Dissertation Abstract

Remote open oceans were traditionally considered as sinks of persistent organic pollutants (POPs) such as industrial chemicals (PCBs) and organochlorine pesticides (OCPs). In the context of reduced primary emissions and global warming, previous polluted reservoirs (soil, large water bodies, and glaciers) may act as secondary sources returning these POPs back to air and oceans. It was hypothesized that biogeochemical activities associated with phytoplankton in the water column would lead to the coupling of air-plankton systems to draw down the lipophilic POPs from the overlying atmosphere, similar to the biological pump taking up CO2 from air during phytoplankton blooms and then depositing it to the deep ocean. It has been found that POPs accumulate to high levels in apex predators (whales and polar bears). To fully understand how POPs biomagnify along the food web, it is important to quantify the transfer of POPs from sediments and water to the base of food webs. This dissertation research was conducted in three remote oceans to verify these hypotheses. 1) Air and water samples were collected simultaneously on R/V Revelle in the N. and S. Pacific for POPs analysis. Results suggest that the Pacific was acting as a secondary source returning PCBs back to the air. This was the first work documenting the open ocean as a secondary PCB source. 2) Air, water, and zooplankton samples were collected simultaneously during the North Atlantic Bloom in 2008 (NAB08) in a relatively small area south of Iceland. The POPs measurement showed dissolved lipophilic OCP remained constant with time as the bloom evolved. Also, OCPs were not being drawn from air to water during the bloom as previously hypothesized. Further it suggested that the Arctic was a source of higher concentrations of hexachlorocyclohexanes (HCHs) and both the atmospheric and oceanic transport would bring HCHs to the lower latitudes. Last, the measurements indicated that equilibrium partitioning governed the transfer of POPs from water into Calanus finmarchicus. An Eulerian box model was developed and used to further explore the fate of POPs during the bloom. Biogeochemical processes considered included air-water exchange, partitioning to particulate organic carbon (POC) and sinking POC, and biogeochemical degradation. Modeling results demonstrated that partitioning to POC was the dominant process determining the fate of hydrophobic OCPs in the NAB08. 3) Sediments and benthic biota were collected along the Palmer Long Term Ecological Research grids. For the first time, POPs concentrations in the Western Antarctic Peninsula (WAP) continental shelf sediments, porewater, and benthic deposit feeding holothurians were determined. High concentrations of POPs were found in close vicinity to major scientific research stations. Concentrations decreased sharply away from the locations with anthropogenic activity. This suggested that local activities were the dominant source of POPs in the WAP rather than long range transport. The Westerlies and Antarctic Circumpolar Current may have acted as dynamical barriers to transports from continents. The majority of POPs in the WAP sediments was bound to black carbon and was not available for uptake by benthic biota. POPs in the holothurians were in equilibrium with those in porewater. Different bioaccumulation factors obtained suggested that there were differences in lipids of different benthos and in situ contamination patterns.