![]() ![]()
|
![]() |
|
|||||||
![]() |
|
a USGS, 345 Middlefield Rd., Menlo Park, CA 94025
b USGS, 12201 Sunrise Valley Dr., Reston, VA 20192
c USGS, 6000 J St., Placer Hall, Sacramento, CA 95819
d USGS, 810 Bear Tavern Rd., West Trenton, NJ 08628
e J.M. Denver, USGS, 1289 McD Dr., Dover, Delaware 19901
f USGS, 10615 SE Cherry Blossom Dr., Portland, OR 97216
* Corresponding author (ctgreen{at}usgs.gov).
Received for publication September 29, 2006. The ability of natural attenuation to mitigate agricultural nitrate contamination in recharging aquifers was investigated in four important agricultural settings in the United States. The study used laboratory analyses, field measurements, and flow and transport modeling for monitoring well transects (0.5 to 2.5 km in length) in the San Joaquin watershed, California, the Elkhorn watershed, Nebraska, the Yakima watershed, Washington, and the Chester watershed, Maryland. Ground water analyses included major ion chemistry, dissolved gases, nitrogen and oxygen stable isotopes, and estimates of recharge date. Sediment analyses included potential electron donors and stable nitrogen and carbon isotopes. Within each site and among aquifer-based medians, dissolved oxygen decreases with ground water age, and excess N2 from denitrification increases with age. Stable isotopes and excess N2 imply minimal denitrifying activity at the Maryland and Washington sites, partial denitrification at the California site, and total denitrification across portions of the Nebraska site. At all sites, recharging electron donor concentrations are not sufficient to account for the losses of dissolved oxygen and nitrate, implying that relict, solid phase electron donors drive redox reactions. Zero-order rates of denitrification range from 0 to 0.14 µmol N L–1d–1, comparable to observations of other studies using the same methods. Many values reported in the literature are, however, orders of magnitude higher, which is attributed to a combination of method limitations and bias for selection of sites with rapid denitrification. In the shallow aquifers below these agricultural fields, denitrification is limited in extent and will require residence times of decades or longer to mitigate modern nitrate contamination.
Abbreviations: AVS, acid volatile sulfide CA, California CFC, chlorofluorocarbon CFIRMS, continuous-flow isotope-ratio mass spectrometry DOC, dissolved organic carbon IN, Indiana MD, Maryland NE, Nebraska WA, Washington
This article has been cited by other articles:
![]() |
![]() |
![]() |
![]() |
![]() ![]() L. M. Debrewer, S. W. Ator, and J. M. Denver Temporal Trends in Nitrate and Selected Pesticides in Mid-Atlantic Ground Water J. Environ. Qual., September 2, 2008; 37(5_Supplement): S-296 - S-308. [Abstract] [Full Text] [PDF] ![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() ![]() P. D. Capel, K. A. McCarthy, and J. E. Barbash National, Holistic, Watershed-Scale Approach to Understand the Sources, Transport, and Fate of Agricultural Chemicals J. Environ. Qual., May 1, 2008; 37(3): 983 - 993. [Abstract] [Full Text] [PDF] ![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() ![]() L. J. Puckett, C. Zamora, H. Essaid, J. T. Wilson, H. M. Johnson, M. J. Brayton, and J. R. Vogel Transport and Fate of Nitrate at the Ground-Water/Surface-Water Interface J. Environ. Qual., May 1, 2008; 37(3): 1034 - 1050. [Abstract] [Full Text] [PDF] ![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() ![]() C. T. Green, L. H. Fisher, and B. A. Bekins Nitrogen Fluxes through Unsaturated Zones in Five Agricultural Settings across the United States J. Environ. Qual., May 1, 2008; 37(3): 1073 - 1085. [Abstract] [Full Text] [PDF] ![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() ![]() G. V. Steele, H. M. Johnson, M. W. Sandstrom, P. D. Capel, and J. E. Barbash Occurrence and Fate of Pesticides in Four Contrasting Agricultural Settings in the United States J. Environ. Qual., May 1, 2008; 37(3): 1116 - 1132. [Abstract] [Full Text] [PDF] ![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() ![]() J. H. Duff, A. J. Tesoriero, W. B. Richardson, E. A. Strauss, and M. D. Munn Whole-Stream Response to Nitrate Loading in Three Streams Draining Agricultural Landscapes J. Environ. Qual., May 1, 2008; 37(3): 1133 - 1144. [Abstract] [Full Text] [PDF] ![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
![]() ![]() J. L. Domagalski, S. Ator, R. Coupe, K. McCarthy, D. Lampe, M. Sandstrom, and N. Baker Comparative Study of Transport Processes of Nitrogen, Phosphorus, and Herbicides to Streams in Five Agricultural Basins, USA J. Environ. Qual., May 1, 2008; 37(3): 1158 - 1169. [Abstract] [Full Text] [PDF] ![]() |
![]() |
HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |