HR: 1340h
AN: H13F-1379    [Abstracts]
TI: Tracing Sources of Organic Matter and Nitrate in the San Francisco Bay-Delta-River Ecosystem Using Isotopic Techniques: Comparison of Insights Gained from Fixed-site, Synoptic, and Diel Sampling Strategies
AU: * Kendall, C
EM: ckendall@usgs.gov
AF: USGS, 345 Middlefield Road, MS 434, Menlo Park, CA 94025 United States
AU: Silva, S R
EM: srsilva@usgs.gov
AF: USGS, 345 Middlefield Road, MS 434, Menlo Park, CA 94025 United States
AU: Doctor, D H
EM: dhdoctor@usgs.gov
AF: USGS, 345 Middlefield Road, MS 434, Menlo Park, CA 94025 United States
AU: Wankel, S D
EM: sdwankel@usgs.gov
AF: USGS, 345 Middlefield Road, MS 434, Menlo Park, CA 94025 United States
AU: Chang, C C
EM: ccchang@usgs.gov
AF: USGS, 345 Middlefield Road, MS 434, Menlo Park, CA 94025 United States
AU: Bergamaschi, B A
EM: bbergama@usgs.gov
AF: USGS, 6000 J Street, Placer Hall, Sacramento, CA 95819 United States
AU: Kratzer, C R
EM: ckratzer@usgs.gov
AF: USGS, 6000 J Street, Placer Hall, Sacramento, CA 95819 United States
AU: Dahlgren, R A
EM: radahlgren@ucdavis.edu
AF: UC-Davis, Dept of Civil & Environmental Engineering, Davis, CA 95616 United States
AU: Fleenor, W E
EM: wefleenor@ucdavis.edu
AF: UC-Davis, Dept of Land, Air and Water Resources, Davis, CA 95616 United States
AB: Understanding the sources and sinks for organics and nitrate is critical for devising effective strategies to reduce their loads in ecosystems and mitigate local problems of low dissolved oxygen levels and/or production of disinfection byproducts during water treatment. Since isotopic techniques are effective methods for quantifying the sources and sinks of organics and nutrients, we have analyzed particulate organic matter (POM), nitrate, dissolved inorganic and organic carbon (DIC, DOC), and water isotope samples from selected sites since 2000. Our studies indicate that isotope data are a useful adjunct to traditional methods for assessing and monitoring sources of organics and nutrients. The original sampling in 2000-2001 used the classical fixed-site and fixed-time interval sampling approach, where sites on the San Joaquin River and its major tributaries were sampled bimonthly from July to October for chemistry and isotopes (Kratzer et al., 2004: see URL below). Subsequently, samples were collected during 4 transects along the San Joaquin River (10/02, 3/03, 9/03, and 7/04); the first and last of these transects extended through the Delta to the Bay. Several sites were sampled during diel studies in 8/04 and 7/05. Although fixed-site sampling is the norm in watershed studies, we have found that isotope and chemical data collected during longitudinal transects of the river and diel sampling of several sites along short river reaches have been more useful in convincing colleagues that isotope measurements are extremely useful adjuncts to traditional methods for assessing and monitoring sources of organics and nutrients during ecosystem restoration programs. Furthermore, we have concluded that while the obvious value of isotopes for water resources management is to tell us things about water resources that we didn't know before, what convinces the skeptic is when the isotopes tell us things about water resources that contradict what we thought we knew before. This work will highlight these and other insights developed using varied sampling strategies, and suggest guidelines for how to approach future studies in biologically active and human impacted rivers like the San Joaquin River system.
UR: http://water.usgs.gov/pubs/wri/wri034127/
DE: 0330 Geochemical cycles (1030)
DE: 0438 Diel, seasonal, and annual cycles (4227)
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: Fall Meeting 2005