Fine-particle sediment is the ultimate repository for many persistent contaminants in the environment. In aquatic systems where sediments accumulate year-after-year, we can often retrieve a core that contains a record of contaminant accumulation spanning several decades.
Interpretation of even the most ideal core is often complicated by delayed delivery of material from the drainage basin and by post-depositional mixing. Both processes can alter the perceived timing of depositional events preserved in the core. For example, gradual erosion of material from the soils of the surrounding drainage basin may cause a contaminant to accumulate in the core long after atmospheric delivery ceases. Mechanical or biological processes may mix contaminated sediment into deeper, uncontaminated layers of the core, also complicating historical interpretation.
As part of my work, I have developed simple numerical models of drainage basin holdup and post-depositional mixing that can be applied to the interpretation of sediment cores — in particular, to the interpretation of atmospheric contaminant delivery flux. These models have been applied to our best-dated cores from many environments in the Hudson Basin, including urban and rural lakes and marshes, and have been tested against known records of contaminant delivery. My collaborators and I are currently using these models to examine the history of contaminant delivery and human exposure in urban environments including the New York metropolitan area, and in sensitive rural environments downwind of industrial areas and coal-fired power plants.