THE TEMPORAL AND SPATIAL DISTRIBUTION OF TRACE METALS IN THE FLUVIAL AND LACUSTRINE SEDIMENTS OF THE SOUTHERN CHESAPEAKE BAY BASIN

The progressively declining ecological condition of the Chesapeake Bay is attributed to the influx of contaminants associated with sediment loads supplied by its largest tributaries. Reconciling historic mining and agriculture with current urban expansion can illustrate the evolution of metal loading by point and non-point sources in a dynamic landscape. These efforts permit the preservation of ecosystems that impart biological and economic value to this estuarine system. This study analyzes the spatial distributions of Al, Ca, Mg, Cr, Cd, As, Se, Pb, Cu, Zn, Mn, and Fe in the surficial sediments of the waterways of the Virginia portion of the Chesapeake Bay basin. The historic fluctuations in trace metal input were determined with sediment cores obtained in fluvial-estuarine environments and reservoirs in the upper reaches of the basin. The sediment cores underwent radiochronological analyses (²¹⁰Pb and ¹³⁷Cs) and the metal profiles revealed high basal enrichment factors (EF) between 0.05 and 40.24, which are interpreted to represent early nineteenth century agricultural activity and primary resource extraction. Surficial enrichment factors ranged between 0.01(Cu) and 1420.81 (Cd). Elevated enrichments of Pb, Cu, Zn, and Cd are a possible consequence of urban expansion and industrial development along major transportation corridors. Contemporary surficial enrichments of As, Se, and Cr ranged between 0 and 137.45, and are affected by lithological and atmospheric sources. Pearson correlations suggest mining and agricultural legacy, coupled with aerosol deposition, is responsible for high metal concentrations in western lakes and headwater reaches of fluvial systems, while metal accumulation in estuarine reaches of rivers can be attributed to urban effluence and the remobilization of legacy sediments.