The influence of colloidal organic matter on iron and iron-phosphorus cycling in an acid bog lake1

TLDR: The relationship between iron and phosphorus and the relationship of these elements to colloidal organic matter (COM) was studied in a meromictic acid bog lake by chemical characterization, filtration and in situ dialysis, with in situ experiments with labeled components.

Abstract: The relationship between iron and phosphorus and the relationship of these elements to colloidal organic matter (COM ) was studied in a meromictic acid bog lake by chemical characterization, filtration and in situ dialysis, and in situ experiments with labeled components. Bathophenanthroline ( BPN ) rcactivc ferrous iron existed in true solution ( dialyzable ) in constantly anaerobic monimolimnetic water; iron was of colloidal size. in the aerobic epilimnion reactive ferric Intermediate depths, oxygenated only during spring, contained two forms of ferrous iron reactive to BPN: dialyzable ferrous iron (Fe’+) and colloidal Fe( II ) which may have originated through in situ reduction of colloidal reactive ferric iron and may be present as a COM-Fe”’ complex. The amount of COM influenced the fate of dialyzable Fe” (92% of total iron) and dialyzable POC-P (85% of total phosphorus) present in anaerobic strata before aeration. Aeration with soluble organic matter present (COM absent) resulted in the formation of colloidal nonreactive ferric iron (84% of total iron) and %0/o colloidal PO.I-P, while aeration with 20 mg liter-’ COM resulted in only 36% colloidal, nonreactive ferric iron and 19% colloidal PO.i-P. COM apparently masks the cationic propertics of colloidal ferric iron and retards the formation of nonreactive Fc( III), allowing most of the Pot-P to remain free in solution and biologically available.