title: Hyporheic exchange and fulvic acid redox reactions in an Alpine stream/wetland ecosystem, Colorado Front Range.
abstract: The influence of hyporheic zone interactions on the redox state of fulvic acids and other redox active species was investigated in an alpine stream and adjacent wetland, which is a more reducing environment. A tracer injection experiment using bromide (Br-) was conducted in the stream system. Simulations with a transport model showed that rates of exchange between the stream and hyporheic zone were rapid (alpha approximately 10(-3) s(-1)). Parallel factor analysis of fluorescence spectra was used to quantifythe redox state of dissolved fulvic acids. The rate coefficient for oxidation of reduced fulvic acids (lambda = 6.5 x 10(-3) s(-1)) in the stream indicates that electron-transfer reactions occur over short time scales. The rate coefficients for decay of ammonium (lambda = 1.2 x 10(-3) s(-1)) and production of nitrate (lambda = -1.0 x 10(-3) s(-1)) were opposite in sign but almost equal in magnitude. Our results suggest that fulvic acids are involved in rapid electron-transfer processes in and near the stream channel and may be important in determining ecological energy flow at the catchment scale.
authors.affiliation: Department of Civil, Environmental, and Architectural Engineering, Institute of Arctic and Alpine Research, University of Colorado, Boulder 80309-0450, USA. Matthew.P.Miler-1@Colorado.edu
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Miller
authors.forename: Diane M
authors.initials: DM
authors.lastname: McKnight
authors.forename: Rose M
authors.initials: RM
authors.lastname: Cory
authors.forename: Mark W
authors.initials: MW
authors.lastname: Williams
authors.forename: Robert L
authors.initials: RL
authors.lastname: Runkel
mesh_terms: D001578:Benzopyrans / Q000737:chemistry*; D001966:Bromine / Q000032:analysis; D002244:Carbon / Q000032:analysis; D003120:Colorado; D009566:Nitrates / Q000032:analysis; D010084:Oxidation-Reduction; D000644:Quaternary Ammonium Compounds / Q000032:analysis; D045483:Rivers / Q000737:chemistry*; D053833:Wetlands
chemical_list: D001578:Benzopyrans; D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D002244:Carbon; D001966:Bromine; C005023:fulvic acid