PROPERTIES AND REACTIVITY OF DISSOLVED ORGANIC MATTER FROM PRAIRIE POTHOLE WETLANDS

Dissolved organic matter (DOM) plays critical roles in the carbon cycle, ecosystem function, the biogeochemistry of major and minor elements, and the attenuation of synthetic organic contaminants. DOM from diverse environments is formed from both higher plant and single-cell organism precursor materials, but do not resemble the biogenic substances from which they are derived. In particular labile components such as organic nitrogen and sulfur compounds (e.g., proteins, phytochelatins, and amino acids) are rapidly utilized by heterotrophic organisms, and the remaining material “reworked” to form molecules depleted in nitrogen and sulfur. Unlike other aquatic systems DOM derived from Prairie Pothole wetlands (PPW), however, are highly enriched in organic nitrogen and sulfur that are formed from secondary abiotic reactions, producing organic matter that does not resemble their biogenic precursors. Evidence based upon high-resolution mass spectrometry analysis demonstrate that the nitrogen and sulfur functional groups present in PPW DOM impart reactivity that make this pool of organic matter unique relative to dissolved organic matter derived from other aquatic environments. For example voltammetric analysis of PPW DOM reveals electron accepting and donating capacities (EAC/EDC respectively) for these substances that are unique to this system and not observed for organic matter isolated from other lacustrine and riverine environments. Further, EAC and EDC influences DOM sorption to iron oxides whereby the reduced form had significantly lower adsorption capacities relative to the fully oxidized state. This change in adsorption capacity was not observed for the aquatic reference DOM, Suwannee River fulvic acid, and is attributed to changes in the redox state of the sulfur moieties associated with PPW DOM.