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Ecohydrological factors affecting nitrate concentrations in a phreatic desert aquifer in northwestern China

Environmental Science and Technology

By:
, , and
DOI: 10.1021/es702478d

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Abstract

Aerobic conditions in desert aquifers commonly allow high nitrate (NO 3-) 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- (??15N NO3 and ??18ONO3) were used to trace NO3- cycling processes which affect concentrations in groundwater and unsaturated zone moisture in the arid Badain Jaran Oesert in northwestern China. Most groundwater NO3- appears to be depleted relative to Cl- in rainfall concentrated by evapotranspiration, indicating net N losses. Unsaturated zone NO 3- is generally higher than groundwater NO 3- in terms of both concentration (up to 15 476 ??M, 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. ?? 2008 American Chemical Society.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Ecohydrological factors affecting nitrate concentrations in a phreatic desert aquifer in northwestern China
Series title:
Environmental Science and Technology
DOI:
10.1021/es702478d
Volume
42
Issue:
10
Year Published:
2008
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Environmental Science and Technology
First page:
3531
Last page:
3537
Number of Pages:
7