Discovery of a large subsoil nitrate reservoir in an arroyo floodplain and associated aquifer contamination

Geology
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Abstract

In an area of elevated nitrate (NO3) groundwater concentrations in the northern Chihuahuan Desert in central New Mexico (United States), a large reservoir of nitrate was found in the subsoil of an arroyo floodplain. Nitrate inventories in the floodplain subsoils ranged from 10,000 to 38,000 kg NO3-N/ha—over twice as high as any previously measured arid region. The floodplain subsoil NO3 reservoir was over 100 times higher than the adjacent desert (59–95 kg NO3-N/ha). Chloride mass balance calculations of subsoils indicate arroyo floodplain subsoils have undergone negative recharge since 2600–8600 yr ago, while the surrounding desert has had negative recharge since 13,000–17,000 yr ago. Compared to the adjacent desert, plant communities are larger and more abundant in the floodplain, though subsoil NO3 is apparently not utilized. We demonstrate that NO3 accumulates in the subsoil of the floodplain through evaporation of monsoon season precipitation funneled into the arroyo. Through a one-dimensional vadose zone model, we show that the NO3 inventories in the arroyo floodplain could be acquired 8 to 75 times faster than through atmospheric deposition through the lateral movement

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Publication type Article
Publication Subtype Journal Article
Title Discovery of a large subsoil nitrate reservoir in an arroyo floodplain and associated aquifer contamination
Series title Geology
DOI 10.1130/G47916.1
Edition Online First
Year Published 2021
Language English
Publisher Geological Society of America
Contributing office(s) New Mexico Water Science Center
Country United States
State New Mexico
Other Geospatial Chihuahuan Desert
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