Relations of hydrogeologic factors, groundwater reduction-oxidation conditions, and temporal and spatial distributions of nitrate, Central-Eastside San Joaquin Valley, California, USA

Hydrogeology Journal
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Abstract

In a 2,700-km2 area in the eastern San Joaquin Valley, California (USA), data from multiple sources were used to determine interrelations among hydrogeologic factors, reduction-oxidation (redox) conditions, and temporal and spatial distributions of nitrate (NO3), a widely detected groundwater contaminant. Groundwater is predominantly modern, or mixtures of modern water, with detectable NO3 and oxic redox conditions, but some zones have anoxic or mixed redox conditions. Anoxic conditions were associated with long residence times that occurred near the valley trough and in areas of historical groundwater discharge with shallow depth to water. Anoxic conditions also were associated with interactions of shallow, modern groundwater with soils. NO3 concentrations were significantly lower in anoxic than oxic or mixed redox groundwater, primarily because residence times of anoxic waters exceed the duration of increased pumping and fertilizer use associated with modern agriculture. Effects of redox reactions on NO3 concentrations were relatively minor. Dissolved N2 gas data indicated that denitrification has eliminated >5 mg/L NO3–N in about 10% of 39 wells. Increasing NO3 concentrations over time were slightly less prevalent in anoxic than oxic or mixed redox groundwater. Spatial and temporal trends of NO3 are primarily controlled by water and NO3 fluxes of modern land use.
Publication type Article
Publication Subtype Journal Article
Title Relations of hydrogeologic factors, groundwater reduction-oxidation conditions, and temporal and spatial distributions of nitrate, Central-Eastside San Joaquin Valley, California, USA
Series title Hydrogeology Journal
DOI 10.1007/s10040-011-0750-1
Volume 19
Issue 6
Year Published 2011
Language English
Publisher Springer
Publisher location Amsterdam, Netherlands
Contributing office(s) California Water Science Center
Description 22 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Hydrogeology Journal
First page 1203
Last page 1224
Country United States
State California
Other Geospatial Central-eastside San Joaquin Valley
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