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WATER RESOURCES RESEARCH, VOL. 40, W01201, doi:10.1029/2003WR002130, 2004

Conservative and reactive solute transport in constructed wetlands

Steffanie H. Keefe

U.S. Geological Survey, Boulder, Colorado, USA


Larry B. Barber

U.S. Geological Survey, Boulder, Colorado, USA


Robert L. Runkel

U.S. Geological Survey, Denver, Colorado, USA


Joseph N. Ryan

Department of Civil and Environmental Engineering, University of Colorado, Boulder, Boulder, Colorado, USA


Diane M. McKnight

Department of Civil and Environmental Engineering, University of Colorado, Boulder, Boulder, Colorado, USA


Roland D. Wass

Water Services Department, Phoenix, Arizona, USA


Abstract

The transport of bromide, a conservative tracer, and rhodamine WT (RWT), a photodegrading tracer, was evaluated in three wastewater-dependent wetlands near Phoenix, Arizona, using a solute transport model with transient storage. Coupled sodium bromide and RWT tracer tests were performed to establish conservative transport and reactive parameters in constructed wetlands with water losses ranging from (1) relatively impermeable (15%), (2) moderately leaky (45%), and (3) significantly leaky (76%). RWT first-order photolysis rates and sorption coefficients were determined from independent field and laboratory experiments. Individual wetland hydraulic profiles influenced the extent of transient storage interaction in stagnant water areas and consequently RWT removal. Solute mixing and transient storage interaction occurred in the impermeable wetland, resulting in 21% RWT mass loss from main channel and storage zone photolysis (10%) and sorption (11%) reactions. Advection and dispersion governed solute transport in the leaky wetland, limiting RWT photolysis removal (1.2%) and favoring main channel sorption (3.6%). The moderately leaky wetland contained islands parallel to flow, producing channel flow and minimizing RWT losses (1.6%).

Received 7 March 2003; accepted 17 October 2003; published 27 January 2004.

Index Terms: 1890 Hydrology: Wetlands; 1871 Hydrology: Surface water quality; 3230 Mathematical Geophysics: Numerical solutions.

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Citation: Keefe, S. H., L. B. Barber, R. L. Runkel, J. N. Ryan, D. M. McKnight, and R. D. Wass (2004), Conservative and reactive solute transport in constructed wetlands, Water Resour. Res., 40, W01201, doi:10.1029/2003WR002130.