Vertical profiles of pore water and sediment solids chemistry were obtained from two sites in Lake Erie. Samples were collected using both gravity coring and pore water 'peeper' techniques. In general, concentrations of nutrients and toxic metals in sediment solids decreased with increasing depth. Comparison of pore water 'peeper' data to gravity core data showed that 'peeper' data provides higher resolution near the sediment-water interface. The thermodynamic tendency of metal phosphate and carbonate mineral phases to precipitate in Lake Erie sediments has been calculated by means of an ion-pair model of the interstitial water chemistry.

"PB82247602." "EPA 600/3-81-046." "July 1981." "Contract no. R805716020." "Project officer David Dolan." Includes bibliographical references (p. 138-146). Photocopy.

Vertical profiles of pore water and sediment solids chemistry were obtained from two sites in Lake Erie. Samples were collected using both gravity coring and pore water ""peeper" techniques. In general, concentrations of nutrients and toxic metals in sediment solids decreased with increasing depth. Comparison of pore water "peeper" data to gravity core data showed that "peeper" data provides higher resolution near the sediment-water interface. The thermodynamic tendency of metal phosphate and carbonate mineral phases to precipitate in Lake Erie sediments has been calculated by means of an ion-pair model of the interstitial water chemistry. The calculations suggest that detrital calcite, argonite, and dolomite should be dissolving in the sediments, but that iron and manganese carbonates should be precipitating. Regenerated phosphate should be reacting with calcium, iron, manganese, and lead to form authigenic mineral phases. Whitlockite (Cab3s(POb4s)b2s) and not hydroxylapatite (Cab5s(POb4s)b3sOH) is the predicted mieral phase controlling phosphate solubility. Rates of anaerobic decomposition of Lake Erie sediments from one locality were determined for seven depth intervals at three temperatures. Concentration increases of bicarbonate, phosphate, ammonium, calcium, magnesium, iron, and maganese in pore water withinin any given depth interval followed zeroth order kinetics and exhibited Arrhenius temperature dependency. The observed release rates decrease exponentially with the depth in the sediment due to a corresponding decrease in the amount of oxidizable organic matter and acid hydrolyzable mineral phases.