Document Detail


Ecohydrological factors affecting nitrate concentrations in a phreatic desert aquifer in northwestern China.
MedLine Citation:
PMID:  18546685     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Aerobic conditions in desert aquifers commonly allow high nitrate (NO3-) concentrations in recharge to persist for long periods of time, an important consideration for N-cycling and water quality. In this study, stable isotopes of NO3- (delta15N(NO3) and delta18O(NO3)) were used to trace NO3- cycling processes which affect concentrations in groundwater and unsaturated zone moisture in the arid Badain Jaran Desert in northwestern China. Most groundwater NO3- appears to be depleted relative to Cl- in rainfall concentrated by evapotranspiration, indicating net N losses. Unsaturated zone NO3- is generally higher than groundwater NO3- in terms of both concentration (up to 15 476 microM, corresponding to 3.6 mg NO3(-)-N per kg sediment) and ratios with Cl-. Isotopic data indicate that the NO3- derives primarily from nitrification, with a minor direct contribution of atmospheric NO3- inferred for some samples, particularly in the unsaturated zone. Localized denitrification in the saturated zone is suggested by isotopic and geochemical indicators in some areas. Anthropogenic inputs appear to be minimal, and variability is attributed to environmental factors. In comparison to other arid regions, the sparseness of vegetation in the study area appears to play an important role in moderating unsaturated zone NO3- accumulation by allowing solute flushing and deterring extensive N2 fixation.
Authors:
John B Gates; John Karl Böhlke; W Mike Edmunds
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Environmental science & technology     Volume:  42     ISSN:  0013-936X     ISO Abbreviation:  Environ. Sci. Technol.     Publication Date:  2008 May 
Date Detail:
Created Date:  2008-06-12     Completed Date:  2008-11-17     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0213155     Medline TA:  Environ Sci Technol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3531-7     Citation Subset:  IM    
Affiliation:
Oxford University Centre for Water Research, Dyson Perrins Building, South Parks Road, Oxford OX1-3QY, UK. john.gates@stcatz.oxon.org
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MeSH Terms
Descriptor/Qualifier:
China
Ecology*
Nitrates / analysis*
Water Pollutants, Chemical / analysis*
Chemical
Reg. No./Substance:
0/Nitrates; 0/Water Pollutants, Chemical

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