Diane M. McKnight R.M. Cory Mark W. Williams Robert L. Runkel Matthew P. Miller 2006 <div class="hlFld-Abstract"><div id="abstractBox"><p class="articleBody_abstractText">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<span>&nbsp;</span>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<span>&nbsp;</span>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<span>&nbsp;</span>s^-1) and production of nitrate (λ = −1.0 × 10^-³<span>&nbsp;</span>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.</p></div></div><div class="hlFld-Fulltext"><br data-mce-bogus="1"></div> application/pdf 10.1021/es060635j en ACS Publications Hyporheic exchange and fulvic acid redox reactions in an alpine stream/wetland ecosystem, Colorado front range article