thumbnail

Nitrate dynamics within the Pajaro River, a nutrient-rich, losing stream

Journal of the North American Benthological Society

By:
, , , , , , ,
DOI: 10.1899/0887-3593(2007)26[191:NDWTPR]2.0.CO;2

Links

Abstract

The major ion chemistry of water from an 11.42-km reach of the Pajaro River, a losing stream in central coastal California, shows a consistent pattern of higher concentrations during the 2nd (dry) half of the water year. Most solutes are conserved during flow along the reach, but [NO 3-] decreases by ???30% and is accompanied by net loss of channel discharge and extensive surface-subsurface exchange. The corresponding net NO3- uptake length is 37 ?? 13 km (42 ?? 12 km when normalized to the conservative solute Cl-), and the areal NO3- uptake rate is 0.5 ??mol m -2 s-1. The observed reduction in [NO3-] along the reach results from one or more internal sinks, not dilution by ground water, hill-slope water, or other water inputs. Observed reductions in [NO3-] and channel discharge along the experimental reach result in a net loss of 200-400 kg/d of NO3--N, ???50% of the input load. High-resolution (temporal and spatial) sampling indicates that most of the NO3- loss occurs along the lower part of the reach, where there is the greatest seepage loss and surface-subsurface exchange of water. Stable isotopes of NO 3-, total dissolved P concentrations, and streambed chemical profiles suggest that denitrification is the most significant NO 3- sink along the reach. Denitrification efficiency, as expressed through downstream enrichment in 15N-NO3-, varies considerably during the water year. When discharge is greater (typically earlier in the water year), denitrification is least efficient and downstream enrichment in 15N-NO3- is greatest. When discharge is lower, denitrification in the streambed appears to occur with greater efficiency, resulting in lower downstream enrichment in 15N-NO3-. ?? 2007 by The North American Benthological Society.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Nitrate dynamics within the Pajaro River, a nutrient-rich, losing stream
Series title:
Journal of the North American Benthological Society
DOI:
10.1899/0887-3593(2007)26[191:NDWTPR]2.0.CO;2
Volume
26
Issue:
2
Year Published:
2007
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
191
Last page:
206
Number of Pages:
16