The glacial–terrestrial–fluvial pathway: A multiparametrical analysis of spatiotemporal dissolved organic matter variation in three catchments of Lake Nam Co, Tibetan Plateau

authored by

Philipp Maurischat, Lukas Lehnert, Vinzenz H.D. Zerres, Tuong Vi Tran, Karsten Kalbitz, Åsmund Rinnan, Xiao Gang Li, Tsechoe Dorji, Georg Guggenberger

Abstract

The Tibetan Plateau (TP) is a sensitive alpine environment of global importance, being Asia's water tower, featuring vast ice masses and comprising the world's largest alpine grasslands. Intensified land-use and pronounced global climate change have put pressure on the environment of the TP. We studied the tempo-spatial variability of dissolved organic matter (DOM) to better understand the fluxes of nutrients and energy from terrestrial to aquatic ecosystems in the TP. We used a multiparametrical approach, based on inorganic water chemistry, dissolved organic carbon (DOC) concentration, dissolved organic matter (DOM) characteristics (chromophoric DOM, fluorescence DOM and δ

¹³C of DOM) in stream samples of three catchments of the Nam Co watershed and the lake itself. Satellite based plant cover estimates were used to link biogeochemical data to the structure and degradation of vegetation zones in the catchments. Catchment streams showed site-specific DOM signatures inherited from glaciers, wetlands, groundwater, and Kobresia pygmaea pastures. By comparing stream and lake samples, we found DOM processing and unification by loss of chromophoric DOM signatures and a change towards an autochthonous source of lake DOM. DOM diversity was largest in the headwaters of the catchments and heavily modified in terminal aquatic systems. Seasonality was characterized by a minor influence of freshet and by a very strong impact of the Indian summer monsoon on DOM composition, with more microbial DOM sources. The DOM of Lake Nam Co differed chemically from stream water samples, indicating the lake to be a quasi-marine environment in regards to the degree of chemical modification and sources of DOM. DOM proved to be a powerful marker to elucidate consequences of land use and climatic change on biogeochemical processes in High Asian alpine ecosystems.

Organisation(s)

Institute of Soil Science
Institute of Fluid Mechanics and Environmental Physics in Civil Engineering

External Organisation(s)

Ludwig-Maximilians-Universität München (LMU)
University of Copenhagen
Chinese Academy of Sciences (CAS)
Technische Universität Dresden
Lanzhou University

Type

Article

Journal

Science of the Total Environment

Volume

838

Pages

156542

No. of pages

ISSN

0048-9697

Publication date

10.09.2022

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Pollution, Waste Management and Disposal, Environmental Engineering, Environmental Chemistry

Sustainable Development Goals

SDG 14 - Life Below Water, SDG 15 - Life on Land, SDG 13 - Climate Action

Electronic version(s)

https://doi.org/10.1016/j.scitotenv.2022.156542 (Access: Open)