runoff from data collected on five 

 test drainage basins in Pennsylvania, 

 Maryland and Virginia, and (6) cali- 

 brating and verifying mathematical 

 models to include nonpoint source 

 loading models, stream transport mod- 

 els and estuarine response models. 



studies will provide a baseline des- 

 cription of the estuarine system 

 against which future changes can be 

 measured. The overall goal of the 

 toxics program is to provide a sound 

 scientific foundation on which ef- 

 fective strategies can be built. 



TOXICS 



The Chesapeake Bay Toxics 

 Program has been designed to address 

 a number of problems associated with 

 the estuarine environment. Two of 

 the greatest threats to an estuary 

 are sediments and toxic materials. 

 Sediments tend to fill in estuaries 

 and toxic materials adversely impact 

 the estuarine biota. These two fact- 

 ors are studied together since the 

 majority of heavy metals, radio- 

 nuclides and organic toxic chemicals, 

 are known to adsorb to fine grain 

 particles both in the water and sedi- 

 ments. To assess the impacts of 

 these materials, the toxics program 

 is pursuing research on the pres- 

 ent distribution of sediments and 

 toxic materials to the bay, and 

 the behavior and fate of sediments 

 and toxic materials within the bay. 

 The first area of investigation will 

 provide data about what toxic chemi- 

 cals are in the system now, where 

 they are located and their form 

 (e.g., inorganic, organic, etc.). The 

 second area of investigation will 

 document the types of materials en- 

 tering the bay, the various sources 

 of these materials (natural and 

 anthropogenic) , and will provide a 

 first estimate of the rates of addi- 

 tion to the estuary. The third area 

 of investigation will delineate the 

 routes and mechanisms of transport 

 of sediments and toxic materials 

 within the estuary, the sites of ac- 

 cumulation (sedimentation), the 

 chemical behavior (mobilization and 

 cycling) and will begin to identify 

 biological impacts. Together, these 



COMPONENTS OF METHODOLOGY 



FALL LINE MONITORING 



Through an interagency agreement 

 with the EPA Chesapeake Bay Program, 

 the U.S. Geological Survey is con- 

 ducting a two-year intensive study at 

 the fall line of the major rivers 

 draining into the tidal Chesapeake 

 Bay. The Susquehanna, Potomac and 

 James monitoring sites are located 

 at Conowingo, Maryland (dam and Rt. 

 40 bridge), Washington, D.C. (Chain 

 Bridge), and at Cartersville , Vir- 

 ginia, respectively. Measurements 

 are being made for suspended sedi- 

 ment, nitrogen, phosphorus, carbon, 

 trace metals, pesticides, sulfate 

 and major ions, chlorophyll a, total 

 solids and freshwater discharge. 

 Physical parameters are measured 

 daily with nutrients and metals be- 

 ing monitored monthly (twice a month 

 for Susquehanna). In addition, high- 

 flow sampling over the hydrograph is 

 being carried out to assess the im- 

 pact from upland nonpoint source run- 

 off. The products of this study in- 

 clude estimated input loadings to 

 the bay of suspended sediment, major 

 dissolved species, selected nu- 

 trient species, and trace metals, 

 plus a seasonal characterization of 

 pesticide runoff. Levels of con- 

 fidence will be made by the United 

 States Geological Survey (USGS) for 

 the various loading curves. These 

 field-measured loadings will be in- 

 troduced into the bay-wide water 

 quality model for calibration and 



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