Date of Award
Master of Science in Civil and Environmental Engineering
Civil and Environmental Engineering
Calvin P.C. Poon
A knowledge of nutrient concentration levels in the sediments, using nutrient profile as an indicator of pollution, can be a revealing and important factor in defining the water quality of the Bay. The intent of this study was to examine the nutrient distribution of nitrogen and phosphoru3 in sediment cores of Narragansett Bay. The findings would serve to indicate the effect of man's activities on the r-ate of estuarine eutrophication and to interpret the pollution history of the Bay.
Results obtained-indicate that the sediments have a greater probability of concentrating pollutants and therefore, are better used to indicate some types of bay pollution than analyses of the overlying water. It was found in the analyses of core sections in each station that total nitrogen and total phosphorus increase rapidly in the upper 4-inch section. From this result we postulate that the Bay water was fertilized by man during the past two centuries. The available nitrogen and phosphorous concentration levels increase with greater depth. Consequently, we can expect the sediment dredging to such depth will make the newly exposed sediment nutrients more available for algae• growth. Therefore, on the basis of available nitrogen and phosphorus, sediment dredging gives no beneficial but ill effect on the Bay water. The best way to protect the water quality of the Bay i3 to reduce the rate of nutrient input, especially phosphorus, to the estuary.
With the relative amount of nutrient in the sediment of stations sampled, we can divide the Bay into three environments: polluted district--including Stations Y, Y.Y., and Z; lightly polluted district--including Stations Land H; nonpolluted district--including Stations G and B.
The presence and amounts of chemical substances such as organic carbon, iron and manganese, especially iron, associate with the nutrient deposition well, and thus can be correlated in the interpretation of the deposition mechanisms. The ratio of N:P was low compared with other reports. It showed that the eutrophication potential of the Bay is likely dependent on nitrogen. However, since some blue-green algae can fix the nitrogen gas from the atmosphere from which it is not easy to control, a reduction in the rate of P input to minimize the phosphorus contribution to the estuary in order to control the algal nuisances is necessary for recreational use and increasing shoreline real estate value.
Sheih, Mung-Shium Jack, "Nutrients in Narragansett Bay Sediments" (1974). Open Access Master's Theses. Paper 2115.