Nitrate reduction during ground-water recharge, Southern High Plains, Texas

Alan E. Fryar, Stephen A. Macko, William F. Mullican, Katherine D. Romanak, Philip C. Bennett

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

Abstract

In arid and semi-arid environments, artificial recharge or reuse of wastewater may be desirable for water conservation, but NO3 - contamination of underlying aquifers can result. On the semi-arid Southern High Plains (USA), industrial wastewater, sewage, and feedlot runoff have been retained in dozens of playas, depressions that focus recharge to the regionally important High Plains (Ogallala) aquifer. Analyses of ground water, playa-basin core extracts, and soil gas in an 860-km2 area of Texas suggest that reduction during recharge limits NO3 - loading to ground water. Tritium and Cl- concentrations in ground water corroborate prior findings of focused recharge through playas and ditches. Typical δ15N values in ground water (>12.5‰) and correlations between δ15N and ln C(NO-(3)-N) suggest denitrification, but O2 concentrations ≥3.24 mg l-1 indicate that NO3 - reduction in ground water is unlikely. The presence of denitrifying and NO3 --respiring bacteria in cores, typical soil-gas δ15N values <0‰, and decreases in NO3 --N/Cl- and SO4 2-/Cl- ratios with depth in cores suggest that reduction occurs in the upper vadose zone beneath playas. Reduction may occur beneath flooded playas or within anaerobic microsites beneath dry playas. However, NO3 --N concentrations in ground water can still exceed drinking-water standards, as observed in the vicinity of one playa that received wastewater. Therefore, continued ground-water monitoring in the vicinity of other such basins is warranted. Copyright (C) 2000 Elsevier Science B.V.

Original languageEnglish
Pages (from-to)335-363
Number of pages29
JournalJournal of Contaminant Hydrology
Volume40
Issue number4
DOIs
StatePublished - Jan 15 2000

Bibliographical note

Funding Information:
The sampling and analyses described herein were conducted while A.E. Fryar and W.F. Mullican III were employed by the Bureau of Economic Geology. Work was supported by the US Department of Energy under a subgrant to grant number DE-FG04-90AL65847 (T.C. Gustavson, Principal Investigator). We appreciate the assistance of J.H. Honea and J.M. Keck in arranging access and providing data, S.W. Tweedy in conducting chemical analyses, B.R. Scanlon in guiding sampling at the Finley and TDCJ playas, the Bureau of Economic Geology drilling crew, and the landowners who granted access. We also thank M.S. Coyne, R.S. Fisher, B.R. Scanlon, R.F. Spalding, R. Boghici, and an anonymous reviewer for their constructive comments. Original versions of Figs. 1, 2, 7 and 8 were drafted by the Bureau of Economic Geology cartographic section under the direction of R.L. Dillon.

Keywords

  • Denitrification
  • Ground water
  • High Plains aquifer
  • Playas
  • Recharge
  • Texas

ASJC Scopus subject areas

  • Environmental Chemistry
  • Water Science and Technology

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