Episodic, seasonal, and annual export of atmospheric and microbial nitrate from a temperate forest. Issue 2 (19th January 2016)

• Record Type: Journal Article
• Authors: Sabo, Robert D.; Nelson, David M.; Eshleman, Keith N.
• Is Part Of: Geophysical research letters. Volume 43:Issue 2(2016)
• Page Start: 683
• Page End: 691
• Publication Date: 2016-01-19
• Subjects: nitrate -- temperate forest -- atmospheric nitrate -- atmospheric N deposition -- stable isotopes -- microbial nitrate; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2015GL066758
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: It remains difficult to assess the timing and amount of atmospherically deposited and microbial nitrate (NO3 ‐NAtm and NO3 ‐NMicro, respectively) reaching streams. To elucidate temporal variation of NO3 ‐NAtm and NO3 ‐NMicro, we measured nitrate concentrations, δ 17 O‐NO3 −, and δ 18 O‐NO3 − in a stream draining a gaged, forested watershed in the central Appalachian Mountains throughout a range of hydrological conditions during two water years. From the isotopic data we calculated Δ 17 O‐NO3 − values, which were used to calibrate a statistical load model to estimate export of NO3 ‐NAtm and NO3 ‐NMicro . A hydrograph separation was used to estimate loss of NO3 ‐NAtm and NO3 ‐NMicro through base flow and direct runoff pathways. NO3 ‐NAtm contributed 7–11% of the total nitrate yields and paralleled seasonal patterns of NO3 ‐NMicro . Yields of NO3 ‐NAtm and NO3 ‐NMicro in streamflow during the study period were dominated (61 and 85%, respectively) by base flow transport, suggesting that base flow is a major loss pathway for both nitrate species from this watershed. Key Points: Microbial and atmospheric nitrate detected in base flow and direct runoff Intra‐annual and inter-annual variation in yield of microbial and atmospheric nitrate Base flow is an important loss pathway for microbial and atmospheric nitrate