Global patterns of nitrate storage in the vadose zone
M J Ascott1, D C Gooddy2, L Wang3
1British Geological Survey, Maclean Building, Crowmarsh, Oxfordshire, OX10 8BB, UK. matta@bgs.ac.uk.
Nature Communications
|November 11, 2017
Summary
The vadose zone stores significant nitrate, impacting global nitrogen budgets and policymaking. This previously overlooked reservoir requires inclusion for accurate environmental assessments and effective agricultural management strategies.
Area of Science:
- Environmental Science
- Geochemistry
- Hydrology
Background:
- Global nitrogen budgets quantify human impacts on the nitrogen cycle.
- Current budgets do not account for nitrate stored in the vadose zone.
- The vadose zone's role as a nitrate reservoir is underappreciated.
Purpose of the Study:
- To quantify global nitrate storage in the vadose zone.
- To assess the significance of the vadose zone for nitrogen budgets.
- To inform effective environmental policymaking.
Main Methods:
- Utilized estimates of groundwater depth and nitrate leaching from 1900-2000.
- Quantified peak global vadose zone nitrate storage.
- Validated storage estimates with basin-scale, national-scale data, and groundwater nitrate observations.
Main Results:
- Peak global vadose zone nitrate storage estimated at 605-1814 Teragrams (Tg).
- Highest nitrate storage per unit area observed in North America, China, and Europe.
- Long vadose zone travel times identified in key agricultural regions.
Conclusions:
- The vadose zone is a critical, previously unaccounted for, nitrate reservoir.
- Conventional nitrogen budget approaches are inadequate for regions with significant vadose zone storage.
- Accurate policymaking requires integrating vadose zone nitrate dynamics into global nitrogen budgets.
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