1 / 24

Mercury and Organic Carbon Dynamics in an Upland Landscape during Snowmelt

Mercury and Organic Carbon Dynamics in an Upland Landscape during Snowmelt. Jamie Shanley 1 Paul Schuster 2 Mike Reddy 2 Dave Roth 2 Howard Taylor 2 George Aiken 2 1 U.S. Geological Survey Montpelier, Vermont 2 U.S. Geological Survey, Boulder, Colorado. Objectives.

mala
Download Presentation

Mercury and Organic Carbon Dynamics in an Upland Landscape during Snowmelt

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Mercury and Organic Carbon Dynamics in an Upland Landscape during Snowmelt Jamie Shanley1 Paul Schuster2 Mike Reddy2 Dave Roth2 Howard Taylor2 George Aiken2 1U.S. Geological Survey Montpelier, Vermont 2 U.S. Geological Survey, Boulder, Colorado

  2. Objectives • Develop and test methodologies for intensive spatial and temporal event sampling of Hg • Investigate the dynamics of Hg transport during snowmelt across a gradient of land cover and watershed size • Evaluate linkages between dissolved and particulate Hg and dissolved and particulate carbon

  3. Previous Hg research in Vermont • Wet and dry deposition measurements in Underhill since 1993 - world’s longest continuous record. • High Hg in leaffall (Rae, 1998) corroborates high Hg in dry deposition (up to 5x wet) (Scherbatskoy et al., 1998) • Hg deposition retained (>90%) in terrestrial watershed; export episodic, associated with POC (Scherbatskoy et al., 1998; Shanley et al,. 1999) • High Hg in O-horizon soil solution, associated w/DOC (Donlon, 1999) • Hg export in agricultural landscape similar to forest (Rinehart, 2000) • Routine measurements by State since 1970s show high Hg in fish • Current focused study of sediment, water and fish Hg in VT lakes (Kamman et al., 1998; 2000)

  4. Sleepers River Research Watershed • USDA Agricultural Research Service 1957-1975 • Established 17 stream gages, 13 meteorological stations • National Weather Service 1968-1986 • Snowmelt modeling - energy balance approach • Cold Regions Lab (CRREL) 1979-present • Snowmelt modeling, sensor testing • US Geological Survey 1991-present • Water, Energy, and Biogeochemical Budgets (WEBB)

  5. Sleepers River Research Watershed Basin characteristics • Elevation: 200 to 690 m, slopes gentle to very steep • Precipitation: 1100 mm per year, ~30% as snow • Climate: Humid continental, Mean annual T: 6°C • Gaged watersheds from 3.4 ha to 111 km2 • Land cover - overall 2/3 forested, 1/3 open land • Mixed / Northern hardwoods (Sugar maple, beech, ash, spruce/fir) • Dairy farming (pasture, hayfields, corn fields) • Economics: Dairy farming, maple sugaring, logging

  6. Sleepers River Research Watershed Basin characteristics • Bedrock: quartz-mica phyllite with beds of calcareous granulite • Surficial: 1-3 m of dense basal till from local bedrock • Soils: Inceptisols, spodosols, and histosols w/wetlands • Stream chemistry: well-buffered calcium bicarbonate / sulfate waters • Hydrology: Flashy streams, snowmelt dominated

  7. W-5 11,125 ha (67%) W-3 837 ha (80%) W-2 59 ha (27%) W-9 41 ha (100%) W-9A 17 ha (100%) W-9B 13 ha (100%) W-9C 7 ha (100%) W-9BX 5.1 ha (100%) W-9BY 3.4 ha (100%) W-9BXA ~2 ha (100%) Study watersheds(with % of area forested)

  8. W-9 watershed

  9. Field procedures • Streamwater • Grab sample in teflon holding bottle for Hg - collected wearing particle-free gloves. • Grab sample in pre-baked amber glass bottle for C fractions. • Grab sample in PE bottle for major ions • Field sonde for Temp., pH, DO, Sp. Cond., ORP • Snow • Lexan scoop into PE bag while wearing particle-free gloves; 7 profiles at peak snowpack • Groundwater and seeps • Peristaltic pump with teflon tubing - 6 samples near peak melt

  10. On-site sample processing Field laboratory - within 4 hours - complete duplicate processing of all samples • Mercury • Dissolved:Vacuum filtered through 0.4-µm cellulose acetate membrane into acid- washed 125-mL glass bottle. Acidified with K2Cr2O7. • Particulate: Filter membrane placed in 60-mL glass bottle, filled with DI water, acidified with K2Cr2O7 • Carbon • DOC: Vacuum filtered through 0.7-µm GFF (glass fiber) filter into pre-baked amber bottles • POC: I set of duplicate filter membranes wrapped in Al foil for solid C analysis; additional set saved for LOI determination. • Major ions • Cations: syringe-filtered through 0.4-µm cellulose acetate membrane into acid-washed 125-mL PE bottle. Acidified to pH 2 with HNO3 • Anions: syringe-filtered through 0.4-µm cellulose acetate membrane into clean 125-mL PE bottle. Kept chilled.

  11. Laboratory Analysis All analyses except POC, PON at USGS, Boulder, CO • Mercury • Dissolved:Cold vapor atomic fluorescence spectrometry (CVAFS) on filtered aliquot. • Particulate: CVAFS on acidified solution containing filter membrane . • Carbon • DOC (and TOC): Ultraviolet persulfate oxidation with infrared detection • POC (and PON) at Chesapeake Biological Lab, University of Maryland • Loss-on-ignition (LOI) to estimate organic C by combustion at 550 C.. • SUVA - Absorbance at 254 µm • Major ions • Cations: ICP • Anions: Ion chromatography • Alkalinity: Gran titration.

  12. Hg concentration ranges and results of duplicate analyses Based on 66 duplicate analyses Concentrations, ng/LDuplicates median min max mean % diff. Hg, dissolved 0.9 <0.3 4.1 5.8 Hg, particulate 2.3 0.6 16.3 12

  13. Hg vs. alkalinity, all sites, Sleepers River snowmelt 2000

  14. DOC vs. discharge, all sites, Sleepers River snowmelt 2000

  15. Particulate Hg vs. POC, all sites, Sleepers River snowmelt 2000

  16. Hg vs. discharge, all sites, Sleepers River snowmelt 2000

  17. Dissolved Hg vs. DOC, all sites, Sleepers River snowmelt 2000

  18. Specific discharge and DOC at W-9B (forested, 13 ha)

  19. Dissolved and particulate Hg at W-9B

  20. Dissolved Hg and DOC at W-9B

  21. Dissolved Hg and DOC at W-9B

  22. DOC vs. Hg flushing, all sites

  23. Conclusions • We developed a methodology for accurate and reproducible sampling of Hg at high temporal frequency using ultraclean sample handling protocols • Dissolved and particulate Hg concentrations closely tracked the respective dissolved and particulate C fractions, despite 6 order-of-magnitude difference in concentrations • Hg and C may be biogeochemically linked, or they simply have a common source -- shallow soil -- that is flushed during snowmelt. Needs further research.

More Related