The influence of hyporheic zone interactions on the redoxstate of fulvic acids
and other redox active specieswas investigated in an alpine stream
and adjacent wetl
and,which is a more reducing environment. A tracer injectionexperiment using bromide (Br
-) was conducted in thestream system. Simulations with a transport model showedthat rates of exchange between the stream
and hyporheiczone were rapid (
![](/images/entities/ap.gif)
10
-3 s
-1). Parallel factor analysisof fluorescence spectra was used to quantify the redox stateof dissolved fulvic acids. The rate coefficient for oxidationof reduced fulvic acids (
![](/images/gifchars/lambda.gif)
= 6.5 × 10
-3 s
-1) in thestream indicates that electron-transfer reactions occurover short time scales. The rate coefficients for decay ofammonium (
![](/images/gifchars/lambda.gif)
= 1.2 × 10
-3 s
-1)
and production ofnitrate (
![](/images/gifchars/lambda.gif)
= -1.0 × 10
-3 s
-1) were opposite in sign butalmost equal in magnitude. Our results suggest that fulvicacids are involved in rapid electron-transfer processesin
and near the stream channel
and may be important indetermining ecological energy flow at the catchment scale.