Diel variation in element concentrations, Peru Creek, Summit County, Colorado

Two diel samplings, in early July and mid-August, and one along-stream sampling, in late July, were completed at Peru Creek, a mountain stream affected by acid mine drainage. Three different processes were found to control diel cycling of element concentrations. The concentrations of SO42-, Mn, Zn, Si, Mg, K and Ca were primarily controlled by hydrology, particularly melting of snow. Diel Fe cycles were produced by photochemical reduction of Fe(III) species and reoxidation during the night. Nitrate cycling was controlled by its uptake by instream vegetation during daylight hours. (C) 1998 Elsevier Science B.V. All rights reserved.