This work continued investigations of polyhalogenated carbazoles (PHCZs) in sediments of the Laurentian Great Lakes. A total of 77 Ponar grab samples plus approximately 300 segments from 12 sediment cores from Lakes Erie and Ontario were analyzed for carbazole (CZ) and 26 PHCZs. CZ is widespread in sediments of all five Great Lakes, particularly in Lake Erie where it has accumulated >100 tonnes, which is similar to that of total polychlorinated biphenyls. Among the 26 PHCZs, 3-bromo- (3-BCZ) and 3-chloro- (3-CCZ) carbazoles exhibited the greatest mass loads in Lakes Ontario and Erie, although their stratigraphic sediment records suggest peaking of input occurred before 1980 and are now decreasing. Of emerging concern are several dibromocarbazoles, which exhibit rapid increases in net fluxes to sediment since the 1980s. Accumulation of PHCZs that are considered to be of natural origin decreases in an eastward and southward transect across the region, opposite to the trend for those that are predominantly of human activity related origin. The dependences on water depth and sediment organic matter content differ among PHCZs and their categories. Results presented here demonstrate the inter-related influences of natural processes and human activities on occurrences, fates, and dispositions of PHCZs and likely other organohalogens in the Great Lakes.
Bibliographical noteFunding Information:
This research was part of the Great Lakes Sediment Surveillance Program (GLSSP) funded by a Cooperative Agreement from the U.S. EPA Great Lakes Restoration Initiative with Assistance No. GL-00E00538. Shanshan Zhou and Huan He received funds from National Natural Science Foundation of China (grant nos. 41877494 and 41671493) and their institutions in China. The authors sincerely thank Dr. Tian Lin of College of Marine Ecology and Environment, Shanghai Ocean University, for his contribution to this work. Jiehong Guo was partially supported by Predoctoral Fellowships from the Institute for Environmental Science and Policy at the University of Illinois Chicago (UIC). An Li was partially supported by the Samuel and Catherine Epstein Professorship at UIC School of Public Health. Prof. Giesy was supported by the Canada Research Chair program and a Distinguished Visiting Professorship in the Department of Environmental Sciences at Baylor University, Waco, Texas. The authors thank the crew of R/V Lake Guardian for their assistance during sampling. They acknowledge the participation in sediment sampling expeditions by Valerie Blomgren, Zhuona Li, Prabha Ranasinghe, Soheil Hosseini, Anja Vogt, Admasu Wondmagegn, Benjamin Alsip, Garry Codling, Lisa Duran, Changmin Long, and Yumin Su.
- mass spectrometry
- natural and synthesized chemicals
- pollutants of emerging concerns
- polyhalogenated carbazoles
- the Great Lakes