HEAVY METAL CONCENTRATIONS IN LACUSTRINE SEDIMENTS OF DEVELOPED AND UNDEVELOPED WATERSHEDS, WILLIAMSBURG, VA

Increasing population density in many areas of southeastern Virginia forces change in land use for many watersheds.  The Lake Matoaka and Jolly Pond drainage basins are approximately the same size (~600 ha) and <10 km apart but differ significantly in development.  Lake Matoaka was created through damming projects between 1720 and 1730.  The Matoaka basin is more urbanized (63% forested, 12% low population density residential and 22% high population residential or commercial) and includes the academic and housing complexes and surrounding businesses of the College of William & Mary.  Jolly Pond and the two dams that created it first appear on maps dating back to 1860.  The Jolly Pond basin is relatively undisturbed and largely forested, zoned as a general agricultural district with only small scattered parcels of low-density residential land. 

Because of their persistence as an aquatic pollutant, heavy metal concentrations were measured in order to determine the impact of anthropogenic activities and the relative health of the basins.  Cores were extracted from Lake Matoaka and Jolly Pond using a Russian peat corer, and measurements were made of extractable metals.  Lead, cadmium, and chromium concentrations were measured to depths of 1.5 meters (Matoaka) and 1.0 meter (Jolly Pond).  It was found that Lake Matoaka has relatively high lead concentrations, exceeding 300 ppm at its peak while Jolly Pond maintained lower and more consistent levels of lead, most samples containing 30-50 ppm.  Cadmium concentrations were near baseline for both sites.  Chromium concentrations were more scattered in Lake Matoaka and Jolly Pond but overall maintain concentrations near baseline.  In addition, carbon and nitrogen concentrations were determined to examine the organic matter input and sedimentation rates will be determined by ¹³⁷Cs dating.  Our data indicate that more urbanized drainage basins contain significantly higher concentrations of heavy metals.

Man-made mill ponds in southeast VA provide a unique historical record of the human impact on small watersheds.  The studied ponds are in the James River basin and eventually flow into the Chesapeake Bay.  Taken together, our data demonstrate the significant impact that development and other anthropogenic activity can have on small watersheds.