Tuesday, May 27, 2008 - 9:30 AM
137

Dissolved organic carbon in streams: Fluxes, impervious surfaces, and hydrologic drivers along an urban stream continuum

Kenneth T. Belt1, Sujay S. Kaushal2, Christopher Swan3, Richard V. Pouyat1, and Peter M. Groffman4. (1) Northern Research Station, U.S.D.A. Forest Service, 5200 Westland Blvd, Baltimore, MD 21227, (2) Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, 1 Williams Street, P.O. Box 38, Solomons, MD 20688, (3) Geography and Environmental Systems, University of Maryland, Baltimore County, Baltimore, MD 21250, (4) Institute of Ecosystem Studies, P.O. Box AB, Route 44A, Millbrook, NY 12545

Two years of approximately bi-weekly sampling of two forested reference and three urban streams (210 samples) of the BES Long Term Ecological Research network revealed that DOC concentrations & fluxes were a function of both impervious cover (ISC) and hydrologic state.  DOC concentrations at the urban sites were higher than the forested reference sites for both dry weather (1.84 vs. 1.53 mg/l.) and wet weather (4.33 vs 2.54 mg/l.)   Dry weather concentrations were related to catchment ISC percentage (r^2 = 0.47), increasing from a mean of 1.53 mg/l at the reference sites to 2.49 mg/l at the most urbanized site (41 % ISC.)  Wet weather & post-wet weather concentrations were all higher than dry concentrations, and increased greatly with ISC (r^2 = 0.77), from a mean of 2.54mg/l (reference sites) to 5.51 mg/l at the 41 % ISC site.  Instantaneous areal fluxes at different sites were somewhat higher at the reference sites (12.4 g/ha/day) than the urban sites (7.0 g/ha/day.)  However, a very large increase with ISC was seen for wet weather, from a mean of 50 g/ha/day at the reference sites to 246 g/ha/day at the most urbanized site (r^2 = 0.90).  Estimated annual areal fluxes for 2005-2006 ranged from 9.8 and 5.7 kg/ha/yr (reference sites) to 24.4 kg/ha/yr at the most urban site.  While dry weather exports of DOC are similar for both forested and urban streams, ISC and its attendant network of drainage infrastructure (and strong terrestrial-aquatic linkages) may be greatly modifying wet weather related DOC fluxes, resulting in much higher exports for more urbanized catchments.  This may have significant implications for eutrophy of downstream aquatic ecosystems, pollutant transport, and disinfection by-product formation during drinking water treatment processes in urbanizing catchments.


Web Page: DOC flux, urban hydrology, storm runoff

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