Dissolved inorganic carbon budget of two alpine catchments in the central Tibetan Plateau: Glaciation matters

Zhengliang Yu; Jianhong Li; Guangjian Wu; Dongmei Qu; Fei Wang; Xiaoxing Ming; Haiying Qiu; Zhu Liu; Philipp Maurischat

doi:10.1016/j.scitotenv.2023.165191

Dissolved inorganic carbon budget of two alpine catchments in the central Tibetan Plateau: Glaciation matters

Sci Total Environ. 2023 Nov 10:898:165191. doi: 10.1016/j.scitotenv.2023.165191. Epub 2023 Jun 28.

Authors

Zhengliang Yu¹, Jianhong Li², Guangjian Wu³, Dongmei Qu¹, Fei Wang⁴, Xiaoxing Ming⁵, Haiying Qiu¹, Zhu Liu⁶, Philipp Maurischat⁷

Affiliations

¹ State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China.
² Key Laboratory of Karst Dynamics, MNR & Guangxi, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China.
³ State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China. Electronic address: wugj@itpcas.ac.cn.
⁴ School of Life Science, Shanxi Normal University, Taiyuan 030031, China.
⁵ State Key Laboratory of Biogeology and Environmental Geology, School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China.
⁶ College of Civil Engineering and Architecture, Hunan Institute of Science and Technology, Yueyang 414000, China.
⁷ Institute of Biology and Environmental Sciences (IBU), Carl von Ossietzky University of Oldenburg, 26129 Oldenburg, Germany.

PMID: 37391134
DOI: 10.1016/j.scitotenv.2023.165191

Abstract

Dissolved inorganic carbon (DIC) fluxes account for over one-third of the total carbon transported in most rivers. The DIC budget for glacial meltwater of the Tibetan Plateau (TP), however, is still poorly understood, despite the fact, the TP has the largest glacier distribution outside of the Poles. In this study, the Niyaqu and Qugaqie catchments in the central TP were selected to examine the influence of glaciation on the DIC budget in vertical evasion (CO₂ exchange rate at the water-air interface) and lateral transport (sources and fluxes) from 2016 to 2018. Significant seasonal variation in DIC concentration was found in the glaciated Qugaqie catchment, but was absent in the not glaciated Niyaqu catchment. δ¹³C_DIC showed seasonal changes for both catchments, with more depleted signatures during the monsoon season. The average CO₂ exchange rates in river water of Qugaqie were ~8 times lower compared to Niyaqu with values of -1294.6 ± 438.58 mg/m²/h and -163.4 ± 581.2 mg/m²/h, respectively, indicating that proglacial rivers can act as a substantial CO₂ sink due to CO₂ consumption by chemical weathering. DIC sources were quantified via the MixSIAR model using δ¹³C_DIC and ionic ratios. During the monsoon season, the contribution from carbonate/silicate weathering driven by atmospheric CO₂ was 13-15 % lower, while biogenic CO₂ involved in chemical weathering was 9-15 % higher, indicating a seasonal control on weathering agents. Carbonate dissolution driven by H₂SO₄/HNO₃ was the most important contributor to DIC in both catchments (40.7 ± 2.2 % in Niyaqu and 48.5 ± 3.1 % in Qugaqie). The net CO₂ consumption rate in the not glaciated Niyaqu catchment was close to 0 (-0.07 ± 0.04 × 10⁵ mol/km²/y), indicating the carbon sink effect caused by chemical weathering in this area was weak. The net CO₂ consumption rate in the glaciated Qugaqie catchment, however, was much lower than that in the not glaciated catchment with a value of -0.28 ± 0.05 × 10⁵ mol/km²/y. This study highlights that chemical weathering in small glaciated catchments of the central TP plays an active role in releasing CO₂ to the atmosphere.

Keywords: CO(2) exchange rate; Chemical weathering; Cryosphere; DIC; High Asia.