Reports
Interstitial water chemistry of Chesapeake Bay sediments
1977, Bricker, O.P., Matisoff, G., and Holdren, G.R., Jr.
Basic Data Report 9
Abstract
The environment within the first hundred centimeters beneath the sediment-water interface in estuarine systems undergoes large scale chemical changes. Significant geochemical reactions occur between trapped interstitial waters and sediment particles in response to reducing conditions induced by biologically mediated oxidation of organic matter. Terrigeneous detrital material, stable in the oxidizing conditions of the subaerial weathering zone, is eroded and transported to the estuary via rivers and shoreline processes. Upon deposition and burial this material is exposed to anoxic conditions under which many of the detrital components are unstable and highly reactive.
As a result of the reactions that occur in the anoxic environment, the composition of the interstitial waters differs drastically from that of the overlying water column and a new assemblage of minerals, stable in anoxic conditions, is formed. Because of concentration differences between the interstitial fluids and the water column, steep concentration gradients develop in the upper zone of the sediment. The dissolved species in the more highly concentrated interstitial waters (e.g., nutrients, trace metals) tend to be transported across the sediment-water interface into the water column. Conversely, a reverse gradient exists for sulphate which is utilized in the sediments as an oxidant by sulphate reducing bacteria. The upper zone of the sediment is thus in active communication with the overlying water and may play an important role in mediating the chemistry of the estuary.
Little work has been done on the geochemistry of estuarine sediments and even less on their interstitial fluids. In 1971, we began a program to systematically investigate the sediment-interstitial water system of the Chesapeake Bay and the role that the sediment reservoir plays in the chemistry of this estuary. The program was begun by the senior author while he was associated with the Chesapeake Bay Institute. Funding was provided by the United States Atomic Energy Commission from 1971-1975 (AT(ll-1)-3 292). In 1975, the program became a part of the Maryland Geological Survey Chesapeake Bay Earth Science Study. The data tabulated here were collected by the senior author and his graduate students. It represents the most complete and well documented set of data on estuarine interstitial water chemistry that we are aware of at this time. Various aspects of these data have been treated by Bray, 1973; Bray, et al., 1973; Troup, 1974; Troup, et al., 1974; Bricker and Troup, 1975; Troup and Bricker, 1975; Holdren, et al., 1975; Matisoff, et al., 1975; Holdren, 1977; Holdren and Bricker, 1977; Matisoff, 1977; and Goldberg, et al., 1977.
We publish the full set of data here because other investigators may find it a useful steppingstone towards an understanding of the chemistry of the estuarine environment.
