Chemical weathering and CO₂ consumption in the glaciated Karuxung River catchment, Tibetan Plateau

Abstract

Climate factors play critical roles in controlling chemical weathering, while chemically weathered surface material can regulate climate change. To estimate global chemical weathering fluxes and CO 2 balance, it is important to identify the characteristics and driving factors of chemical weathering and CO 2 consumption on the Tibetan Plateau, especially in glaciated catchments. The analysis of the hydro-geochemical data indicated that silicate weathering in this area was inhibited by low temperatures, while carbonate weathering was promoted by the abundant clastic rocks with fresh surfaces produced by glacial action. Carbonate weathering dominated the riverine solute generation (with a contribution of 58%, 51%, and 43% at the QiangYong Glacier (QYG), the WengGuo Hydrological Station (WGHS), and the lake estuary (LE), respectively). The oxidation of pyrite contributed to 35%, 42%, and 30% of the riverine solutes, while silicate weathering contributed to 5%, 6%, and 26% of the riverine solutes at the QYG, WGHS, and LE, respectively. The alluvial deposit of easily weathering fine silicate minerals, the higher air temperature, plant density, and soil thickness at the downstream LE in comparison to upstream and midstream may lead to longer contact time between pore water and mineral materials, thus enhancing the silicate weathering. Because of the involvement of sulfuric acid produced by the oxidation of pyrite, carbonate weathering in the upstream and midstream did not consume atmospheric CO 2 , resulting in the high rate of carbonate weathering (73.9 and 75.6 t km À2 yr À1 , respectively, in maximum) and potential net release of CO 2 (with an upper constraint of 35.6 and 35.2 t km À2 yr À1 , respectively) at the QYG and WGHS. The above results indicate the potential of the glaciated area of the Tibetan Plateau with pyrite deposits being a substantial natural carbon source, which deserves further investigation. K E Y W O R D S chemical weathering, CO 2 consumption, glaciated catchments, pyrite oxidation, Tibetan Plateau 1 | INTRODUCTION Climate factors such as air temperature and precipitation play critical roles in controlling chemical weathering, while the mineral byproducts from the chemical weathering of surface material can regulate climate change (Berner et al., 2003;Godsey et al., 2019). Chemical weathering and climate warming are coupled via a potential negative feedback process-that is, mineral dissolution and chemical weathering of rocks

Chemical weathering rates and controlling mechanisms of glacial catchments within different climate regimes in the Tibetan Plateau

“…Therefore, before calculating the weathering rates, the contribution of precipitation to dissolved loads needs to be deducted. Due to the lack of precipitation data in the study areas, the precipitation data in the Tingri and Nyalam counties ( Yang et al, 2011 ) and the Langkazi ( Zhang et al, 2021 ) were used as the precipitation end-member of the Chaiqu catchment. The chemical composition of precipitation ( Liu et al, 2013a ; Wang et al, 2019 ) in Sejila Mountain were used to replace the precipitation end-member of the Niangqu catchment.…”

“…However, research on the weathering in the YTRB’s glacial areas is still limited. Previous studies have primarily focused on temperate glacier areas in the southeastern TP and the Himalayas ( Biswal et al, 2022 ; Hasnain, Subramanian & Dhanpal, 1989 ; Hasnain & Thayyen, 1996 ; Hodson et al, 2002 ; Jiang et al, 2018 ; Li et al, 2019 ; Liu et al, 2022 ; Shukla et al, 2018 ; Singh, Keshari & Ramanathan, 2020 ; West et al, 2002 ; Zhang et al, 2021 ). Few studies have been carried out in the TP’s cold glacier areas ( Wu, 2018 ; Yu et al, 2019 ; Yu et al, 2021a ; Yu et al, 2021b ), and there is a lack of research on the chemical weathering mechanisms of glacial areas in the YTRB.…”

“…Due to the complexity of the weathering process, many factors could influence this process, and there may be interactions between the controlling factors. Some studies have revealed how lithology and land use types affects weathering ( Hakim et al, 2021 ; Hartmann et al, 2014 ; Zhang et al, 2021 ), whereas others have emphasized the impact of climate and tectonics ( Gernon et al, 2021 ; West, Galy & Bickle, 2005 ). Therefore, it has always been challenging to understand the relationships between controlling factors and to clarify the relative importance of each controlling factor in the study of weathering mechanisms.…”

“… Bufe et al (2022) found that carbonate weathering is impacted by denudation rate, while silicate weathering is not, based on the investigations of small catchments in the eastern TP. Zhang et al (2021) proposed that silicate weathering was inhibited by low temperatures while a large amount of freshly ground rock debris produced by glacial erosion enhanced carbonate weathering in the Karuxung River catchment. Jiang et al (2018) revealed that lithology, climatic factors, and physical erosion rate are the critical parameters controlling chemical weathering rate by studying the small catchments of the Gongga Mount.…”

CO2 Consumption Rates in the Glacierized Himalayan Headwaters: The Importance of Sulfuric and Nitric Acid‐Mediated Chemical Weathering Reactions in Geologic Carbon Cycle

“…Previous studies have produced a significant body of information on the role of H 2 CO 3 and H 2 SO 4 acids on rock weathering processes (Biswal et al., 2022; W. Liu et al., 2023; Shukla et al., 2018; Singh & Kumar, 2022; Torres et al., 2014, 2017; Wolff‐Boenisch et al., 2009; Zhang et al., 2021). However, the role of HNO 3 on chemical weathering processes is critically underexplored—for example, it is entirely missing in the Himalayan region—but crucial to understanding the variability in the carbon cycle over multimillion‐year time scales.…”