Enriched groundwater seeps in two Vermont headwater catchments are hotspots of nitrate turnover

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Groundwater seeps in upland catchments are often enriched relative to stream waters, higher in pH, Ca2+ and sometimes NO3¯. These seeps could be a NO3¯ sink because of increased denitrification potential but may also be ‘hotspots’ for nitrification because of the relative enrichment. We compared seep soils with nearby well-drained soils in two upland forested watersheds in Vermont that are sites of ongoing biogeochemical studies. Gross N transformation rates were measured over three years along with denitrification rates in the third year. Gross ammonification rates were not different between the seep and upland soils but gross nitrification rates were about 3 × higher in the seep soils. Net nitrification rates trended higher in the upland soils and NO3¯ consumption (gross—net) was 8 times higher in the seep soils. The average denitrification rate for seep soils was about equal to the difference in NO3¯ consumption between seep and upland soils, suggesting denitrification can make up the difference. Temporal variation in seep water NO3¯ concentration was correlated with watershed outlet NO3¯ concentration. However, it is not clear that in-seep processes greatly altered seep water NO3¯ contribution to the streams. Seep soils appear to be hotspots of both nitrification and denitrification.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Enriched groundwater seeps in two Vermont headwater catchments are hotspots of nitrate turnover
Series title Wetlands
DOI 10.1007/s13157-016-0733-z
Volume 36
Issue 2
Year Published 2016
Language English
Publisher Springer
Contributing office(s) New England Water Science Center
Description 13 p.
First page 237
Last page 249
Country United States
State Vermont
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