The influence of ‘oxidizing and reducing conditions upon the distribution of some clcments in lake sediments

surface muds, reduced subsurface muds, and glacial clays collected in Windermere and Esthwaite Water in the English Lake District. The relatively organic lake muds exhibit the highest concentrations of C, S, Cu, Sn, and Ni. Many of the oxidate crusts exhibit strong enrichment in Mn, Fe, Ba, Sr, Pb, and Zn. Ti, Li, Rb, Co, P, and MO are also enriched in some crusts. S, Sn, and Ni reach their highest levels in the reducing subsurface muds, but Mn, and to a lesser extent Fe and MO, are higher in the oxidized than in the reduced muds. Relations between the elements in the various sediments are examined, and the English oxidate crusts are compared with lake and stream ores in Sweden and Finland, and with marine manganese nodules. These marine nodules are frequently enriched in Cu, Ni, Co, MO, V, Ag, and Sn to a far higher degree than the freshwater ferromanganese concretions. Some freshwater crusts exhibit enrichments in Pb, Zn, and Ba of the same order as those observed in marine manganese nodules. INTBODUCTION One of the most important factors affect-ing the exchange of dissolved substances between mud and water in lakes is the redox potential gradient in the syste