Spatial and Temporal Trends of Polyhalogenated Carbazoles in Sediments of Upper Great Lakes: Insights into Their Origin

Abstract

Polyhalogenated carbazoles (PHCZs) have been increasingly detected in the environment. Their similarities in chemical structure with legacy pollutants and their potential toxicity have caused increasing concern. In this work, 112 Ponar grab and 28 core sediment samples were collected from Lakes Michigan, Superior, and Huron, and a total of 26 PHCZs were analyzed along with unsubstituted carbazole using gas chromatography coupled with single- or triple-quadrupole mass spectrometry. Our results show that the total accumulation of PHCZs in the sediments of the upper Great Lakes is >3000 tonnes, orders of magnitude greater than those of polychlorinated biphenyls (PCBs) and decabromodiphenyl ether (BDE209). The 27 individual analytes differ in spatial distribution and temporal trend. Our results showed that PHCZs with substitution patterns of -Br, -ClBr, or having iodine, were more abundant in sediment of Lake Michigan deposited before 1900 than those deposited more recently, implying a natural origin. Some "emerging" PHCZs have been increasingly deposited into the sediment in recent decades, and deserve further environmental monitoring and research. Other PHCZs with low halogen substitution may form from in situ dehalogenation of PHCZs having more halogens. Anthropogenic sources of PHCZs may exist, particularly for the emerging and low molecular mass congeners.

mRNA Expression and Biomarker Responses in Perch at a Biomonitoring Site in the Baltic Sea – Possible Influence of Natural Brominated Chemicals

“…For the brominated carbazoles, the origins are more unclear with the anthropogenic origin, including sources such as the production of dyes, aluminum industry, rubber, coal combustion and more (Guo et al, 2014;Fromme et al, 2018). However, it has been suggested that carbazoles also have natural origins and seem to dominate in sediment from the great lakes (Barbosa et al, 2014;Guo et al, 2017). Since Kvädöfjärden is located away from large anthropogenic activities, it is likely that the major contribution of the carbazoles are natural sources in that area.…”

“…It would be of great interest to perform quantitative measurements of the brominated carbazoles and indoles retrospectively in the perch from Kvädöfjärden. This would be a very important task for the future, as it is likely that historic release in the environment of these groups of halogenated compounds are buried in sediments (Guo et al, 2014(Guo et al, , 2017. In addition, it is likely that there is an on-going release of these compounds into the environment from current anthropogenic and/or natural activities (Guo et al, 2014(Guo et al, , 2017Fromme et al, 2018;Wu et al, 2018).…”

A review of persistent organic pollutants: dioxins, furans, and their associated nitrogenated analogues

“…This underscores what scientific findings have stated as notorious 'super poisons' distributed in the environment. The toxicity of halogenated heterocyclic compounds for example halogenated carbazoles to biota and humans have drawn a lot of interest [32]. It is important to note that halogenated carbazoles are structurally similar to polychlorinated dibenzo-p-dioxin and halogenated dibenzofurans; therefore they are believed to be extremely toxic because of their dioxin-like characteristic behaviour attributed to similarity in their molecular conformations [32].…”

“…The toxicity of halogenated heterocyclic compounds for example halogenated carbazoles to biota and humans have drawn a lot of interest [32]. It is important to note that halogenated carbazoles are structurally similar to polychlorinated dibenzo-p-dioxin and halogenated dibenzofurans; therefore they are believed to be extremely toxic because of their dioxin-like characteristic behaviour attributed to similarity in their molecular conformations [32]. Polyhalogenated carbazoles (PHCs) which has been established to be non-degradable in the soil [73] display toxicities similar to those of dioxins and furans and are precursors for carcinogenesis, developmental defects and lowered immunity in animals [92].…”

“…Heterocyclic compounds of the polycyclic heteroaromatic group are well known environmental pollutants that are discriminately abundant in the environment and whose source and environmental pathways are known to be mainly anthropogenic as well as from combustion activities [73,86]. Nitrogenated aromatic heterocyclic compounds generally are components of crude oil and include carbazole and dibenzopyrroles among other heterocycles of toxicological significance [32]. These compounds are remarkable environmental pollutants because they emit oxides of nitrogen (NOx) which have the ability to deplete the ozone layer in addition to causing acid rains [56].…”