This interdisciplinary study is examining the relative importance of
biological, physical and chemical processes in controlling the fluxes of
particles, fluids and contaminants across the sediment-water interface.
The geology portion of the study has focused on two areas: biologically
dominated lower Chesapeake Bay and physically dominated York River subestuary.
Sediment cores collected for sedimentological and geochronological studies
from the two areas reveal dramatic differences in seabed mixing regimes.
The upper half meter of the seabed at the lower bay sites is intensively
reworked by benthic infauna and no physical sedimentary structures are
preserved at depth. For the York River site, deep physical mixing dominates
particle dynamics, with erosion/deposition of as much as 1.5 meters of
seabed over time scales of a few years or less. In both areas, deep mixing
and low accumulation rates indicate particle residence times on the order
of a century. Therefore, particle reactive contaminants in these areas
are cycled in the upper portion of the seabed for similarly long periods
before being removed by permanent burial.
Future efforts will focus on the nature of physical mixing and distribution
of sedimentary environments in the York River subestuary. Work is currently
underway to determine the timing and physical forcing mechanisms for the
dramatic mixing depths observed. This work has important implications for
our understanding of contaminant cycling in estuaries, and is providing
basic knowledge for our understanding of the geological evolution of estuarine
systems.
FUNDING AGENCY: Office
of Naval Research, Harbor Processes Program
STUDENTS: Timothy Dellapenna
P.I.'s: