The role of mineral mediation in organic carbon preservation and phosphorus removal in saline lake sediments of the Tibetan Plateau

Abstract

The dual role of minerals in preserving organic carbon (OC) and immobilizing phosphorus (P) is increasingly acknowledged, yet how these functions co-evolve under extreme geochemical conditions remains poorly understood. Here, we investigate surface sediments from Qinghai Lake, the largest saline lake in China, to elucidate mineral-mediated mechanisms regulating coupled C-P dynamics. Using a Bayesian model, we demonstrate that autochthonous OC constitutes 29% to 40%, with allochthonous OC undergoing widespread lateral transport, particularly in the southern basin. Clay minerals exhibit superior preservation capacity for OC, as evidenced by a strong correlation between OC content and mineral surface area. P speciation analysis reveal that 93 % of sedimentary P is present as thermodynamically stable calcium-bound forms, driven by carbonate co-precipitation processes. These synergistic mineral-mediated interactions not only enhance OC stability but also suppress internal P recycling, offering a natural buffering mechanism against eutrophication. Our findings provide new insight into the biogeochemical coupling of C and P in saline lakes and propose a novel framework for mitigating nutrient loading and greenhouse gas emissions in high-altitude aquatic systems.