The primary objectives of the study were to: (i) determine OM quantity and quality in the sediments of alpine lakes on the Tibetan Plateau, (ii) identify the primary environmental regulators of OM quantity and quality, and (iii) reveal OM transformations in the water column and sediments.

Firstly, we collected sediments and lake water from 20 lakes with diverse morphology and sizes across the entire Tibetan Plateau.

Secondly, We analyzed the bulk sedimentary OM and two leachable pools of the sedimentary OM, i.e., water-soluble OM and alkaline-extracted OM combining elemental and stable isotopic analysis, optical measurements (i.e., absorbance and fluorescence spectroscopy), and ultrahigh-resolution molecular techniques (i.e., electrospray ionization-assisted Fourier transform-ion cyclotron resonance mass spectrometry, ESI FT-ICR MS). We also measured the lake water physicochemical characteristics (i.e., depth, transparency, salinity, turbidity, DO, pH, TN, TP and Chl a), as well as the composition of dissolved OM in water column via optical measurements.

Thirdly, we performed statistical analysis to determine the primary environmental control and predictors of the spatial variability in sedimentary OM on the Tibetan Plateau. The statistical analysis included non-parametric Kruskal-Wallis with Dunn post hoc test, redundancy analysis, and linear regression models.

Main results of the study are that (i) sedimentary water-soluble OM and alkaline-extracted OM were both dominated by low-molecular-weight, low-aromaticity compounds with low contributions of terrestrial humic substances, suggesting that sedimentary leachable OM was primarily regulated by in-lake sources and processes; (ii) water depth, water transparency, and total phosphorus concentration in water column explained ~50% variance of sedimentary bulk and leachable OM, substantiating the importance of autochthonous sources and primary productivity in regulating the quantity and quality of sedimentary OM; (iii) in comparison to lake surface water DOM, water-soluble OM and alkaline-extracted OM from sediments had higher proportions of terrestrial humic-like substances, suggesting preferential preservation of allochthonous materials in the sediments.

The readme file contains an explanation of each of the variables in the dataset, its measurement units, and -if it concerns a derived variable (displayed in grey) - the way it was calculated from the primary data (displayed in black). #NA = values not available. Information on how the measurements were done can be found in the associated manuscript referenced above.