THE ROLE OF THE FLOODPLAIN IN THE STORAGE OF CONTAMINANTS ALONG MEANDERING RIVERS

The Housatonic river drains a 1950 square mile area, meandering through Western Massachusetts and Connecticut before outletting into the Long Island Sound. Between 1932 and 1977, General Electric dumped polychlorinated biphenyls into the headwaters of the Housatonic, causing the toxic and carcinogenic substance to spread downstream into both the floodplain and the riparian ecosystem. Since the 1980s, GE, the USGS, and the EPA have collected over 9,600 sediment samples from the river and its floodplain, testing for PCB concentrations at various depths. Although this comprehensive dataset has been publicly available since 2003, there has yet been no investigation into how spatial variability in PCB concentrations might reflect the fluvial geomorphology of the floodplain. In this project, we will combine the preexisting data with our own supplementary sediment cores to explore such patterns across the floodplain. We will use the physical properties of PCBs -- e.g. their preferential adsorption to fine grained material -- to answer questions about how sediment is distributed and reworked within the floodplain. Those questions include what role floodplain depressions such as oxbow lakes play in sequestering sediment-adsorbed legacy contaminants, and whether grain-size heterogeneity within point bars reflected by PCB distributions. We will also calculate an approximate sediment budget for the river and examine the implications that budget has on the fate of currently stored contaminants.