Ice-core based assessment of nitrogen deposition in the central Tibetan Plateau over the last millennium

Xiang Zou; Shugui Hou; Shuangye Wu; Hongxi Pang; Ke Liu; Wangbin Zhang; Jinhai Yu; Jing Song; Renhui Huang; Yaping Liu

doi:10.1016/j.scitotenv.2021.152692

Ice-core based assessment of nitrogen deposition in the central Tibetan Plateau over the last millennium

Sci Total Environ. 2022 Mar 25:814:152692. doi: 10.1016/j.scitotenv.2021.152692. Epub 2021 Dec 30.

Authors

Xiang Zou¹, Shugui Hou², Shuangye Wu³, Hongxi Pang¹, Ke Liu¹, Wangbin Zhang¹, Jinhai Yu¹, Jing Song¹, Renhui Huang¹, Yaping Liu⁴

Affiliations

¹ School of Geography and Ocean Science, Nanjing University, Nanjing 210023, China.
² School of Geography and Ocean Science, Nanjing University, Nanjing 210023, China; School of Oceanography, Shanghai Jiao Tong University, Shanghai, 200240, China. Electronic address: shugui@nju.edu.cn.
³ Department of Geology and Environmental Geosciences, University of Dayton, Dayton, OH 45469, USA.
⁴ State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Science, Lanzhou, China.

PMID: 34974023
DOI: 10.1016/j.scitotenv.2021.152692

Abstract

Atmospheric nitrogen deposition is a unique source of bioavailable nitrogen for ecosystems in remote regions, and has vital impacts on ecological processes. Understanding variations of atmospheric nitrogen deposition in these regions remains challenging due to a lack of observations. Ice cores contain records of nitrogen species of nitrate (NO₃^-) and ammonium (NH₄⁺), hence provide valuable long-term data to study past variations of atmospheric nitrogen deposition. In this study, we present an annually resolved record of NH₄⁺ and NO₃^- over the past millennium, derived from the Zangser Kangri (ZK) ice core in the central Tibetan Plateau. The concentration peaks of NH₄⁺ and NO₃^- coincide with those of Ca²⁺ (a dust tracer), indicating that variation of nitrogen species in the ZK ice core is largely driven by dust activities. An EOF analysis for all chemical species (Cl^-, SO₄^2-, NO₃^-, Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺) reveals significant but separate loadings of NH₄⁺ and NO₃^- on EOF 2, suggesting an additional source of nitrogen, likely from biogenic emissions of terrestrial ecosystems. Over the past millennium, the EOF 2 series has relatively high values around 1300 CE and 1600 CE, and has increased significantly since the Industrial Revolution. These variations are likely driven by temperature-dependent biogenic emissions on the Tibetan Plateau. Analyses of seasonal air mass backward trajectories and wind fields find that the chemical concentrations in the ZK ice core are mostly influenced by the westerly, but South Asia summer monsoon plays an important role in the transport of nitrogen species generated from biogenic emissions. This is further confirmed by the significant correlation between EOF 2 series and the South Asian summer monsoon index. This study provides new insight into the preindustrial sources, natural variabilities and major drivers of nitrogen deposition on the Tibetan Plateau.

Keywords: Atmospheric deposition; Climate variability; Ice core; Nitrogen species; Tibetan Plateau.

MeSH terms

Air Pollutants* / analysis
Ecosystem
Environmental Monitoring
Nitrogen* / analysis
Tibet

Substances

Air Pollutants
Nitrogen