GEOCHEMISTRY OF RECENT (<100 Y) SEDIMENTS IN THE CORSICA RIVER

The Corsica River, located on the eastern shore of Maryland, has been targeted for restoration to help reduce the sediment and nutrient load that ultimately reaches Chesapeake Bay. Previous work has indicated that the primary source of these materials to the Corsica is from agricultural land use. However, their fate and the potential of the riverbed as a secondary source is largely unknown. This study provides preliminary data concerning the geochemical characteristics of recent sediments in the Corsica River to examine the past (~100-y) history of sediment and nutrient burial, so that future changes related to the restoration efforts can be better understood.

Riverbed sediments were collected in June 2006 using a piston corer and analyzed for their chemical and textural properties. 100-y sedimentation rates have been determined using the naturally occurring radioisotope ²¹⁰Pb (half-life 22.3 y) and verified with ¹³⁷Cs (half-life 30.7) geochronology. This provides a basis for interpreting down-core profiles of grain size and phosphorus, nitrogen, and heavy metal (e.g., Zn, Cu, Pb) concentrations. In conjunction with measurements of sediment-water exchange of oxygen, nitrogen and phosphorus, the relative role of N and P burial versus recycling can be evaluated. These data suggest that unlike many shallow water estuarine sedimentary environments, phosphorus release into the water column is a major term in the estuarine phosphorus budget. Conversion of iron oxide minerals into iron sulfide minerals in these brackish, oxygen-stressed environments results in P remobilization.