DEVELOPMENT OF ORGANIC CARBON AND PCB LOADINGS FROM MULTIPLE SOURCE CATEGORIES TO THE DELAWARE RIVER ESTUARY

External mass loads of organic carbon and penta-PCB were required for development of the PCB TMDL model for the Delaware River Estuary. Daily organic carbon and penta-PCB loads were developed to perform the short-term calibration simulations for a continuous 19-month period (September 1, 2001 through March 31, 2003). A one year daily loading time series was subset and cycled to allow longer simulation periods. Daily loads of particulate detrital carbon (PDC) and biotic carbon (BIC) were estimated for the principal source categories that included marshes, tributaries, the non-tidal Delaware River, point discharges, wet and dry atmospheric deposition, combined sewer overflows (CSOs), and non-point sources. The load distribution suggests that while the majority of the carbon in the system is derived from primary production in the bay in the form of BIC, marsh derived PDC is the dominant form of carbon in the tidal river. External daily loads of penta-PCBs were estimated for principal source categories that included contaminated sites, non-point sources, point discharges, tributaries, the non-tidal Delaware River, wet and dry atmospheric deposition, and CSOs.Summation of daily loads allowed direct comparison of the relative magnitudes of the different source categories. Contaminated sites contributed approximately 32% of the 19-month penta- PCB external load and non-point sources contributed approximately 19%. By contrast, point discharges contributed approximately 13% of the penta-PCB external load. Loading uncertainties were estimated using a Monte Carlo analysis for each PCB source category. This analysis allowed estimation of the uncertainty for each source category, comparisons of uncertainty among categories, and identification of reasonable upper and lower limits for loadings for each category and for the overall penta-PCB load.