Determination of Trace Contaminant Loads from Two Eastern Shore Tributaries of Chesapeake Bay

WRD PROJECT #: MD145
PROJECT CHIEF: Miller, Cherie V.
BEGIN DATE: 01-October-1997
END DATE: 31-August-1999

Customers currently supporting the project:

Maryland Department of the Environment
George Mason University
U.S. Geological Survey

Problem

Two tributaries on the Eastern Shore of Chesapeake Bay were proposed for intensive study of contaminant-loading to the tidal estuary in 1997-98: the Nanticoke River and the Chesterville Branch (a small tributary near the mouth of the Chester River). In order to differentiate contaminant loadings processes and mechanisms between the basins, fluvial transport will be evaluated during baseflow and stormflow hydrologic regimes. For each river, base-flow will be measured bi-monthly for 1 year and one major storm event will be sampled discretely throughout the entire rising and falling limbs of the hydrograph. Constituents will be analyzed in both particulate and dissolved phases. Contaminant concentrations in the two streams will be compared to other physical and chemical parameters such as suspended sediment, size fractionation of particles, discharge, and major ions. This will not only provide insight into the transport mechanisms, but may also reveal relations between the variables so that future studies can use less expensive surrogate variables to estimate contaminant loads. Finally, both total and base-flow annual loads will be calculated for each tributary to determine the relative importance of sources, landscapes, lithologies, and land-use patterns of contaminant fluxes in the different basins. Better resolution of the spatial differences between the basins will provide not just the fluxes of contaminants, but also the processes responsible for net inputs to the Bay. This information will be useful to managers who may be developing future BMPs to control toxic contaminants.

Objectives

1. Quantify annual tributary loadings and basin yields of trace contaminants for two Eastern Shore streams that differ fundamentally in geomorphology, land use, and geochemistry.
2. Identify basin features (such as stream discharge, land use, lithology, and basin morphology) and processes (such as particle/water distribution and chemical weathering) which cause differences in the behavior of contaminant loadings and yields.
3. Evaluate relations between trace contaminants and potential surrogate variables such as discharge, suspended-sediment concentration, grain-size fractionation, major ions, e.g., SO42- and Cl- (also a function of stormflow), atmospheric precipitation, and air and water temp (seasonally). This information is useful in identifying underlying mechanisms involved in fluvial transport (i.e., relative magnitude of groundwater vs. overland runoff input to stream channels) and for potentially reducing analytical costs in future sampling programs, in which contaminant loads could be inferred by monitoring the surrogate variables with fewer measurements of the actual contaminants.

Approach

The following tributaries were be sampled in 1997: Nanticoke River near Bridgeville, DE (0148700); and Chesterville Branch near Crumpton, Md. (01493112). Sampling strategies will be to collect (1) six base-flow samples over FY97-98 at each of the tributaries to capture seasonal variability and (2) to intensively sample one major spring storm at each river to document the behavior of each contaminant throughout the storm event (six samples per storm event per stream). All samples were collected using ultra-clean techniques to minimize contamination. These techniques are documented with quality-assurance data and described in detail in the 1992 Fall Line Toxics Final Report (see reference below). Sample-collection techniques, already worked out from the 1994 study, are different for each river, because the hydrology and modes of transport vary within each system. The sampling strategy for each river will be based on physical constraints, such as access to the river and on the results of the 1994 Tributary Synoptic, which has determined cross-sectional and seasonal variability at each site.

Related Publications

• Zynjuk, L.D., Feit, B.L., and Miller, C.V., Cheasapeake Bay Fall Line Toxics Monitoring Program, 1992, Final Report, U.S. Environmental Protection Agency for the Chesapeake Bay Program, C.P./TRS 121/94, Final Report, 175 p.