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In sediment source investigations of harbor estuaries, it is essential that the bulk composition of the shoal be determined precisely in order to relate the quantity of sediment by means of diagnostic constituents to the respective watershed source areas, effluents from industry and sewage, and contribution from the sea by tidal currents. Crystalline materials are readily identified by petrographic or x-ray diffraction techniques, but identification of organic and amorphous materials m ay require a combination of several methods.

The organic materials in fine-grained Delaware estuary bottom sediment were determined by a combination of the electron microscope, mass spectrometer, chemical techniques, and thermal methods. Amorphous diatoms were identified by scanning electron micrographs, and were quantitatively determined by differential caustic leach methods. Amorphous hydrous iron compounds were determined by the sodium dithionite method. An especially effective combination of techniques to evaluate the pyrite, organic matter, and anthracite coal in the sediment was the use of differential thermal analysis, thermogravimetric analysis, and the mass spectrometer.

The anthracite coal occurred in negligible amounts north of the confluence of the Schuylkill and Delaware Rivers and displayed progressive dispersal southward in the estuary. The coal had essentially a “point” source in the Schuylkill River watershed that drains the anthracite coal fields of Pennsylvania. The greater amount of organic matter found in the vicinity of larger cities was attributed largely to sewage. Amorphous opaline diatoms were generally best represented in the more organic-rich sediment. Amorphous iron compounds appeared more abundant in the sediment in proximity to acid effluent discharge from industry.

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