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 (α ≈ 10-3 s-1). Parallel factor analysis of fluorescence spectra was used to quantify the redox state of dissolved fulvic acids. The rate coefficient for oxidation of reduced fulvic acids (λ = 6.5 × 10-3 s-1) in the stream indicates that electron-transfer reactions occur over short time scales. The rate coefficients for decay of ammonium (λ = 1.2 × 10-3 s-1) and production of nitrate (λ = −1.0 × 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.
|Title||Hyporheic exchange and fulvic acid redox reactions in an alpine stream/wetland ecosystem, Colorado front range|
|Authors||Matthew P. Miller, Diane M. McKnight, R.M. Cory, Mark W. Williams, Robert L. Runkel|
|Publication Subtype||Journal Article|
|Series Title||Environmental Science & Technology|
|Record Source||USGS Publications Warehouse|
|USGS Organization||Colorado Water Science Center; Toxic Substances Hydrology Program|