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Sediment from the lower Cuyahoga River (5.8 river km from the mouth at Lake Erie) was dispersed in reactors containing simulated lake water constituted to have pH, dissolved oxygen (DO), alkalinity, and hardness values typical of Great Lakes Waters. The parameters of pH and DO were maintained constant during the course of the experiments, while calcium and sediment dispersion concentrations were systematically varied. The calcium ranged from 5 to 120 mg/litre and the sediment from 0.5 to 50 g(dry)/litre.
The materials investigated for release from the sediment dispersions included magnesium, cadmium, copper, lead, zinc, iron, manganese, chromium, arsenic, total dissolved phosphate as PO4, and total Kjeldahl nitrogen. In general, the extent of release was inversely related to the calcium and sediment concentrations. Significantly, the unit release of metals and nutrients in oxygenated waters increased two to five-fold with each order-of-magnitude decrease in sediment dispersion concentration.
The methods of the research bear upon the development of procedures for evaluating the potential impact of dredging operations on water quality. The results of this investigation show that the amounts of dredge spoil constituents released into solution can be comparable in magnitude to those of dissolved mineral species in rivers and outfalls.
dredging, dredge spoil, suspended sediments, water pollution, sediment-water interfaces, metals, nutrients, phosphates, calcium hardness, water pollution sources, aquatic toxicology
Physical scientist, U.S. Army Engineer District, Environmental Resources Branch, Detroit, Mich.
Professor of environmental and water resources engineering and chairman of the University Program in Water Resources, University of Michigan, Ann Arbor, Mich.
Environmental chemist, U.S. Environmental Protection Agency, Enforcement Division, Region V, Chicago, Ill.
Research chemist, National Institute of Occupational Safety and Health, Division of Physical Sciences and Engineering, Physical Measurements Branch, Cincinnati, Ohio