Chemical Exchanges Between Sediments and Water in the Great Lakes‐speculations on Probable Regulatory Mechanisms1

Abstract

As long as the oxygen concentration at the sediment surface does not fall below 1 or 2 mg/liter, typical deep‐water sediments in the Great Lakes will probably be found to exert a measurable but quantitatively unimportant influence on the chemistry of the overlying waters. This conclusion is supported by the case of Windermere. The sequence of more conspicuous changes that take place when the oxygen does fall below 1 mg/liter at the interface is illustrated by the case of Esthwaite Water, representative of events in lakes where biological production or organic pollution is high, where the subthermocline volume is relatively small, or both. A progressive decline in oxygen concentration from 2 mg/liter to analytical zero at the interface was accompanied by a fall in electrode potential in the upper few millimeters of sediment, correlated with mobilization and transfer into the water first of manganese and later of iron. There is a concurrent transfer into the water of substantial quantities of phosphate, previously held in complex form, which may have important biological consequences. Other changes include liberation into the water of ammonia and silicate. Further reduction of the water‐sediment system permits microbial reduction of sulfate. A third example of sediment‐water exchange occurs during winter stratification under ice cover. In Torneträsk, in the course of 95 days of ice cover, a relatively thin layer of bottom water, initially at 1C, gained heat and bicarbonate from and lost oxygen to the sediments. The density increase, arising from the heat gain, set density currents in motion that drained this contact water into the deepest parts of topographically isolated subbasins.

Phosphorus in Interstitial Water Induced by Redox Potential in Sediment of Dianchi Lake, China

“…Einsele (1936) suggested that the adsorption of phosphorus on ferric oxides during an aerobic condition controlled the phosphorus flux through the sediment-water interface, while under anaerobic conditions, due to the reductive dissolution of these oxides, it could subsequently be released. Mortimer (1941Mortimer ( , 1971 demonstrated in his classical studies that the release of phosphorus was unimportant as long as the concentration of dissolved oxygen exceeded 2 mg L −1 in the overlying water. When concentration of dissolved oxygen was below 2 mg L −1 , the phosphorus previously bound by solid ferric (hydr)oxides would be released.…”

Morphometry and mixing regime of a tropical lake: Lake Nova (Southeastern Brazil)

“…The homogeneous water column distributes dissolved oxygen in bottom waters, thus preventing diffusion of nutrients to bottom waters owing to oxidizing surface sediments porewater (Mortimer 1971, Conley et al 2009). …”

Environmental Impacts—Marine Biogeochemistry

“…In the sediment pore water, PO 4 diffuses upwards into the oxic sediment layer and can be bound to Fe-oxyhydroxides at the surface (Mortimer 1971;Krom and Berner 1981). Fe-bound P is abundant in surface sediments overlain by oxic bottom waters in the Baltic Sea (Balzer 1986;Jensen and Thamdrup 1993;Lukkari et al 2009;Mort et al 2010).…”

“…In organic-rich sediments common in the Baltic Sea, O 2 consumption by mineralisation of organic matter can create reduced conditions, if the O 2 is not replenished. When Fe-oxyhydroxides are not able to form, or they form only a thin layer on the sediment surface, PO 4 is not efficiently retained (Mortimer 1971). Furthermore, in brackish and marine environments, sulphide can restrict participation of Fe in PO 4 binding by precipitating ferrosulphides (Berner 1970;Caraco et al 1989).…”