Characterization, sources and transport of dissolved organic carbon and nitrogen from a glacier in the Central Asia

Tanguang Gao; Shichang Kang; Yulan Zhang; Michael Sprenger; Feiteng Wang; Wentao Du; Xiaoming Wang; Xiaoxiang Wang

doi:10.1016/j.scitotenv.2020.138346

Characterization, sources and transport of dissolved organic carbon and nitrogen from a glacier in the Central Asia

Sci Total Environ. 2020 Jul 10:725:138346. doi: 10.1016/j.scitotenv.2020.138346. Epub 2020 Apr 3.

Authors

Tanguang Gao¹, Shichang Kang², Yulan Zhang³, Michael Sprenger⁴, Feiteng Wang⁵, Wentao Du⁵, Xiaoming Wang⁵, Xiaoxiang Wang⁵

Affiliations

¹ Key Laboratory of Western China's Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China.
² Key Laboratory of Western China's Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China; State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; CAS Centre for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China.
³ State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; CAS Centre for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China. Electronic address: yulan.zhang@lzb.ac.cn.
⁴ Institute for Atmospheric and Climate Science, ETH Zurich, CH-8092 Zurich, Switzerland.
⁵ State Key Laboratory of Cryospheric Science, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.

PMID: 32302834
DOI: 10.1016/j.scitotenv.2020.138346

Abstract

Glacier melting represents an important flux of carbon and nitrogen (N) and affects the hydrological cycle. In this study, we presented the features of dissolved organic carbon (DOC) and N concentrations, their potential sources and export from the Muz Taw glacier in Central Asia. The average DOC and total dissolved nitrogen concentrations were 1.12 ± 1.66 and 0.62 ± 0.59 mg L^-1 in surface snow and 0.21 ± 0.04 and 0.31 ± 0.10 mg L^-1 in snowpit samples, respectively. The values from snowpit of the Muz Taw glacier were comparable to data reported from glaciers in the Tibetan Plateau but were considerably higher than those from polar regions. The C/N ratios in snow ranged from 0.7 to 11.7, indicating the high bioavailability of DOC. Mass absorption cross section of DOC at 365 nm in snow indicated that during the snow melting process, light-absorbing DOC was prone to be attached to particles, especially in the ablation zone of the Muz Taw glacier. Radiative forcing caused by DOC contributed approximately 38 ± 26% and 18 ± 9.8% of that caused by black carbon for surface snow and snowpit samples, respectively. DOC and N deposition on the glacier surface were influenced by the combined sources from anthropogenic input, wild biomass burning emission, and dust input from local regions and long range transport. Export of DOC and N from the Muz Taw glacier was estimated to be 3.47-18.5 t C yr^-1 and 5.11-10.23 t N yr^-1 respectively, based on their concentrations and current glacier mass balance. These results enhanced our understanding of the sources and cycle of DOC and N released from glaciers in Central Asia, where glacier meltwater can protect the population from drought stress.

Keywords: Central Asia; Dissolved organic carbon; Glacier melt; Radiative forcing; Total dissolved nitrogen.