HR: 10:55h
AN: H22B-03 INVITED     [Abstracts]
TI: Contrasts in Flushing Patterns Among Solutes
AU: * Shanley, J B
EM: jshanley@usgs.gov
AF: U.S. Geological Survey, P.O. Box 628, Montpelier, VT 05601 United States
AU: Sebestyen, S D
EM: sds@nature.berkeley.edu
AF: SUNY - Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY 13210 United States
AU: Boyer, E W
EM: boyer@nature.Berkeley.EDU
AF: University of California, 140 Mulford Hall # 3114, Berkeley, CA 94720 United States
AU: Ross, D S
EM: dross@uvm.edu
AF: University of Vermont, Hills Building, Burlington, VT 05405 United States
AB: High-frequency sampling since 1991 at the 41-ha forested W-9 catchment at Sleepers River, Vermont provides a wealth of data to evaluate catchment flushing responses. Snowmelt and rain-on-snow account for about half the annual flow at Sleepers River during a 6-week period in early spring. Summer and fall storms produce frequent high-flows of short duration. Flushing of weathering products (Ca, Mg, Na, K, SO₄ ANC, Si) is generally supply-limited, and is masked by rapid dilution with meteoric and soil water during events. In contrast, flushing dominates the stream dynamics of atmospheric and pedogenic solutes (NO₃, DOC, Hg), causing concentration increases with increasing flow. During snowmelt, NO₃ peaks well before the peak in discharge, whereas DOC tracks discharge closely and peaks concurrently. These patterns suggest that NO₃ is supply-limited and DOC is transport-limited; W-9 is not N saturated and the available NO₃ supply is readily leached from the soil, whereas stream DOC progressively increases as rising water tables and expanding saturated areas connect with new source areas. In summer storms, DOC and NO₃ both peak simultaneously with discharge. Unlike DOC, however, NO₃ concentrations are attenuated with subsequent storms that follow within a few days, consistent with a depletion of the NO₃ pool available for flushing as observed during snowmelt. Sleepers River contrasts with the Snake River in Colorado, where NO₃ and DOC reverse roles; DOC peaks early in snowmelt and may be supply-limited due to the paucity of organic matter. An ample supply of NO₃ is available due to N saturation and N fixation, but NO₃ may be transport-limited due to primary N sources in talus deposits far from the stream. Hg is an atmospheric solute that accumulates in soils because of its affinity for organic matter, and is flushed by high flows, mostly in association with suspended sediment. The concept of flushing provides a useful context for understanding the variable responses of solutes to the expansion of catchment saturation during high flow events.
DE: 0428 Carbon cycling (4806)
DE: 0469 Nitrogen cycling
DE: 1830 Groundwater/surface water interaction
DE: 1879 Watershed
SC: Hydrology [H]
MN: Fall Meeting 2005