A Complete Isotope (δ15N, δ18O, Δ17O) Investigation of Atmospherically Deposited Nitrate in Glacial‐Hydrologic Systems Across the Third Pole Region. Issue 19 (25th September 2020)

• Record Type: Journal Article
• Authors: Lin, Mang; Hattori, Shohei; Wang, Kun; Kang, Shichang; Thiemens, Mark H.; Yoshida, Naohiro
• Is Part Of: Journal of geophysical research. Volume 125:Issue 19(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-09-25
• Subjects: oxygen isotopic anomalies -- mass‐independent fractionation -- photolysis -- glacier melting -- Tibetan Plateau -- Himalayas; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2019JD031878
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: The Himalayas and Tibetan Plateau, identified as the Third Pole (TP), is a unique region because of its insertion into global environmental and climatic changes. Deposition of atmospheric nitrate in this region is one of the most important sources of reactive nitrogen to glacial‐hydrologic system and ecosystems. The isotopic composition of atmospherically deposited nitrate preserved in ice bodies plays a central role in delineating environmental and climatic changes, present, and past. Here, we provide an overview of the complete isotopic compositions (δ 15 N, δ 18 O, and Δ 17 O) of nitrate in aerosol, snow, ice, and water samples ( n = 46) collected across the Southern, Southeastern, Central, and Northern TP to constrain complex nitrogen cycles of the atmosphere, cryosphere, hydrosphere, and, potentially, the biosphere. A large variability of snow nitrate isotopic compositions is observed across the TP at different spatial scales (from a single glacier to the entire plateau), likely due to the complex landscape and relevant physical and chemical processes across the TP. Large nitrate Δ 17 O values are observed in water samples collected from the Mt. Everest region, highlighting the considerable fraction (up to 45%) of atmospheric nitrate to the nitrate load in this Himalayan hydrologic system. Our work reveals the complex chemical, depositional, and postdepositional processes over the TP that are greater than previously thought and identifies further comprehensive investigations, which entail using nitrate isotopic compositions as an identifier for nitrate source apportionment in various ecosystems and understanding past atmospheric and climatic conditions in this region. Key Points: Complete isotopic compositions of nitrate in aerosol, snow, ice, and water samples collected across the Tibetan Plateau were measured Nitrate isotopic compositions in the cryosphere over the Tibetan Plateau is spatially highly heterogeneous Contribution of atmospheric nitrates to the hydrologic system is high at Himalayas