The Carbon-Oxygen Distribution In New York Bight

O'Connor, Donald J.
Mancini, John L.
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The steady-state analysis presented in this report provides a basis for assessment of dissolved oxygen in the New York Bight, particularly in the apex area. The analysis indicates that the discharge of carbonaceous and nitrogenous wastes does not materially affect the dissolved oxygen levels through bacterial oxidation. Furthermore, the discharge of solids (sludge disposal, dredge spoils and construction debrisj do not influence these concentrations on a bight-wide scale. The localized sludge disposal area is evidently affected in this regard, but this area is restricted to a relatively limited extent. On the other hand, the depression of dissolved oxygen, particularly in the hypolimetic waters, is affected by phytoplankton respiration and decay and the vertical transport structure. It is probable that the discharge of wastewater from the treatment plants and urban runoff has some effect on the growth of phytoplankton and the subsequent decay tbrough the inorganic nutrient route. The degree to which water quality conditions are affected by these inputs may be quantified by the development and validation of a model defining these kinetic interactions. The analysis, developed in this second phase, will be extended to incorporate the kinetic routes, relating the growth and decay of the phytoplankton to the nutrient concentrations resulting from these wastewater inputs. Thus, the effect; of the discharges will be defined, providing a basis for areawide water quality planning, particularly with respect to the relative influence of the point sources from treatment plants and the distributed sources from urban runoff by contrast to the effects of other inputs such as the disposal practices and atmospheric inputs. The present analysis is directed to the definition of a transport structure in accordance with the original contract to provide the Brookhaven investigators with a reasonable transport field for summer conditions. The transport equations included advective and dispersive terms in a multi--segmented horizontal system with two vertical layers. The advective terms were developed by a minimum energy principle, which yield the general observed flow pattern in the Bight. The overall transport field also included consistent values of the various disperation coefficinents. It is recognized that advective-dispersive models of this nature do not necessarily result in a unique solution for the transport. However, its validity to represent average summer conditions is demonstrated by its ability to reproduce the salinity distribution for the two years. The analysis further indicates that the dissolved oxygen concentration in the hypolimnetic waters is particularly sensitive to the respiration and decay rates of the phytoplankton and the vertical dispersion coefficients. Relatively small changes of these paremeters, within the range of measured values, cases significant changes in the dissolved oxygen levels. Thus, from both a transport and kinetic viewpoint, the present analysis reasonably reproduces observed water quality conditions and permits assussment of the effect of wastewater inputs. In view of the potential significance of these aischarges on dissolved oxygen and other water quality parameters this analysis had indicated the analytic direction on which to proceed and provide a valid basis for the more definitive time variable analysis.
Carbon-Oxygen Distribution , New York Bight