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A Complete Isotope (δ 15 N, δ 18 O, Δ 17 O) Investigation of Atmospherically Deposited Nitrate in Glacial‐Hydrologic Systems Across the Third Pole Region
Author(s) -
Lin Mang,
Hattori Shohei,
Wang Kun,
Kang Shichang,
Thiemens Mark H.,
Yoshida Naohiro
Publication year - 2020
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2019jd031878
Subject(s) - nitrate , glacier , snow , glacial period , hydrosphere , environmental science , plateau (mathematics) , reactive nitrogen , aerosol , ice core , environmental chemistry , atmospheric sciences , biosphere , geology , nitrogen , chemistry , climatology , ecology , geomorphology , mathematical analysis , mathematics , organic chemistry , biology
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.