Isotopic evidence that recent agriculture overprints climate variability in nitrogen deposition to the Tibetan Plateau

Zhengjie Li; Meredith G. Hastings; Wendell W. Walters; Lide Tian; Steven C. Clemens; Linlin Song; Lili Shao; Yunting Fang

Environment International (May 2020)

Isotopic evidence that recent agriculture overprints climate variability in nitrogen deposition to the Tibetan Plateau

Zhengjie Li,
Meredith G. Hastings,
Wendell W. Walters,
Lide Tian,
Steven C. Clemens,
Linlin Song,
Lili Shao,
Yunting Fang

Affiliations

Zhengjie Li: CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning 110016, China; Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island 02912, USA; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; Key Laboratory of Stable Isotope Techniques and Applications, Shenyang, Liaoning 110016, China
Meredith G. Hastings: Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island 02912, USA; Institute at Brown for Environment and Society, Brown University, Providence, Rhode Island 02912, USA; Corresponding authors at: Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island 02912, USA (M.G. Hastings). CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning 110016, China (Y. Fang).
Wendell W. Walters: Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island 02912, USA; Institute at Brown for Environment and Society, Brown University, Providence, Rhode Island 02912, USA
Lide Tian: Institute of International Rivers and Eco-Security, Yunnan University, Kunming, Yunnan 650500, China; Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100101, China
Steven C. Clemens: Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island 02912, USA
Linlin Song: CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning 110016, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; Key Laboratory of Stable Isotope Techniques and Applications, Shenyang, Liaoning 110016, China
Lili Shao: Institute of International Rivers and Eco-Security, Yunnan University, Kunming, Yunnan 650500, China
Yunting Fang: CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning 110016, China; Qingyuan Forest CERN, Shenyang, Liaoning 110016, China; Key Laboratory of Stable Isotope Techniques and Applications, Shenyang, Liaoning 110016, China; Corresponding authors at: Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island 02912, USA (M.G. Hastings). CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning 110016, China (Y. Fang).

Journal volume & issue: Vol. 138

Abstract

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The stable isotopes of nitrogen in nitrate archived in polar ice have been interpreted as reflecting a shift in reactive nitrogen sources or changes in atmospheric chemical reactivity. Here, we present a novel concentration and isotopic record of nitrate (δ15N-NO3−) from a central Tibetan Plateau ice core over the last ~200 years. We find that nitrate concentration increased from 6.0 ± 2.3 μeq/L (mean ± 1σ) in the preindustrial period (prior to 1900s) to 7.3 ± 2.7 μeq/L in post-1950. Over the same time period, the δ15N-NO3− decreased from 8.7 ± 3.7‰ to 4.2 ± 3.1‰, with much larger interannual variation in δ15N-NO3− during the preindustrial period. We present a useful framework for quantifying the sensitivity of the isotopic composition of atmospheric nitrate to changes in both sources and chemistry (gas and aerosol phase). After 1950, nitrogen deposition is primarily driven by fertilizer use, leading to significant increases in concentration and decreases in δ15N-NO3−. The large interannual variability of ice core δ15N-NO3− in the preindustrial reflects natural processes, namely the El Niño Southern Oscillation (ENSO) and dust events. Our results highlight a new connection between the nitrogen cycle and ENSO, and the overprinting of natural climate signals by recent anthropogenic increases in reactive nitrogen release. Keywords: Ice core, Nitrogen stable isotope, Agriculture NOx emissions, Climate variability

Published in Environment International

ISSN: 0160-4120 (Print)
Publisher: Elsevier
Country of publisher: United Kingdom
LCC subjects: Geography. Anthropology. Recreation: Environmental sciences
Website: https://www.journals.elsevier.com/environment-international

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