioaccumulation and potential risk of polyhalogenated carbazoles in marine organisms from the East China Sea

As well-known emergent environmental contaminants, polyhalogenated carbazoles (PHCZs) have recently received increasing attention. In this study, we investigated the concentrations of carbazole (CZ) and PHCZs in 70 marine organisms from the East China Sea (ECS). CZ and 9-11 PHCZs were detected in organisms from the ECS, with concentrations in the range of 0.75-33 ng/g lipid weight, lw and 4.3-113 ng/g lw, respectively. Among the PHCZs, there were 3-4 major components in zooplankton, fish, shrimp, crabs, snails and shellfish, and the sum of these major components accounted for 59% to 67% of ∑PHCZs. The bioaccumulation potentials of 1,3,6,8-tetrachlorocarbazole (1368-CCZ) and 3-chlorocarbazole (3-CCZ) from water were observed. The logarithmic bioaccumulation factor (logBAF) values of the CZ and PHCZs increased significantly with increasing logK_OW values (R = 0.449-0.784, p < 0.01). The trophic magnification factor (TMF) values of the CZ, 9 PHCZs and ∑PHCZs were calculated to be 3.32, 1.87-4.06 and 2.36, respectively, indicating the potential biomagnification of the CZ and PHCZs in the zooplankton-shrimp-fish food web. The toxic equivalents (TEQs) of PHCZs in organisms from the ECS were in the range of 0.78-36 pg TEQ/g lw. Overall, for the first time, this study systematically examined the occurrence, bioaccumulation and potential risk of PHCZs in the marine food web of the East China Sea.

Quantitative determination of ultra-trace carbazoles in sediments in the coastal environment

Carbazole and some of its derivatives may possess dioxin-like toxicity and could be persistent in the environment, but information on their distribution and environmental fate is limited. This study developed and validated an ultra-trace targeted-analysis method for the determination of carbazole, 1,2-benzocarbazole, and 13 halogenated carbazoles in sediments from the river, coast, and North Sea. An 8-g sediment sample was extracted using accelerated solvent extraction combined with in-cell cleanup and analyzed using gas chromatography-tandem mass spectrometry. The method was sensitive and reliable with method detection limits ranging from 4.54 to 52.9 pg/g, and most of the quantification biases and relative standard deviations were <20 and <15%, respectively. Carbazole and 1,2-benzocarbazole were the predominant substances in the sediments (median 565 and 369 pg/g, respectively) followed by 3,6-dichlorocarbazole (median 196 pg/g). The detection frequencies of carbazole, benzo-, 3-chloro-, and 3,6-dichlorocarbazole were >75%, while those of 3,6-dibromo-, 1-bromo-3,6-dichloro-, and 1,8-dibromo-3,6-dichlorocarbazole were approximately 50%. Brominated carbazoles occurred more frequently in marine than river-influenced sediments, which could indicate halogenation after discharge into the river. This is the first study regarding these substances in coastal environments without apparent contamination history. The ubiquity and bioaccumulative potential of these substances needs to be considered.

Glutathione, glutathione S-transferase, and glutathione conjugates, complementary markers of oxidative stress in aquatic biota

Contaminants are ubiquitous in the environment and their impacts are of increasing concern due to human population expansion and the generation of deleterious effects in aquatic species. Oxidative stress can result from the presence of persistent organic pollutants, metals, pesticides, toxins, pharmaceuticals, and nanomaterials, as well as changes in temperature or oxygen in water, the examined species, with differences in age, sex, or reproductive cycle of an individual. The antioxidant role of glutathione (GSH), accompanied by the formation of its disulfide dimer, GSSG, and metabolites in response to chemical stress, are highlighted in this review along with, to some extent, that of glutathione S-transferase (GST). The available literature concerning the use and analysis of these markers will be discussed, focusing on studies of aquatic organisms. The inclusion of GST within the suite of biomarkers used to assess the effects of xenobiotics is recommended to complement that of lipid peroxidation and mixed function oxygenation. Combining the analysis of GSH, GSSG, and conjugates would be beneficial in pinpointing the role of contaminants within the plethora of causes that could lead to the toxic effects of reactive oxygen species.