Nutrient cycling and productivity of dystrophic lake-bog systems (Part A). Technical progress report, December 1, 1972--September 30, 1975

A sampler and an analytical and characterization scheme were developed to investigate the chemical and physical state of iron in a highly stained acid bog lake. Iron fractions were chemically separated by reactivity to bathophenanthroline (BPN) after specific digestion procedures. Physical separation involved anaerobic in situ filtration (450 nm), and in situ dialysis (4.8 nm). This resulted in three size classes: particulate, colloidal, and dissolved. Unlike pH 6-8 lakes, inorganic, nonreactive species of iron [e.g., Fe(OH)$sub 3$] represent minor amounts of the total iron in North Gate Lake. In situ radiochemical analyses revealed that colloidal sized reactive ferric iron predominates in the oxygenated epilimnion, while dialyzable or dissolved ferrous iron increases with depth. Unlike iron, organic matter is present in a nontransient colloidal state. In acid (pH 4-5) bog lakes ferric iron is not colloidal as an inorganic complex (OH$sup -$), but colloidal as reactive Fe$sup +$$sub 3$ by complexation with the colloidal organic acids. After thermally induced mixing with anaerobic waters, ferric iron is reduced and dissolved. However, some of the BPN reactive iron remains colloidal suggesting the presence of a residual ferrous organic complex. (auth