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We have evaluated a number of laboratory tests of dispersant effectiveness using commercial oil spill products and No. 2 and No. 6 fuel oils. The tests-the EPA, Mackay/Steelman, Russian, French, Warren Spring, and an interfacial tension method developed at SRI-are reviewed in terms of type, scale, method of applying mixing energy, and the time required to conduct a product evaluation. The experimental results, compared in terms of the precision of the test data and the effectiveness ranking order of the six nonionic dispersants, demonstrate that the relative effectiveness found for the dispersants varies appreciably as a function of the testing method. Reasons for the variations are discussed and recommendations are presented on how to achieve dispersant testing data that are more representative of real-world conditions. Of the six testing methods evaluated, the EPA, Mackay/Steelman, and the interfacial tension methods are the most amenable to improvement.

A procedure for evaluating the effectiveness of oil-dispersing chemicals has been developed. Using the apparatus originally designed for the Navy specification for solvent-emulsifiers, test conditions were adapted to correspond more closely to typical environmental conditions. Test conditions having the greatest effect on dispersant performance included: type of oil, composition of salt water solution, degree of agitation of chemical/oil mixture, and the degree of contact between chemical and oil prior to agitation. Results from this modified procedure, the Simulated Environmental Tank (SET) Test, correspond well with results from simple field tests. Field tests have limited precision and reproducibility. This lack of a reliable index of field performance with which to compare laboratory results hinders refinement of standard test procedures. The SET Test, which produces results corresponding favorably with field performance, to the extent field performance can be determined, and which simulates typical environmental conditions, is proposed as a meaningful interim solution to this problem of dispersant evaluation.

The purpose of this investigation was to obtain data on aDd study the faetors a1fectlng the saUnlty of the Delaware River from Philadelphia, Pa., tothe Appoqu1n1m1nk River, Del. The general cheJPlca1 quality of water in the estuary is described, including changes in salinity in the river C!I'OSIJ sectioJl ami proftle, dIUrnal and seasonal changes, and the e1fects of rainfall, sea level. and winds on saUnity. Relationships are estabUshed of the concentrations of chloride and dissolved soUds to specific conductance. In addition to chloride profiles and isochlor plots, time series are plotted for salinIty or some quantity representing salinity, freshwater discharge, mean river level, aDd mean sealevel. The two major variables which appear to have the greatest e1fect on the saUnlty of the estuary are the freshwater flow of the river and sea level. The most favorable combination of these variables for saltwater encroacbment occurs from August to early October and the least favorable combination occurs between December and May. Bl 1'19118. t.-Locatlon of Illlmpllng stations between PhDade1phla, Pa., and Appoqulnbnlnk River, Del. (Bakel'll Range).

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