Carbonate Protection Regulates Effective Preservation of Labile Active Substances over a Centennial Time Scale in a Carbonate-Type Lake

Abstract

In lake ecosystems, the carbonate–organic matter interaction forms a selective protective effect on specific organic matter. The key to understanding the selective protection mechanism of carbonates is to clarify the compositional characteristics of organic matter under carbonate regulation. In this study, sediment from Daru Co Lake on the Qinghai–Tibet Plateau was used as the research object, and the molecular structural characteristics of organic matter buried by carbonates were determined using high-resolution mass spectrometry and X-ray photoelectron spectroscopy (XPS). The results showed that, over the nearly 100 year period (1928–2015), the main components of organic matter buried by carbonates included not only the classically refractory macromolecule lignin (32.2%) but also labile active substances, such as proteins (29.1%) and lipids (18.8%). This results suggests that, in carbonate lake environments, carbonates can actively capture labile organic matter and form stable associations, allowing labile organic matter to undergo long-term geological sequestration under the protection of inorganic minerals instead of being inevitably rapidly mineralized.