Updated Polychlorinated Biphenyl Mass Budget for Lake Michigan

Abstract

This study revisits and updates the Lake Michigan Mass Balance Project (LMMBP) for polychlorinated biphenyls (PCBs) that was conducted in 1994-1995. This work uses recent concentrations of PCBs in tributary and open lake water, air, and sediment to calculate an updated mass budget. Five of the 11 LMMBP tributaries were revisited in 2015. In these five tributaries, the geometric mean concentrations of ∑PCBs (sum of 85 congeners) ranged from 1.52 to 22.4 ng L. The highest concentrations of PCBs were generally found in the Lower Fox River and in the Indiana Harbor and Ship Canal. The input flows of ∑PCBs from wet deposition, dry deposition, tributary loading, and air to water exchange, and the output flows due to sediment burial, volatilization from water to air, and transport to Lake Huron and through the Chicago Diversion were calculated, as well as flows related to the internal processes of settling, resuspension, and sediment-water diffusion. The net transfer of ∑PCBs is 1240 ± 531 kg yr out of the lake. This net transfer is 46% lower than that estimated in 1994-1995. PCB concentrations in most matrices in the lake are decreasing, which drove the decline of all the individual input and output flows. Atmospheric deposition has become negligible, while volatilization from the water surface is still a major route of loss, releasing PCBs from the lake into the air. Large masses of PCBs remain in the water column and surface sediments and are likely to contribute to the future efflux of PCBs from the lake to the air.

The Ins and Outs of Per- and Polyfluoroalkyl Substances in the Great Lakes: The Role of Atmospheric Deposition

“…To put these budgets in a broader context and compare them with well-known legacy chemicals, the wet deposition of the four chemicals combined to Lake Michigan was 104 ± 12.0 kg yr –1 which is lower than the value reported for all PBDEs in 2006 (250 ± 66 kg yr –1 ), and higher than that for PCBs (24.6 ± 3.1 kg yr –1 ) in 2015. It should be noted that also PBDEs and PCBs are the sum of 40 or more individual compounds …”

“…Each parameter was assigned an uncertainty, and errors were propagated, as previously described. 55 Complete equations and values for parameters are included in Text S4 and Tables S11–S14 .…”

Mechanistic insight into the Dehalococcoides-mediated reductive dechlorination of polychlorinated biphenyls

“…1 Although the production and usage of PCBs have been ceased for nearly four decades, substantial legacies of PCBs still reside in environment. Taking Lake Michigan as a recent example, the amount of PCBs remaining in the lake sediment (0-4 cm) and water is up to 13 400 AE 3 150 kg, 2 providing a nonnegligible and troublesome source of PCBs. The legacies of PCBs can be transferred into biota, triggering the population decline of marine mammals.…”

Carbonate Disequilibrium in the External Boundary Layer of Freshwater Chrysophytes: Implications for Contaminant Uptake

“…With diverse carbon acquisition mechanisms, ranging from photoautotrophy in all Synurophyceae to phagomixotrophy in many Chrysophyceae, these algal classes play an important role in determining the carbon flow through the food web, including in Canadian Shield water bodies that represent ∼50% of the world’s freshwater lakes . Several freshwater chrysophyte habitats are impacted by metals released from mining industries , and organic contaminants discharged from urban areas. , Anthropogenic eutrophication of freshwater systems as well as global change related-CO 2 increases and concomitant acidification can also affect the physiology and diversity of chrysophytes . Such pH changes may further impact the uptake and toxicity of several inorganic and hydrophobic contaminants in phytoplankton. − For freshwater phytoplankton, chemical reactions in the phycosphere (external boundary layer) surrounding cells rather than those in the well-mixed bulk phase dictate the overall interactions between algae and their external aquatic medium.…”

“…2 Several freshwater chrysophyte habitats are impacted by metals released from mining industries 3,4 and organic contaminants discharged from urban areas. 5,6 Anthropogenic eutrophication of freshwater systems as well as global change related-CO 2 increases and concomitant acidification 7 can also affect the physiology and diversity of chrysophytes. 8 Such pH changes may further impact the uptake and toxicity of several inorganic and hydrophobic contaminants in phytoplankton.…”