Abstract
The fate of persistent organic pollutants in sea ice is a poorly researched area and yet ice serves as an important habitat for organisms at the base of the marine foodweb. This study presents laboratory-controlled experiments to investigate the mechanisms governing the fate of organic contaminants in sea ice grown from artificial seawater. Sea ice formation was shown to result in the entrainment of chemicals from seawater, and concentration profiles in bulk ice generally showed the highest levels in both the upper (ice–atmosphere interface) and lower (ice–ocean interface) ice layers, suggesting their incorporation and distribution is influenced by brine advection. Results from a 1-D sea ice brine dynamics model supported this, but also indicated that other processes may be needed to accurately model low-polarity compounds in sea ice. This was reinforced by results from a melt experiment, which not only showed chemicals were more enriched in saltier brine, but also revealed that chemicals are released from sea ice at variable rates. We use our results to demonstrate the importance of processes related to the occurrence and movement of brine for controlling chemical fate in sea ice which provides a pathway for exposure to ice-associated biota at the base of the pelagic food web.
Highlights
Persistent organic pollutants (POPs) comprise a large group of mainly synthetic, toxic chemicals that have long environmental half-lives and are subject to long-range transport by global atmospheric and oceanic circulation currents.[1]. These chemicals are present in the marine environment of polar regions and have been shown to bioaccumulate and biomagnify in Arctic food webs[2,3] The role of snow and sea ice in the fate and transfer of both older “legacy” and contemporary “emerging” chemicals to biological systems has not been well studied despite their occurrence in Arctic seawater
While we can not state conclusively that this factor did not affect the distribution of chemicals in our experiments, our results suggest that another process(es) currently not described by the physics incorporated within the brine dynamics model may be at play
The results show that the highest mass of the most hydrophobic chemicals (PCB-28, chlorpyrifos, BDE-47, BDE-99) was present in the final meltwater fraction (MWF4), unlike NaCl which has the lowest mass in MWF4
Summary
Persistent organic pollutants (POPs) comprise a large group of mainly synthetic, toxic chemicals that have long environmental half-lives and are subject to long-range transport by global atmospheric and oceanic circulation currents.[1] As such, these chemicals are present in the marine environment of polar regions and have been shown to bioaccumulate and biomagnify in Arctic food webs[2,3] The role of snow and sea ice in the fate and transfer of both older “legacy” and contemporary “emerging” chemicals to biological systems has not been well studied despite their occurrence in Arctic seawater. As the Arctic environment is rapidly changing, there is a rising motivation to understand the biogeochemical cycling of these toxic chemicals in sea ice
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