Date of Award
Doctor of Philosophy in Oceanography
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 as well as global warming, previous polluted reservoirs such as soil, large water bodies, and glaciers may act as secondary sources returning these POPs back to the atmosphere and ocean. It was also 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 the atmosphere during phytoplankton blooms and then depositing it to the deep ocean. It has been found that POPs accumulate to high levels in apex predators such as whales and polar bears. To fully understand how POPs biomagnify along the food web, it is important to quantify the transfer of POPs from environmental media (sediments and water) to the base of food webs. This dissertation research was conducted in three remote oceans to verify these hypotheses. 1) In the first study, air and water samples were collected simultaneously on RIV Revelle during a scientific cruise 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. In contrast, this study showed gas exchange hexachlorobenzene of (HCB) was at steady-state between the air and ocean with no net transfer of HCB. 2) In the second study, air, water, and zooplankton samples (copepod Calanus) were collected simultaneously during the North Atlantic Bloom (NAB) in 2008 in a relatively small area south of Iceland. The POPs measurement showed dissolved phase concentrations of lipophilic OCP remained constant with time as the bloom evolved. Also, the OCPs were not being drawn from air to water during the main bloom as previous studies have hypothesized. Further our data and data from prior Arctic measurements suggested that the Arctic was a source of higher concentrations of hexachlorocyclohexanes (HCHs) and both the atmospheric (polar easterlies) as well as oceanic transport (East Greenland Current) would bring HCHs to the lower latitudes. Last, the measurements indicated that equilibrium partitioning governed the transfer of POPs from water into Calanus. To explore the measurements further, a box model was developed and used to investigate the fate of POPs during the bloom. Biogeochemical processes considered included air-water exchange, partitioning to particulate organic carbon (POC), removal by sinking POC, and biogeochemical degradation. Modeling results demonstrated that partitioning to POC was the dominant process determining the fate of OCPs in the NAB 2008. 3) In a final study, 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 by atmospheric and oceanic motion. The Westerlies and Antarctic Circumpolar Current may have acted as dynamical barriers to transports from the southern 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 the porewater. Different bioaccumulation factors obtained suggested that there were differences in lipids of the different benthos and in situ contamination patterns.
Zhang, Lin, "TRANSPORT AND PARTITIONING OF ORGANOCHLORINE POLLUTANTS IN THE OPEN OCEANS" (2012). Open Access Dissertations. Paper 1334.