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This content will become publicly available on February 24, 2017

Title: Phytoremediation of a nitrogen-contaminated desert soil by native shrubs and microbial processes

Here, we combined phytoremediation and soil microbial nitrification and denitrification cycles to reduce nitrate and ammonium levels at a former uranium mill site near Monument Valley, Arizona. Ammonia used in uranium extraction was present throughout the soil profile. Sulfate,applied as sulfuric acid to solubilize uranium, was also present in the soil. These contaminants were leaching from a denuded area where a tailings pile had been removed and were migrating away from the site in groundwater. We planted the source area with two deep-rooted native shrubs, Atriplex cansescens and Sarcobatus vermiculatus, and irrigated transplants for 11 years at 20% the rate of potential evapotranspiration to stimulate growth, then discontinued irrigation for 4 years. Over 15 years, total nitrogen levels dropped 82%, from 347 to 64 mg kg–1. Analysis of δ15N supported our hypothesis that coupled microbial nitrification and denitrification processes were responsible for the loss of N. Soil sulfate levels changed little; however, evapotranspiration reduced sulfate leaching into the aquifer. For arid sites where traditional pump-and-treat methods are problematic, the Monument Valley data suggest that alternatives that incorporate native plants and rely on vadose zone biogeochemistry and hydrology could be a sustainable remediation for nitrogen contaminated soil.
Authors:
 [1] ;  [2] ;  [3]
  1. Univ. of Arizona, Tucson, AZ (United States)
  2. Univ. of Arizona, Tucson, AZ (United States); M3 Engineering and Technology Corp., Tucson, AZ (United States)
  3. Navarro Research and Engineering, Grand Junction, CO (United States)
Publication Date:
OSTI Identifier:
1251197
Grant/Contract Number:
LM0000421
Type:
Accepted Manuscript
Journal Name:
Land Degradation and Development
Additional Journal Information:
Journal Volume: 44; Journal Issue: 6; Journal ID: ISSN 1085-3278
Publisher:
Wiley
Research Org:
U.S. Department of Energy, Grand Junction, CO (United States). Office of Legacy Management.
Sponsoring Org:
USDOE Office of Legacy Management (LM), Office of Site Operations (LM-20)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES phytoremediation; denitrification; nitrification; uranium mill tailings; 15N